DART 200 CDPD Modem
For CDPD Versions 1.0 and 1.1
User’s Guide
Firmware Version 3.0.10
Revision 1.0
Part Number: 1197-00
January 1998
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DART 200 CDPD Modem User’s Guide
Important Notice
The Data Access Radio Transceiver (DART) can only be exported from the US, or re-exported to another country with the
issuance of an export license from the US Government. Contact Sierra Wireless for more information.
Because of the nature of wireless communications, transmission and reception of data can never be guaranteed. Data can be
delayed, corrupted, or be totally lost. Although significant delays or losses of data are rare when wireless devices such as DART
are used in a normal manner with a well-constructed network. DART should not be used in situations where failure to transmit or
receive data could result in damage of any kind to the user or any other party, including but not limited to personal injury, death,
or loss of property. Sierra Wireless, Inc., accepts no responsibility for damages of any kind resulting from delays or errors in data
transmitted or received using DART, or for failure of DART to transmit or receive such data.
Contact Information
Sierra Wireless, Inc.
260 - 13151 Vanier Place, Richmond, BC, Canada V2V 2J2
Tel. 604.231.1100 or 313.528.5880
Fax. 604.231.1109
Email: [email protected]
Web site: www.sierrawireless.com
Part Number: 1197-00, Revision 1.0
© 1997 Sierra Wireless, Inc. All rights reserved.
Printed in Canada.
First Printing: January, 1998.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without
the prior permission of the publisher.
AT is a trademark of Hayes Microcomputer Products, Inc.
Hayes is a registered trademark of Hayes Microcomputer Products, Inc.
All other trademarks are owned by their respective companies.
The information in this guide is subject to change without notice and does not represent a commitment on the part of Sierra
Wireless, Inc. Sierra Wireless, Inc. shall not be liable for incidental or consequential damages resulting from the furnishing,
performance, or use of this manual
Safety and Hazards
Do not operate the Sierra Wireless modem in areas where blasting is in progress, where explosive atmospheres may be present,
near medical equipment, near life support equipment, or any equipment which may be susceptible to any form of radio
interference. In such areas, the Sierra Wireless modem MUST BE TURNED OFF. The Sierra Wireless modem can transmit
signals which could interfere with this equipment.
Do not operate the Sierra Wireless modem in any aircraft, whether the aircraft is on the ground or in flight. In aircraft, the Sierra
Wireless modem MUST BE TURNED OFF. The reason for this is that when operating in the CDPD or cellular circuit switched
mode, the Sierra Wireless modem can transmit signals which could interfere with various onboard equipment systems.
The driver or operator of any vehicle should not operate the Sierra Wireless modem while in control of a vehicle. Doing so will
detract from the driver or operator’s control and operation of that vehicle. In some states and provinces, operating such
communications devices while in control of a vehicle is an offence.
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DART 200 CDPD Modem User’s Guide
Contents
Figures
Tables
xi
xii
About This Guide
xiii
xiii
xiii
xiii
xiv
xv
Who should read this guide
Skills required to use this guide
What is in this guide
Changes and additions to this guide
Related reading
Compliances
FCC
Canadian
xvi
xvi
xvi
Safety information
xvii
xvii
Conventions used in this guide
1
Introduction
Description
1-1
1-1
1-2
New for this version
DART 200 accessories and services
RF accessories
Power accessories
Hardware options
Software options
1-2
1-2
1-2
1-2
1-2
1-2
Services
Migration considerations
Contacting your cellular carrier
1-2
1-3
CDPD network overview
AT command set summary
1-3
1-4
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DART 200 CDPD Modem User's Guide
2
Installation and Setup
2-1
Field installation
2-1
2-1
2-2
2-4
Physical installation considerations
Antenna considerations
Troubleshooting
Getting started
Modem setup
Basic modem personalization
Selecting CDPD 1.0 or 1.1 mode of operation
2-5
2-5
2-6
2-8
Initial testing
Setup verification
2-8
2-8
Register representation
Channel acquisition
Problem determination
Registration
Troubleshooting registration failure
Basic communications
2-9
2-10
2-12
2-15
2-17
2-21
3
4
CDPD Security Features
Airlink security
3-1
3-1
3-1
3-2
Authentication services
Modem security management
Broadcast and Multicast Operation
4-1
4-1
4-2
Overview
Broadcast
Multicast
4-2
Multicast setup
4-3
5
DART Supported Protocols
5-1
UDP
5-1
5-2
5-2
5-4
5-5
5-6
Basic UDP characteristics
Basic UDP communication
Basic UDP setup options
UDP server characteristics
UDP server setup options
Sample UDP server setups
Remote UDP setup
Host UDP setup
11
5-11
5-12
TCP
5-14
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DART TCP capabilities
Friends Only mode operation
TCP communication
Setup options
5-14
5-14
5-15
5-17
Sample TCP setups
Remote TCP setup
Host TCP setup
5-19
5-19
5-21
SLIP
5-22
5-22
5-24
5-26
5-27
Modem setup for SLIP
SLIP IP Address overview
SLIP operation
SLIP initial testing
Telnet
Setup options
Telnet escape commands
New for this version
Binary mode considerations
Telnet operation
5-28
5-28
5-30
5-31
5-31
5-31
6
Device Attachment
RS-232 connection
6-1
6-1
6-1
Null modem function
7
8
Vehicle Installation Considerations
Electrical transients
7-1
7-1
7-1
7-2
Application considerations
Proximity to other antennas
Application Programming
8-1
AT Command Set Support
8-1
Device drivers
8-2
Application program structure
DART setup
Network connection
Data transfer
Modes of operation
Error recovery
8-2
8-2
8-2
8-3
8-3
8-4
Automatic registration
Registration timer
Manual registration
Auto-Registration at power-on
Auto-Registration when not registered
8-6
8-7
8-7
8-7
8-8
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DART 200 CDPD Modem User's Guide
Auto-Registration/De-Registration at connection/disconnection 8-8
Deregistration
8-8
Data forwarding
Manual transmit control
8-8
8-9
Automatic transmit control
Maximum packet size transmit control
Escape transmit control
8-9
8-10
8-11
8-11
Usage considerations (for TCP and UDP)
Auto answer setup
8-11
Flow control considerations
Flow control and the new end-user
Flow control in application (online) mode
Hardware flow control operation
PAD operating mode
8-12
8-13
8-13
8-14
8-14
Data and control interface
CDPD status sensing
Escaping through the control interface
8-15
8-15
8-16
Binary data transfer
Flow control considerations
Data forwarding considerations
8-16
8-17
8-17
Parity considerations
8-17
PAD keep-alive considerations
Timer expiry in transmit mode
Timer expiry in receive mode
Timer expiry for keep-alives
8-18
8-19
8-19
8-19
Escape sequence considerations
Command response options
Echo option selection
8-20
8-20
8-21
8-22
8-22
8-23
8-24
Channel acquisition restrictions
Baud considerations
Maximum block size considerations
Modem dial directory
Messages and response codes
8-25
Messages
8-25
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DART 200 CDPD Modem User’s Guide
A Limited Warranty and Service
Limited warranty
A-1
A-1
A-1
Service
B Product Specifications
B-1
Power requirements
Mobile
Stationary
Peak
Power cable
Size
B-1
B-1
B-1
B-1
B-1
B-1
B-1
B-1
B-1
B-1
B-1
B-1
B-1
B-1
B-2
B-2
Weight
Operating environment
RF power output
Frequency range
Data rates
Antenna
Antenna cable
Data connection
Data cable
Protocols
C Charts and Diagrams
C-1
D-1
D SLIP Setup Examples
Trumpet
D-1
Installation and startup
Windows 95
D-1
D-3
E S-Registers
E-1
Register display formats
Registers 0 through 99 formats
Register 100 through 126 formats
E-1
E-2
E-2
Register definitions
E-3
F DART AT Command Set
AT command set usage
F-1
F-1
F-1
Basic AT commands
Service Provider commands
F-24
Clearing BLOCKED status
F-25
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DART 200 CDPD Modem User's Guide
G Loading DART 200 Firmware
G-1
Firmware download procedure
G-1
H Problem Sheet
H-1
Glossary
Acronyms
Terms
Glossary-1
Glossary -1
Glossary-8
Index
Notes
Index-1
Notes-1
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Figures
Figure 1-1. DART 200 front view
Figure 2-1. Installing DART 200 with mounting bracket
Figure 2-2. S-Register bit positions
1-1
2-2
2-9
Figure 2-3. Viewing the network S-Register (S57)
Figure 2-4. Monitoring the CDPD channel
Figure 2-5. Viewing registration status with ATS57?
Figure 4-1. Checking NEI status with AT\S?
Figure 5-1 Terminal connection to a CDPD network using SLIP
Figure 6-1. Standard RS-232 connection
Figure 6-2. Stand-alone RS-232
2-13
2-13
2-15
4-3
5-25
6-1
6-2
Figure 6-3. Null modem location
6-2
Figure 8-1. Viewing the IP Address directory
Figure C-1. Mounting bracket template
Figure C-2. Modem connector pinout
8-24
C-1
C-1
E-3
Figure E-1. S-Register bit positions
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DART 200 CDPD Modem User’s Guide
Tables
Table 1-1. Basic AT command set
Table 1-2. Service Provider AT command set
Table 2-1. S-Registers above 100
Table 2-2. Registration failure troubleshooting
Table 3-1. Key types
1-5
1-6
2-14
2-17
3-2
Table 5-1. Remote UDP setup
Table 5-2. Host UDP setup
Table 5-3. Remote TCP setup
Table 5-4. Host TCP setup
Table 6-1. Typical null modem pinout
Table 8-1. Telemetry options for PAD Mode
Table C-1. Pin functions
5-11
5-13
5-20
5-21
6-2
8-15
C-2
Table C-2. RS-232 signal interface
C-2
Table E-1. S-Register digits
E-2
Table E-2. Register summary
E-3
Table F-1. Commands beginning with letters
Table F-2. Commands beginning with ampersand (&)
Table F-3. Commands beginning with backslash (\)
Table F-4. Commands beginning with asterisk (*)
Table F-5. Enable/Disable Service Provider mode
Table F-6. Service Provider commands beginning with caret (^)
Table F-7 Service Provider commands beginning with dash (-)
F-2
F-9
F-13
F-18
F-24
F-25
F-29
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About This Guide
Who should read this guide
This User’s Guide is designed to assist application software developers
with setup, installation, testing, and design of applications for the Data
Access Radio Transceiver (DART) 200.
Skills required to use this guide
The reader requires a basic working knowledge of Transmission Control
Protocol/Internet Protocol (TCP/IP) and the use of the Attention (AT)
command set to use this guide.
What is in this guide
This guide provides information and assistance for both physical
installation and programming of the DART.
This guide is composed of eight chapters, eight appendixes, a glossary
and an index.
Chapter 1, Introduction, describes new features for version 3.0.10, how
to migrate from previous versions, and Cellular Digital Packet Data
(CDPD) network information. Also, the AT command set is summarized
in this chapter.
Chapter 2, Installation and Setup, provides the basic information needed
to install, setup, and test the modem on the CDPD network.
Chapter 3, CDPD Security Features, discusses security features such as
airlink security, authentication services, and modem security
management.
Chapter 4, Broadcast and Multicast Operation, discusses the CDPD
broadcast and multicast functions.
Chapter 5, DART Supported Protocols, discusses and gives set up
instructions for the communication protocols supported by the DART,
including User Datagram Protocol (UDP), Transmission Control
Protocol (TCP), Serial Line Interface Protocol (SLIP), and telnet. The
TCP and UDP sections include sample setups for each of the protocols.
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DART 200 CDPD Modem User’s Guide
About This Guide
Chapter 6, Device Attachment, describes the RS-232 interface to the
DART, what a null modem is, and how to determine if one is required.
Chapter 7, Vehicle Installation, discusses the items to consider when
installing the DART 200 in a vehicle.
Chapter 8, Application Programming, describes the AT command set to
use with the DART in detail, presents command usage considerations,
and provides additional information for planning and designing CDPD
applications for the TCP and UDP environments.
Appendix A, Limited Warranty and Service, gives important warranty
information and instructions for getting service.
Appendix B, Product Specifications, summarizes the physical, electrical,
and environmental specifications for the DART 200.
Appendix C, Charts and Diagrams, provides the DART mounting
bracket template and the modem connector pinout figure.
Appendix D, SLIP Setup Examples, gives a setup example for the
Trumpet Winsock and directions for getting Windows 95 support.
Appendix E, S-Registers, lists the Status (S)-Registers supported by the
DART 200 and describes their function and usage.
Appendix F, DART AT Command Set, lists all the DART AT commands
and provides detailed descriptions of their function and usage.
Appendix G, Loading DART Firmware, describes how to update DART
200 firmware.
Appendix H, Problem Sheet, provides a Sierra Wireless form for
submitting problems to be resolved.
Glossary
Index
Changes and additions to this guide
For those readers familiar with the DART 200 User's Guide, the
following items have been added or enhanced:
·
Migration considerations, p. 1-2
·
·
·
·
·
Anntena grounding caution, p. 2-3
Registration progress status in Registration, p. 2-15 and p. 8-6
Improved description of Modem security management, p. 3-1
Sample UDP setups, p. 5-11
Ability to get client's IP Address and port in bullet point UDP server
communication, p.5-8 and in TCP communication, p. 5-15
·
Friends Only mode operation, p. 5-14
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DART 200 CDPD Modem User’s Guide
About This Guide
·
Sample TCP setups, p. 5-19
·
·
·
·
·
·
·
Automatic SLIP restart bullet point, p. 5-24
Telnet operation, p. 5-31
Maximum packet size transmit control, p. 8-9
Escape transmit control, p. 8-10
Hardware flow control operation, p. 8-13
PAD operating mode, p. 8-14
RS-232 signal levels and states, in Table C-2, RS-232 signal
interface, p. C-2
·
·
·
·
·
·
Channel acquisition restrictions, p. 8-21
Modem dial directory, p. 8-24
Message and response codes, p. 8-25
Windows 95, p. D-3
Clearing BLOCKED status, F-25
Index, p. I-1
Related reading
Additional information regarding the CDPD network and communication
information can be found in the following references:
·
Cellular Digital Packet Data System Specification, CDPD Forum,
401 N. Michigan Ave., Chicago, IL 60611, (tel.) 800.335.CDPD
·
TCP/IP, Running a Successful Network, K. Washburn and J.T.
Evans, NY, Addison-Wesley, 1993
·
·
Internetworking with TCP/IP, D.E. Comer, N.J., Prentice Hall, 1991
The Whole Internet, E. Krol, Sabastopol, CA, 1992,
(tel.) 800.998.9938
·
Computer Networks, A.S. Tannenbaum, N.J., Prentice Hall, 1989
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Compliances
FCC
This equipment has been tested and found to comply with the limits for a
Class B digital device, pursuant to Part 15 of the FCC rules. These limits
provide reasonable protection against harmful interference in residential
installations. This equipment generates, uses and can radiate radio
frequency energy and, if not installed and used in accordance with the
instructions, can cause harmful interference to radio communications.
However, there is no guarantee that interference will not occur in a
particular installation. If this equipment does cause harmful interference
to radio or television reception, determined by turning the equipment off
and on, try to correct the interference by one or more of the following
measures:
?
NOTE:
This unit was tested
with shielded cables on
the peripheral devices.
Shielded cables must be
used with the unit to
insure compliance.
·
Reorient or relocate the receiving antenna
·
·
Increase the separation between the equipment and receiver
Connect the equipment to an outlet on a circuit different from the
circuit the receiver is connected to
·
Consult the dealer or an experienced radio/TV technician for help
Changes or modifications not expressly approved by the manufacturer
can void the user’s authority to operate the equipment.
?
NOTE:
The manufacturer is
not responsible for any
radio or TV
interference caused by
unauthorized
Canadian
“This digital apparatus does not exceed the Class B limits for radio noise
emissions from digital apparatus as set out in the interference causing
equipment standard entitled ‘Digital Apparatus’, ICES-003 of the
Department of Communications.”
modifications to this
equipment. Such
modification could void
the user’s authority to
operate the equipment.
“Cet appareil numerique respecte les limites de bruits radioelectriques
applicables aux appareils numeriques de Classe B prescrites dans la
norme sur le materiel brouilleur: ‘Appareils Numeriques’, NHB-003
edictee par le ministre des Communications.”
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DART 200 CDPD Modem User’s Guide
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Safety information
A caution in the margin, as shown at the left or in the body of the text,
denotes a procedure or practice if not performed correctly could result in
loss of data, or damage to equipment.
CAUTION:
A caution calls
attention to a procedure
or practice if not
performed correctly
could result in loss of
data or damage to
equipment.
A warning in the margin, as shown at the left or included within the body
of the text denotes a hazard. A caution calls attention to a procedure or
practice if not performed correctly could result in personal injury.
WARNING:
Denotes a hazard. A
warning calls attention
to a procedure or
practice if not
performed correctly
could result in personal
injury.
Conventions used in this guide
The following conventions are used in this guide to help readers locate
and interpret information easily.
Italics
Italicized text is used for book titles, and for
cross-referencing chapter titles, and subsections
within chapters. In cross-references the most
specific item, usually, the last item, is italicized, for
example:
·
·
Chapter 1, Introduction
Chapter 1, Introduction, Description
Courier
Courier text is used to show on-screen text, for
example:
at\s?
* NEI 0 = IP ADDRESS 198.225.189.032
GMID 00000
OK
SMALL CAPS
Small capitals are used for key names, key
combinations, and key sequences, for example:
Press ENTER.
ALL CAPS
All capitals are used to show the connection states
of the DART, for example, CONNECT.
Bold text is used to emphasize the AT commands,
Bold
for example, AT\N.
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About This Guide
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Chapter
1
Introduction
Description
The Data Access Radio Transceiver (DART) 200, as shown in Figure
1-1, is a wireless, multipurpose, programmable modem that provides
reliable, cost effective mobile and fixed communications over the
Cellular Digital Packet Data (CDPD) network. It is a 3-watt, half-duplex
device operating on a regulated 12 volts @ 2.5 amps, and contains flash
memory to allow software upgrades to be made in the field. The DART
200 differs from its predecessor, the DART 100, in that it has the flash
memory to enable field download of software upgrades.
Figure 1-1. DART 200 front view
Data input
RS-232 DB-9
Connector
Power
connection
12VDC*
Power
Switch
Power On
indicator
and RSSI
*Molex Micro-Fit 3.0 4305-0200 - Mates with Molex 43025-0200 on
cable.
The modem is lightweight (only 12 ounces), with a small form factor
(6.3” x 3.4” x 1.0”). Its rugged construction makes it well suited for
industrial and commercial applications of all kinds.
The DART 200 firmware supports either CDPD V1.0 or CDPD V1.1.
The present version of the modem comes pre-selected for CDPD V1.1.
This selection can be altered by modifying an Status (S)-Register. Refer
to Selecting CDPD 1.0 or 1.1 mode of operation, p. 2-8, for details.
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1 Introduction
From a networking perspective, the modem has complete built-in
Transmission Control Protocol (TCP), User Datagram Protocol (UDP),
Serial Line Internet Protocol (SLIP), and telnet protocols. Network
communications can be achieved without the attached end-user device
having to provide an integrated TCP or UDP capability. Select the
desired built-in protocol included in the DART 200 by using the
appropriate AT dial command and begin your data transfer. The end-user
can put the DART 200 in SLIP mode, providing an external software
stack, if desired.
A power cord with connector is supplied with each DART 200, and one
copy of this User’s Guide is included with each order. A power supply
and cellular antennas are available as options at additional cost.
New for this version
If you have prior experience with the DART 200, major differences and
enhancements between the old modem software (3.0.9 dated 7/2/96 and
earlier) and the current version are:
·
Provides the “friends only” feature for TCP in addition to UDP
The automatic SLIP restart feature is now available
·
DART 200 accessories and services
RF accessories
·
·
3 dB cellular magnetic mount antenna
Power accessories
110 VAC to 12 VDC @2.5 amps power
supply
Hardware options
Software options
Services
·
Mounting bracket
·
V.42 bis data compression
Developers package
·
·
DART technical training
Migration considerations
If you are migrating applications from prior versions of the DART 200
software to the current version, there are no changes in this version that
alter existing application operation to be aware of. However, to use TCP
Friends Only mode or Auto SLIP restart, some alteration can be required.
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1 Introduction
Contacting your cellular carrier
There are currently two cellular carriers in each market area: the A side
carrier and the B side carrier. Each carrier can potentially install and
enable CDPD on their cellular network. The CDPD network allows
end-users to visit the regions of other carriers, as well as move within
their home cellular system.
Contact your cellular provider to get an IP Address for your modem.
This IP address lets you operate the modem on the CDPD network.
Although the modem can perform some basic functions without an IP
Address, it cannot register, ping, or run end-user applications. Your
carrier requires the Equipment Identifier (EID) of the DART 200 to give
you an IP Address.
?
NOTE:
The EID is found on
the label on the bottom
of your DART 200.
Ask your carrier for the following information:
·
·
·
Side of their operation (A or B)
IP Address
IP Address of a router or server to ping when you are testing
CDPD network overview
The CDPD system is an extensive communications system overlaying
the existing cellular voice network, as shown in Figure 1-2. It takes
advantage of the investments already made by cellular providers. By
adding CDPD to the network, packet data can be interspersed with voice
communications at an advantageous cost to the end-user.
Figure 1-2. CDPD network
M-ES
F-ES
MAS/
Host
MDBS
MDIS
CDPD
Modem
System
Public or Private
Packet Data Networks
Cellular Tower
The communication flow sequence includes:
1. Data packets transmitted from the Mobile End Station (M-ES) are
received at the cellular towers by Mobile Data Base Stations
(MDBSs)
2. Data packets are passed by the MDBS to the controlling Mobile Data
Intermediate System (MDIS)
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1 Introduction
3. Data packets are routed by the MDIS through the appropriate
network to the Fixed End System (F-ES), usually a host computer
over a public or private data network.
?
NOTE:
4. If a response is required from the F-ES, the process is reversed.
The role of the DART 200 in the CDPD network is to:
Either the M-ES or
F-ES can initiate
CDPD communication.
1. Accept commands and digital data from the end-user application
equipment through the RS-232 port.
2. Assemble the data into packets.
3. Encrypt the packets.
4. Transmit the encrypted data packet to the network.
The DART 200 also:
1. Receives packet data from the network.
2. Decrypts the packets.
3. Disassembles the packets to extract the application data.
4. Passes the serial data to the end-user’s application equipment
through the RS-232 port.
Airlink security, to prevent eavesdropping, is provided by encrypting the
data packets between the DART 200 and the MDIS. If end-to-end data
security is desired it must be implemented or otherwise provided by the
end-user.
The major cellular carriers and equipment manufacturers created a trade
group called the Wireless Data Forum (formerly the CDPD Forum), that
develops and publishes the governing technical specifications for, and
promotes the use of CDPD technology.
AT command set summary
The Basic and Service Provider AT command sets are listed in Tables
1-1 and 1-2 (pp. 1-5 and 1-6). The AT commands can be concatenated
(end-to-end or with a blank between commands) for up to a length of 80
characters including blanks, for example:
·
Normal command concatenation
·
ATE1V1&D0&S1\F3\N2
·
AT\S?S57?&V+
·
White space concatenation (for readability)
AT E1 V1 &D0 &S1 \F3 \N2
·
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DART 200 CDPD Modem User’s Guide
1 Introduction
Do not enter an AT command that requires a parameter without using
one, as the missing parameter defaults to zero. For example, if you
entered AT\N without a value in the range of 1 to 4, the command
defaults to AT\N0. The \N0 setting also forces \J1, causing channel
acquisition problems.
Similarly, the same thing can happen with concatenation. If you enter an
invalid command, such as AT\N?, the DART 200 assumes a
concatenation of AT\N and AT? The result is a display of the last
register referenced (due to the AT?) and to set \Nn to \N0.
Use caution when entering commands. If you get unexpected results,
display the register settings and modem profile with an AT&V command
to check there is no entry error.
?
NOTE:
Entering invalid AT
commands can cause
incorrect and
Table 1-1. Basic AT command set
A/
A
Repeat
Answer Online
unexpected results.
D
E
F
Dial (connection setup)
Command Mode Echo
Online Mode Echo
H
I
Hang-up (close connection)
Identify
O
Enter Online Mode
Q
Quiet Mode
S
Select Register
V
X
Z
Verbose Result Codes
Extended Result Codes
Soft Reset
?
=
Read Selected Register
Write Selected Register
Set DCD Operation
&C
&D
&E
&F
&L
&S
&V
&V+
&W
&Z
\F
Set DTR Operation
Escape Code Recognition On or Off
Restore Factory Defaults
Set DART Line Speed and Format
Set DSR Operation
View Active Profile
View Radio Resource status
Save Active Profile
Set or Display Dial Directory Entries
Set Data Forwarding Operation
Restrict Channel Selection
Manual Transmit Control
Set Side Preference
Select PAD or Telnet Operating Mode
Set, Enable or Disable PIN
Set Flow Control Operation
Network Registration Control
Set Subscriber Identity
Automatic Transmit Control
Select Server Type
\J
\M
\N
\O
\P
\Q
\R
\S
\T
*A
*B
Enable/Disable Reception of Broadcast Messages
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Table 1-1. Basic AT command set (cont.)
*C
*E
*G
*K
*L
*M
*P
*R
*S
*T
*U
Enable/Disable SLIP TCP Header Compression
Enable Network Connection with PIN
SLIP Multicast Address Selection
TCP PAD Keep Alive
Set Listen Port Number
Set MAS IP Address for SLIP
Ping Remote Host
Automatic SLIP Restart
Start SLIP (Serial Line IP) Mode
Telnet Keep Alive
Unblock Modem - Pin Access
Table 1-2. Service Provider AT command set
^A
^C
^F
^G
^H
^I
^L
^P
^S
-L
Set the IP Address of modem
Clear Blocked Status
Force PIN Usage
Set Multicast Group ID
Set Service Provider ID
Set Service Provider network ID
Set the Local Service Area ID
Enable/disable Supervisor Mode
Set the Modem SLIP Address
Set Channel Lock
-R
Software Reboot
-V
-Z
View Radio Resource Management Data
View Modem Credentials
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Chapter
2
Installation and Setup
Field installation
Physical installation considerations
The Data Access Radio Transceiver (DART) 200 is designed for both
stationary and mobile applications. The guidelines for modem
installation are:
P
TIP:
Use the optional
mounting bracket to
simplify the physical
installation, refer to
Figure C-1 for the
mounting bracket
template.
·
Environment - The standalone DART 200 is ruggedly constructed.
However, it is not waterproof, so do not locate the modem where it
can get wet. Also, refer to the humidity specification in Appendix B,
Product Specifications. If installing the DART 200 in a wet
environment, enclose it in a proper National Electrical
Manufacturer’s Association (NEMA) enclosure. Also, install the unit
where there is adequate ventilation to prevent possible overheating
·
·
·
Location - Installation with clear access to the unit is recommended
for viewing the LED, that indicates power and RF status, and for
accessing the RS-232 port for required personalization or
troubleshooting. Locate the DART 200, if possible, at least 2 feet
from personnel
Power Source - The DART 200 requires a nominal 13.8 V DC
regulated power source capable of supplying 2.5 amps maximum.
Refer to Appendix B, Product Specifications, for more details. Wire
the supplied power cord (Red positive, Black negative) with a Molex
connector to the power source using a 3.0 amp fuse
Refer to Figure 2-1 for instructions for installing the DART 200 with
the mounting bracket
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Figure 2-1. Installing DART 200 with mounting bracket
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Antenna considerations
The DART 200 uses standard mobile cellular radio signals and any
standard cellular antenna of good quality with a maximum gain of 3 dB
(FCC requirement) will function properly subject to the following
guidelines:
?
NOTE:
Snub-nosed (rubber
duck) antennas,
·
Location
although they may work
in some areas, are NOT
recommended.
Locate the antenna as far away from personnel as possible to
minimize signal blocking. For optimum reception, in fixed location
applications position the antenna above the height of personnel and
nearby equipment or structures. If used inside locate the antenna as
close to a window as possible. In mobile applications, locate the
antenna outside and away from or above any portion of the vehicle
body that can block the RF signals. To determine the actual signal
strength, attach a PC with an ASCII terminal emulator, such as
Procomm, or Kermit, to view the Receive Signal Strength Indication
(RSSI) value in S-Register 102.
Operating the unit
without an antenna
does not damage the
modem but can cause
unpredictable results.
·
Antenna cable
Select an antenna cable with a low loss, high quality, 50 ohm,
coaxial cable with the appropriate connectors. The cable can be any
length, but lengths greater than 12 feet increase cable loss and offset
the antenna’s nominal gain. If longer length cables are required, use
a heavier wire gauge to reduce the dB loss/ft and to minimize the
effect of the cable loss on antenna gain.
CAUTION:
For outdoor fixed
installations ground the
antenna cable using an
antenna discharge unit
to prevent damage to
the modem and the
attached equipment.
·
·
Ground plane
For installations where a good antenna ground plane (metal surface)
is not available, use a non-ground plane type of antenna to help
maximize signal reception
Proximity to other antennas
In general, do not locate the DART 200 and its antenna closer than
five feet to another antenna; in certain cases, even more separation is
required. In many vehicular applications, there are high-power
two-way voice transmitters used and usually the antenna mounting
locations are not five feet apart. The effect of the interference from
the two-way transmitters varies from slowing down response times
to blocking modem transmission.
In this situation, separate the antennas as far as possible and then do
a test with the voice system also being used. If the DART 200 works
satisfactorily you do not have an interference problem. If it does not
work properly, then use filtering on the two-way output, the DART
200 input, or both. The calculation to determine the required filtering
is not trivial and usually requires an RF engineer. However, if you do
not have the option to do a test first, this analytical approach is your
only option.
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DART 200 CDPD Modem User’s Guide
2 Installation and Setup
Troubleshooting
The DART 200 is thoroughly inspected during manufacturing. There are
no end-user access items within the case of the modem. If problems
occur, check the following:
?
NOTE:
To aid in
·
Power supply
troubleshooting use an
IBM-compatible PC
with an ASCII terminal
emulator, such as
Procomm, Terminal,
Kermit, Hyperterminal,
or a Mac with White
Knight.
If the Power On/Registration Indicator is not flashing or glowing
solid red, check the power source for adequate voltage. The modem
requires regulated 12 V DC at 2.5 A. If the power is marginal it can
be the problem. Check the fuse (if any) in the power source, and as a
final test use a voltmeter to check for an open cable.
The DART 200 draws up to 2.5 amps under maximum power output.
The power output is a function of the modem’s distance from the
Mobile Data Base Station (MDBS). It is possible for the modem to
work well with a particular power supply in a location requiring low
power output (low current draw), and yet to fail using the same
power supply in a location requiring a high power output. Check the
amperage rating of the power supply to verify that it is adequate for
all situations.
·
Channel acquisition
If the modem does not acquire a CDPD channel (fast blinking or
solid red light), refer to Channel acquisition, p. 2-10, for guidelines
on how to proceed.
·
·
Registration
If the modem does not register refer to Registration, p. 2-15, for
guidelines on how to proceed.
Unsuccessful data transfer
If the unit registered, but application data transfer is unsuccessful,
check that the RS-232 cable is properly attached. If that does not
correct the problem, substitute a good RS-232 cable (known to
work). If that does not work, you may have a flow control problem.
Refer to Flow control, p. 8-12, for guidelines. Also, review the Dial
command (ATD) in Appendix F, DART AT Command Set, Auto
Answer setup, p. 8-11, and Setup options, p. 5-17 or Basic UDP
setup options, p. 5-4, setup options as appropriate.
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2 Installation and Setup
Getting started
Before opening the DART 200 box, but preferably before it arrives,
check that the following equipment is available:
·
A 12.0 V DC regulated power source with 2.5 amp capability. You
can either provide your own, or order the power source as an option
with the DART 200
·
·
A standard cellular antenna of good quality with a maximum gain of
3 dB. Cable attached magnetic mount antennas are preferred because
the antenna can be positioned easily for optimum signal reception
A PC with a communications program capable of operating in ASCII
terminal emulation mode. For IBM PC-compatibles this can be
Procomm, Windows Terminal, Hyperterminal, Kermit or something
similar
This makes the PC function as a terminal attached to the modem and
permits the entering of AT commands required for both modem
setup and diagnostics. It is recommended that the program chosen is
capable of logging terminal communications activity to a file for
later analysis or printout in the event that technical support is
required
·
A PC communications cable with a male DB9 connector. If your PC
has a DB25 communications port, get a DB25 to DB9 adapter
(available from electronics stores)
Modem setup
To setup the DART 200:
1. Connect the antenna, PC, and power supply to the DART 200 using
appropriate cables and connectors. The red light on the end of the
modem turns on and start blinking at a rate of approximately once
per second (slow blink). If the light does not turn on, check the
power source and connections.
The red OPR light doubles as a signal strength indicator. When the
DART 200 finds a usable CDPD channel the rate of blinking
increases in proportion to the strength of the received signal. This is
discussed in more detail in Channel acquisition, p. 2-10.
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2. To proceed, your PC must have the ASCII terminal emulation
program installed and active, and be attached to the CDPD modem
by the PC communications cable. To verify the setup, enter AT and
press ENTER: an OK response should return. To verify that the
connection is with the DART 200 and not with an internal modem,
enter ATI1 and press ENTER. If the response is the modem software
version and date, proceed to Basic modem personalization. If you
fail to get that response, verify that your cable is working and that
the correct COM port is specified for the terminal emulation program
and repeat this step.
3. If you still fail to get the AT echo and/or the OK, enter an AT&V
command to display the modems communications setup, profile,
S-Registers and EID. The first three fields below the baud should be
E1, V1 and Q0. If the values are anything else, change to the correct
values and save the new values by entering ATE1V1Q0&W.
If the AT&V command fails, contact your DART 200 supplier for
technical assistance.
Basic modem personalization
The DART 200 requires an IP Address to be set internally before it can
be registered on the CDPD network. In addition, the side preference (A
or B) for your carrier needs to be specified. This information can be
preloaded by the carrier, but generally the carrier gives it to you upon
request. To determine if the IP Address was preloaded, refer to step 1
(below). If the IP Address was not preloaded contact your carrier to
obtain one along with the side preference (A or B), and a Domain Name
Server (DNS) IP Address.
In addition to the side preference, the DART 200 has 23 additional
operational parameters and several Status (S-)Registers to review. The
default values for these parameters and S-Registers can require changes
if they are not appropriate for your application. However, for initial setup
the default parameters (except for side preference) are adequate.
To set up the DART 200 for operation:
1. Load the IP Address supplied by the carrier. To check if it was
preloaded, use the AT\S? command, as shown in this example:
at\s?
* NEI 0 = IP ADDRESS 198.225.189.032 GMID 00000
OK
* - Means the Network Entity Identifier (NEI) is active
The DART 200 in the sample has the IP Addresses already entered.
Ignore the Group Multicast Identifier (GMID) field for now.
If your modem has no IP Address, the response to the AT\S?
command is OK. Enter the IP Address now, by:
·
Putting the modem into Service Provider mode with an
AT^P+51348954 command
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·
·
Entering the IP Address with an AT^An.n.n.n. It defaults to
being put into the first entry in the IP Address table (NEI 0). For
more information, refer to the AT^A command in Appendix F,
DART AT Command Set
Verify that the IP Address was entered correctly using AT\S?
2. Examine the Modem Operational Parameters (Modem Profile). To
view these parameters, the communication port status and settings,
and the DART 200’s S-Registers use the AT&V command, for
example:
at&v
DART 200
Communication Port Settings:
Auto Baud: 9600 Baud, 8 Data Bits, No Parity, 1 Stop Bit(s)
E1 V1 Q0 F1 X1 &C1 &D0 &E1 &S0
\F3 \J0 \M0 \N3 \O1 \Q2 \T1 *A0 *B0 *C1 *G1 *K0 *R0 *T0
Current active profile
(factory defaults)
S00:000 S01:001S02:043 S03:013 S04:010S05:008 S06:127S07:020 S08:250
S09:005 S10:080 S11:175 S12:050 S13:060 S14:074 S15:010 S16:050 S17:010
S18:010 S19:151 S20:000 S21:098 S22:016 S23:091 S24:140 S25:000 S26:003
S27:140 S28:140 S29:090 S30:010 S31:010 S32:005 S33:002 S34:001 S35:065
S36:041 S37:007 S38:003 S39:010 S40:090 S41:140 S42:080 S43:100 S44:023
S45:050 S46:005 S47:050 S48:050 S49:040 S50:020 S51:013 S52:026 S53:000
S54:000 S55:000 S56:000 S57:000 S58:058 S59:000 S60:001 S61:143 S62:000
S63:000 S64:022 S65:003 S66:002 S67:020 S68:020 S69:108 S70:010 S71:006
S72:005 S73:005 S74:006 S75:008 S76:240 S77:030 S78:000 S79:001 S80:250
S81:017 S82:002 S83:030 S84:000 S85:000 S86:120 S87:000 S88:020 S89:010
S90:008 S91:003 S92:000 S93:000 S94:000 S95:011 S96:000 S97:002 S98:090
S99:008
EID: 0020EB000B71
Most S-Registers are used by the DART control program. The
S-Registers of interest to the end-user are discussed in the following
sections.
3. Set Side Preference with AT\Nn. This command specifies which
service provider side (A or B) to search for a usable CDPD channel.
In each geographical area, there is a maximum of two service
providers (an A side carrier and a B side carrier). Your carrier sets up
this value or provides you with their preference. The default is \N3
(A side preferred), but is not appropriate for most end-users. If you
have an A side carrier, enter AT\N1; if the carrier is B side enter
AT\N2.
4. Verify that there are no channel restrictions in place. These
restrictions are controlled by the \Jn parameter. The default value is
\J0, no restrictions, and is the desired setting. If this parameter has a
non-zero value from prior use, set it to zero with AT\J0 before
proceeding.
5. Save your changes into permanent memory with the AT&W
command. Issue this command after making the above changes to
ensure that new values replace the default values.
6. Display the modem profile using the AT&V command to check that
your change to the \N parameter was successful.
The basic setup for your CDPD modem is now complete.
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Selecting CDPD 1.0 or 1.1 mode of operation
DART firmware Version 3.0.1 and above can operate in either CDPD 1.0
or 1.1 mode; prior firmware versions support only CDPD 1.0. The
firmware version can be determined by the ATI1 command.
The default is to operate in CDPD 1.1 mode, but in areas where CDPD
1.1 is not yet active, the operating mode can be changed to CDPD 1.0.
To set CDPD 1.0 mode, set S-Register 95 to 8 (default is 11) as follows:
1. Enter Service Provider mode with AT^P+51348954.
2. Set S-Register 95 for CDPD 1.0 mode with ATS95=8.
3. Save change with AT&W.
4. Restart to activate the change with AT-R.
To change back to CDPD 1.1 mode, repeat steps 1 to 4, but set
S-Register 95 to 11 instead of 8.
Initial testing
Setup verification
The first step to make the DART 200 operational is to verify the setup by
doing the following:
1. Use AT\S? to view and verify the IP Addresses, for example:
at\s?
* NEI 0 = IP ADDRESS 198.225.189.032 GMID 00000
OK
* Means the NEI is active
If you are just starting, there should be no problem here, because the
IP Address was just entered. However, if the address needs
correction, put the modem into Service Provider mode with an
AT^P+51348954 command, then enter the IP Address with an
AT^An.n.n.n.
The GMID is used with multicast operation, the value now should be
zero.
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2. If the NEI information is correct, use AT&V to verify the side
setting (\Nn) and channel restrictions (\Jn), for example:
ar&v
DART 200
Communication Port Settings:
Auto Baud: 9600 Baud, 8 Data Bits, No Parity, 1 Stop Bit(s)
E1 V1 Q0 F1 X1 &C1 &D0 &E1 &S0
\F3 \J0 \M0 \N3 \O0 \Q2 \T1 *A0 *B0 *C0 *G1 *K0 *R0 *T0
S00:000 S01:001 S02:043 S03:013 S04:010 S05:008 S06:127 S07:020 S08:250
S09:005 S10:080 S11:175 S12:050 S13:060 S14:074 S15:010 S16:050 S17:010
S18:010 S19:151 S20:000 S21:098 S22:016 S23:091 S24:140 S25:000 S26:003
S27:140 S28:140 S29:090 S30:010 S31:010 S32:005 S33:002 S34:001 S35:065
S36:041 S37:007 S38:003 S39:010 S40:090 S41:140 S42:080 S43:100 S44:023
S45:050 S46:005 S47:050 S48:050 S49:040 S50:020 S51:013 S52:026 S53:000
S54:000 S55:000 S56:000 S57:000 S58:058 S59:000 S60:001 S61:143 S62:000
S63:000 S64:022 S65:003 S66:002 S67:020 S68:020 S69:108 S70:010 S71:006
S72:005 S73:005 S74:006 S75:008 S76:240 S77:030 S78:000 S79:001 S80:250
S81:017 S82:002 S83:030 S84:000 S85:000 S86:120 S87:000 S88:020 S89:010
S90:008 S91:003 S92:000 S93:000 S94:000 S95:011 S96:000 S97:002 S98:090
S99:008
EID: 0020EB000B71
If this is the initial setup, the only parameter that changed from the
default value is the side preference specification (\N). Verify that it is
set to match your carrier before proceeding. Refer to Basic modem
personalization, p. 2-6, for details.
3. If the modem has been used previously, then some of the profile
parameters and S-Registers might be altered. Check that the profile is
correct before proceeding to step 4.
4. If you made changes, save the new configuration with the AT&W
command before continuing.
Register representation
The DART 200 keeps its status and control information in S-Registers.
Many of its functions are controlled by bits within a register, and are
displayed as a numerical value. Figure 2-2 shows the register notation
used.
?
NOTE:
The bits are numbered
in high to low order
from left to right that is
the reverse of some
notation systems in
Figure 2-2. S-Register bit positions
wide use.
S-Register
Bit Position
7
6
5
4
3
2
1
0
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The values associated with the bit positions are listed below.
Bit Position
Value
0
1
2
3
4
5
6
7
1
2
4
8
16
32
64
128
For example, if register bits 0,3, and 5 are on, the register value would be
1+8+32=41.
Channel acquisition
For the DART 200 to acquire a channel for operation it must have a good
antenna and an MDBS near enough to deliver a signal that is strong
enough to be received by the modem. CDPD systems are currently
defined as being either forced hopping or dedicated.
In a forced hopping (often called sniff-and-hop) system, an MDBS has
multiple channels (from 1 to 21, but usually 7) shared by voice calls or
CDPD. CDPD uses any available channel when it is not in use for voice.
If a voice call wants a channel already in use for CDPD, the MDBS notes
that occurrence (sniffs) and moves CDPD to another available channel
(hops).
The modem detects the fact that the current channel no longer supports
CDPD (loss of sync), and searches for an alternate CDPD channel using
the MDBS’s adjacent channel list. In such a system, CDPD operates in
the time between voice calls. During busy periods there is little time
available. Applications requiring quick response times are adversely
affected by the hopping.
In a dedicated system, each MDBS has one or possibly two channels
assigned for CDPD use only. In such a system, contention with voice
calls is not an issue and application response times are much more
predictable.
·
CDPD Version 1.0 Mode Operation
In the above system types, the channel acquisition process is:
1. The DART 200 powers up and immediately begins searching for
a CDPD channel to use. It searches sequentially, from the lowest
numbered channel to the highest, on the side (A or B) it is
configured to use, starting at a relatively strong signal level (-60
dBm).
2. Each time the DART finds an active channel, the modem checks
to determine if it is in use for voice or available for CDPD.
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3. If the channel is not available for CDPD use, the DART
continues searching, dropping the allowable signal level by 10
dB after each pass through all the cellular channels on the side it
is searching, until it finds a usable channel or reaches the
weakest allowable signal level (-110 dBm).
4. If an available CDPD channel was not found, the search starts
over again at -60 dBm and the modem repeats the spiral search
process indefinitely until an available CDPD channel is found.
5. When a CDPD channel is found the modem checks that the
block error rate (BLER) is acceptable.
6. If the BLER is adequate, the DART extracts the network
operating parameters (continuously being broadcast by the
MDBS) from the data stream, then stays on the channel as long
as possible awaiting commands from the Mobile Application
Subsystem (MAS); the attached device. If the BLER is not
acceptable the search continues.
7. While on the CDPD channel, the modem accepts operating
parameters (called XID parameters) broadcast by the base
station, including thresholds, threshold time limits, and adjacent
channel lists. The modem continually monitors its radio
environment and compares the current signal quality to the
thresholds and time limits; if any of the thresholds are exceeded
for longer than their permissible time limit, the modem must go
find a better channel. To speed up this search the modem makes
use of the adjacent channel lists picked up from the base station
along with the operating parameters.
This process allows a modem to stay on an acquired channel, until
the signal strength or BLER fails the threshold test. In a situation
where the M-ES is mobile, the modem can continue to use a channel
far from its original acquisition point (a phenomenon known as cell
dragging). In many cases this causes interference with voice
channels on intervening base stations. One of CDPD Version 1.1’s
main objectives is to avoid cell dragging.
·
CDPD Version 1.1 mode operation
In the system types already described the channel acquisition process
is:
1. The DART 200 powers up and immediately searches for a
CDPD channel to use. It searches sequentially, from the lowest
number channel to the highest, on the side (A or B) it is
configured to use recording the signal strength (RSSI) of every
active cellular channel encountered.
2. The DART then sorts the channels in descending order of
strength and evaluates them to find the best available (strongest
signal) CDPD channel (in a dedicated system many in the list are
voice only channels).
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3. If the CDPD channel’s BLER is acceptable, the DART acquires
the power product, current CDPD operating parameters, and
adjacent channel lists from the MDBS. If the channel BLER is
not satisfactory, the modem goes to the next best CDPD channel
in the list and repeats this step using the next best channel.
4. Once a channel is acquired, there is no guarantee that the modem
stays there very long. In a sniff-and-hop system it is forced to
continuously hop from one channel to another because voice
traffic has priority. Even in a dedicated system, if the modem is
mobile, it is forced to frequently change channels as it travels
from one cell coverage area to another.
5. The XID parameters broadcast by the base station, in addition to
the thresholds, threshold time limits, and adjacent channel lists
used with CDPD 1.0, include an evaluation frequency (scan
time), and a signal strength change (scan delta) value. As in
CDPD 1.0 mode, the modem continually monitors its radio
environment and compares the current BLER value to the XID
threshold and time limit; if the threshold is exceeded for longer
than the permissible time limit, the modem finds a better
channel. To speed up this search, the modem makes use of the
adjacent channel lists picked up from the base station along with
the operating parameters.
CDPD Version 1.1 requires that the DART periodically evaluates
alternative channels to ensure that it is still operating on the best
available channel. Also, CDPD Version 1.1 requires that if the DART
detects an RSSI changes of more than a predetermined amount, from the
initial acquisition value, it must check that it is still using the strongest
channel in the area. These features, scan time (usually 90 seconds), and
scan delta (usually +/- 8 dB), help to keep the M-ES on the best available
channel, and avoids the cell dragging phenomenon common to mobile
M-ESs operating in CDPD 1.0 mode.
Whenever the RSSI threshold or scan delta is exceeded, or the scan timer
expires the modem must locate a better channel if possible. To speed up
this search, the modem makes use of the adjacent channel lists picked up
from the base station along with the operating parameters.
Problem determination
There are three ways to determine if a channel was acquired:
·
By observing the OPR light (simplest way). At power on this light
flashes at the rate of about once per second. When the DART 200
acquires a channel the rate of flashing speeds up to at least twice per
second and flashes faster as the signal strength increases. A very
strong signal causes the light to glow steadily
·
By viewing S-Register 101 with the ATS101? command. A value of
1 indicates that a channel has been acquired
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·
By viewing the Network Status Register (S-Register 57) with the
AT&V command or the ATS57? command. This is the
recommended method, because viewing S-Register 57 shows other
useful information, as shown in Figure 2-3
Figure 2-3. Viewing the network S-Register (S57)
ATS57?
160
OK
A value of 128 (bit 7 on) or higher indicates that the modem acquired
a channel. If auto-registration at power on (AT\R4) is specified, then
the value is 160 (bits 5 and 7 on) or 161 (bit 0 also on) indicating that
it completed registration.
If the DART cannot acquire a channel, move the antenna to a better
location. To determine the best location for the antenna you need some
indication of received signal strength. This is given by the RSSI; one of
the radio resource values. View RSSI with the ATS102? or the AT&V+
command.
Figure 2-4 is a snapshot of the CDPD channel at a specific point in time.
View this data several times to see if the modem is staying on a single
channel (S-Register 100) or continues to search. If the value in
S-Register 101 is a zero, then the search is continuing.
Figure 2-4. Monitoring the CDPD channel
at&v+
DART 200
S100:00799 S101:00001 S102:-0073 S103:00002 S104:00040 S105:00000
S106:00001 S107:00000 S108:00022 S109:00010 S110:00079 S111:00001
S112:00000 S113:00000 S114:00000 S115:00000 S116:00000 S117:00000
S118:00018 S119:0FFFF S120:00000 S121:00002 S122:00000 S123:00002
S124:00030 S125:14400 S126:00005
If the modem cannot acquire a usable channel (S-Register 101 = 1) after
a few minutes there are several possible causes:
·
The signal strength is too weak
·
·
·
The cell is not currently CDPD capable (check with your cellular
carrier)
The modem has an incorrect channel restriction configuration. Use
the AT&V command to check the \Jn setting
The side setting is wrong. Use the AT&V command to check the
\Nn setting
·
·
There is an interference problem
The modem is faulty
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If the problem persists after checking the above possibilities, try power
cycling the modem. If that fails to help, contact your modem supplier for
assistance.
To determine if you have a channel restriction problem check the setting
of the \J parameter with an AT&V. If it is \J0 then the DART 200 has no
channel restrictions, so this can be eliminated as a possible source of the
problem. If \J has any other value then bypass the problem by entering
the AT\J0 command followed by an AT&W.
The S-Registers of interest in the AT&V+ output are summarized in
Table 2-1. The remainder of S-Registers are described in Appendix E,
S-Registers.
Table 2-1. S-Registers above 100
S100
S101
S102
S103
S104
S105
S106
S107
S108
S109
S110
S111
S112
S113
S114
The channel currently being reported (may not be acquired)
Will be 1 if a channel has been acquired
RSSI for the channel being reported
Output power (0 to 7 with 0 being highest and 7 lowest)
MDBS power product (a request for a specific power output)
Current BLER (receive block error rate - %)
Current SER (symbol error rate - %)
Current LSAI (CDPD V1.0), or WASI (CDPD V1.1)
Current SPNI (service provider network identifier)
Current CSI (channel stream identifier)
Current LCI (local cell identifier)
Current Area/Cell color code
Current TX BLER (transmit block error rate - %)
Current SIE (symbols in error)
Current SPI (Service Provider ID) (CDPD V1.1)
XID RSSI threshold, time (CDPD V1.0)
* threshold is dBw above -143 (in this case -125);
* time (in 1/10 sec) is how long RSSI can be below threshold before a
channel hop must be taken (5 seconds in this case)
Not Used (CDPD V1.1)
XID BLER threshold, time (CDPD V1.0)
* Block error rate threshold (1/n) in % (10% in this case)
* time (in 1/10 sec) is how long BLER can be above threshold before
a channel hop must be taken (1 second in this case)
Not Used (CDPD V1.1)
S115
S116
XID SER threshold, time (CDPD V1.0)
* Symbol error rate threshold (1/n) in % (10% in this case)
* time (in 1/10 sec) is how long RSSI can be below threshold before a
channel hop must be taken (5 seconds in this case)
Reserved
Reserved
~ ~ ~
S117
S118
~ ~ ~
S126
Registration progress counter
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2 Installation and Setup
If the modem stabilizes for short periods before restarting the search, the
AT&V+ output shown in Table 2-1 can be useful.
S-Register 102 contains the RSSI value in dBm. The less negative the
number the stronger the signal, for example, for CDPD 1.1:
·
Strong signals are in the range of -45 to -59
Good signals are in the range of -60 to -74
Acceptable signals are in the range of -75 to -89
Weak signals are in the range of -90 to -104
·
·
·
·
Signals below -100 are usually not dependable and can prevent the
modem from acquiring the channel
Sometimes local radio interference prevents channel acquisition. If the
BLER in S-Register 105 is above 10%, this could be the problem. Try
moving the antenna as far as possible from its current location or, if
possible, move to another location to determine if the problem can be
lessened.
Before deciding that the location is unsuitable, execute the AT&V
command and examine S-Register 60. If the 2 bit is on (usually a 5), then
the modem was set up to suppress channel searching, probably for use at
a trade show. Reset S-Register 60 to the default value of 1 with an
ATS60=1 command, and save it with an AT&W command. If this was
not the problem, contact your carrier to discuss the lack of CDPD
coverage.
Registration
Once the DART 200 acquires a channel the next step in the initial
operation process is registration; performed by the AT\R command.
The first few times you register the modem use manual registration
(AT\R1), to get a feel for timing, and from the timing an indication of
potential problems. When registration becomes routine use continuous
auto-registration (an AT\R4 command) combined with an ATS13=0
command. Save these changes with an AT&W command, and activate
the changes by power cycling or restarting (AT-R) the modem.
CAUTION:
With auto-registration
active the DART can
lock up, requiring a
power cycle to clear it,
if manual registration
(AT\R1) is attempted
and the registration
fails to complete
This setup causes the modem to attempt to register at power on and
whenever the modem loses registration, for example, when driving out of
coverage. Registration status can be viewed by using the ATS57?
command, as shown in Figure 2-5.
successfully.
Figure 2-5. Viewing registration status with ATS57?
ATS57?
161
OK
(bits 7, 5, and 1 are on)
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The bit definitions in Figure 2-5 are as follows:
·
·
·
Channel acquired indicator (bit 7)
Automatic registration switch (bit 5)
Registration indicator (bit 0)
An odd value in S-Register 57 indicates a registered modem.
If the DART has problems registering, begin problem determination by
checking the contents of S-Register 56 with the ATS56? command. The
possible return codes are listed below:
?
NOTE:
Most carriers and
equipment
manufacturers follow
these guidelines making
problem determination
easier. If these
guidelines are not
followed, more
ingenuity is required.
·
S-Register 56 Return Codes
Return codes 0 through 7 are suggested by the CDPD specification.
0
Reset condition - Also, registration is incomplete but did
not time out. Refer to the description of S-Register 126 in
the next bullet point for details
1
Registration denied - Usually means IP Address is being
used by another device. On some systems it could also be
an invalid NEI or a credentials mismatch
Service currently unavailable
Invalid NEI (IP Address)
Insufficient authentication credentials
2
3
4
5
6
7
Unsupported authentication credentials
NEI has exceeded usage limitations
Service denied on this subnetwork - service can be obtained
on an alternate Service Provider network
Timer expired waiting for the home MDIS Intermediate
System Confirmation (ISC) registration response - Usually
caused by router problems between the home and serving
MDISs
250
251
252
254
255
MDLP parameters unsupported
MDLP version unsupported
Could not access the CDPD network
Could not de-register because M-ES was not registered
·
S-Register 126 - Registration Progress Indicator
CDPD registration is a four-step process that can, if there are
problems anywhere in the system, be delayed or halted at any of the
steps. If your registration attempt is unsuccessful, use ATS126? to
view S-Register 126 to determine at what step in the registration
process progress halted.
0
1
Protocol not active
Waiting for Temporary Equipment Identifier (TEI) assignment
from MDIS
2
3
4
Link connection establishment pending - waiting for the
Unnumbered Acknowledgement (UA) from MDIS
Encryption key exchange pending - waiting for MDIS Key
Exchange (IKE) from MDIS
Registration pending - End System Hello (ESH) sent, waiting for
Intermediate System Confirmation (ISC) from MDIS
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5
NEI successfully registered
The descriptions of S-Registers 56 and 126 usually give a good idea
of what the problem is. The following section describes some of the
most common conditions leading to registration failures.
Troubleshooting registration failure
The most common conditions leading to registration failures and possible
solutions are listed in Table 2-2. If your problem does not appear in
Table 2-2, or if after checking the conditions you cannot find the
problem, contact your carrier for assistance. If your carrier cannot find
the problem, then contact the modem supplier for guidance
Table 2-2. Registration failure troubleshooting
Condition
Result
Code
Solution
Weak signal
strength
0 or 254
1. Verify that the RSSI is adequate. Refer
to Channel acquisition, p. 2- 10, for
instructions.
2. If you are mobile, the signal could be
temporarily out of range. If you are
stationary, you could be in a marginal
reception area. If you are stationary
and have a magnetic mount antenna,
relocate the antenna while observing
S-Register 102. The objective is to get
a less negative value.
3. If this does not improve the signal, or
if you are mobile use a better (higher
gain) antenna. Do not use an antenna
with gain greater than the FCC
allowed maximum of 3 dB.
Wrong side
specified
3 (invalid
NEI)
Check that you are operating on the same
side (channel range) as your carrier,
because if there are two CDPD carriers in
your area you may have acquired a channel
on the wrong system.
1. Use the AT&V command to view the
\Nn parameter, where n specifies
which side (1 = A side, 2 = B side)
you are operating on.
2. Correct the side setting, if necessary.
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Table 2-2. Registration failure troubleshooting (cont.)
Condition
Result
Code
Solution
Invalid IP
Address
3 or 1 (on
some
systems)
1. If the side setting is OK, verify that the
modem’s IP Address is correct, by
using the AT\S? command to view the
IP Address. If the modem has more
than one IP Address in the table,
verify that the active NEI, the one with
the asterisk (*) to the left, is correct.
This condition could also mean that
the carrier did not activate this IP
Address.
2. Contact the carrier to ensure that the
IP Address is valid and active
Expired IP
Address
6
As CDPD networks grow, some carriers
are concerned about unauthorized use of
unused IP Addresses to gain access to the
network. To minimize this likelihood an
expiration time is used, usually a few hours
long, on each new IP Address. If you are
slow in registering a modem with a
recently assigned IP Address, the
expiration time period can be exceeded.
Find out from your carrier if they employ
this strategy, and if so register new IP
Addresses promptly.
Authentication
(credentials)
problem
4 or 5
Each IP Address has two credential values
associated with it: a sequential number and
a random number. These numbers are
initially set to zero at the MDIS when the
IP Address is assigned to an end-user.
When the end-user puts the IP Address into
the modem these values are also set to
zero.
When the IP Address is registered, these
values are compared at the MDIS to ensure
that they match. If they do, a new random
number is generated at the MDIS and
returned to the modem, and both ends
update their sequential numbers. On each
subsequent registration these values are
compared by the MDIS (before updating)
to see that they match. The modem keeps
these credentials separately for each slot in
the NEI (IP Address) list.
Problems can arise if the IP Address is
reloaded after it was registered, or is being
reused or shared among modems. Any of
these activities will cause the modem
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Table 2-2. Registration failure troubleshooting (cont.)
Condition
Result
Code
Solution
Authentication
(credentials)
problem (cont.)
credentials to be reset. Trying to register a
modem after doing this will cause a
credentials error because the reset values in
the modem do not match the values the
MDIS has for that IP Address from prior
usage.
This problem is not likely when you are
initially registering a new modem, unless
the IP Address was previously used in your
organization. If a credentials problem is
indicated, contact the carrier to have the
credentials for the IP Address reset.
If you suspect that this occurred, use the
AT-Z command (in service provider
mode) to view the actual credentials. If the
displayed credentials are zero, call the
carrier to get the IP Address reset.
Flow control
problem
Not
applicable
This condition is only possible if you are
using manual registration (AT\R1) instead
of automatic registration. If, after you key
AT\R1 and press ENTER, the cursor returns
to the A of the AT and the modem does not
return an OK or an ERROR within the
time-out period (S-Register 13) you likely
have this problem.
Flow control is only applied when the
modem is in online mode or is interacting
with the network in command mode (as it
is when trying to register). Even if the flow
control is set improperly, or has a cable
problem that impacts flow control, you will
not notice it until you try to register. The
flow control setting defaults to hardware
flow control, indicated by \Q2 in the
modem profile, and this should match the
COM port setting on your PC’s terminal
emulator program. If the settings match try
changing them both to no flow control
(\Q0) on the DART. If registration now
works then a broken or missing pin, faulty
connection, or broken or missing RTS or
CTS wire is the likely source of the
problem.
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Table 2-2. Registration failure troubleshooting (cont.)
Condition
Result
Code
Solution
Power supply
problem
Not
applicable
The DART operates on a voltage of 11 to
16 VDC with a current rating of 2.5 amps.
Voltage level fluctuations caused by using
an unregulated power supply, or a supply
with too low a current rating will cause the
modem to experience a power reset. This
forces the modem to reset itself before it
can complete the multi-step registration
request.
The most frequent problem is too low a
current rating. The MDBS controls the
output power of the DART. The DART
may work well with a particular power
supply in a location where low power
output is required, and yet fail using the
same power supply in a different location
if the power output demands are higher.
Use a power supply with an amperage
rating of at least 2.5 amps to avoid this
problem.
MDIS or
network
problem
251, or 252 in Registration problems can be caused by the
S-Register 56 MDIS, or by the network beyond. If you
are operating in an area where CDPD
service is new or has recently had software
changes then this is a possibility.
OR
250 in
If your serving MDIS is different than your
S-Register 56 home MDIS (usually occurs if the F-ES is
in one carrier’s territory and the DART is
registered on a different carrier’s MDIS) a
network router or link problem could cause
the registration attempt to time out.
1. View S-Register 126 to determine how
far through the registration process the
modem had progressed. Home MDIS
delay problems show up as 4 in this
register.
2. Contact your local carrier for
assistance
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DART 200 CDPD Modem User’s Guide
2 Installation and Setup
Basic communications
The final step in the initial setup process is to confirm that the DART
200 can communicate with the network by performing a ping. The
DART 200 sends a fixed length character string to another device that is
registered on the network, and requests that it be echoed back. However,
to do a ping you need the address of another registered device.
Get two addresses to ping: a network server or Domain Name Server
(DNS), and a second DART adjacent to the first. Get the IP Address of a
network server or DNS from your carrier at the same time you get your
IP Address assigned. If you can ping the server or DNS, basic
connectivity is functional. If you can ping a device, such as a second
DART, on the other side of the MDIS, then network connectivity is
established.
Ping is executed by the AT*P command, as shown in this example:
at*p198.225.191.25
Press <ENTER> to stop
PING Host (198.225.191.25): 60 data bytes & 8 header bytes
68 bytes from 198.225.191.25: icmp_sn=0. time=1380. ms TSR=7631.250S
68 bytes from 198.225.191.25: icmp_sn=1. time=920. ms TSR=7632.280S
68 bytes from 198.225.191.25: icmp_sn=2. time=790. ms TSR=7633.180S
68 bytes from 198.225.191.25: icmp_sn=3. time=1340. ms TSR=7634.620S
68 bytes from 198.225.191.25: icmp_sn=4. time=1440. ms TSR=7639.660S
68 bytes from 198.225.191.25: icmp_sn=8. time=860. ms TSR=7636.180S
68 bytes from 198.225.191.25: icmp_sn=5. time=1450. ms TSR=7637.730S
68 bytes from 198.225.191.25: icmp_sn=6. time=900. ms TSR=7638.740S
68 bytes from 198.225.191.25: icmp_sn=7. time=820. ms TSR=7640.620S
----198.225.191.25 PING Statistics----
10 packets transmitted, 10 packets received, 0% packet loss
0 sequence errors round-trip (ms) min/avg/max = 790/1127/1450
The ping executes continuously until the <CR> key is pushed. The ping
command is covered in detail in Appendix F, DART AT Command Set.
If the network server and another device were successfully pinged, the
initial operation is complete and you are ready to begin application
testing.
The time since reset (TSR) field represents the time in seconds since the
modem was last reset (through an AT-R command or a power cycle).
Problems with the ping are usually seen as time-outs. Most devices
respond in less than 2 seconds using the default ping packet size. Both
packet size (60 bytes plus an 8 byte header) and the time-out period
(default is 10 seconds) are in S-Registers 71 and 70 and can be changed.
If you increase the size of the packet, consider increasing the time-out
period to allow for the longer transit time of the larger packet.
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If increasing the time-out period does not correct the time-out failures,
the problem could be that the other device is not registered, or that the
path to it is not operational. Check with those responsible for the other
device to see that it is operational and registered. Next, check S-Register
57 to see if you have a channel and are still registered. If you are, then
verify that the IP Address of the ping target is correct. If S-Register 57
status is fine and the IP Address is also fine, contact your carrier to check
for network connectivity between the local modem and remote device.
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Chapter
3
CDPD Security Features
Airlink security
The Cellular Digital Packet Data (CDPD) network is a public wireless
data communications service vulnerable to casual eavesdropping. To
minimize this possibility, a data encryption mechanism is provided for
all non-broadcast communications between the Mobile Data Intermediate
System (MDIS) and the Mobile End System (M-ES).
If activated by the carrier, encryption services are implemented by the
MDIS. At registration time the Data Access Radio Transmitter (DART)
200 is told, during session negotiation, whether or not encryption is
being used. The M-ES has no choice and follows the lead of the MDIS in
using or not using encryption
Authentication services
M-ES authentication is provided within the CDPD network to prevent
fraudulent use of the network. This mechanism is implemented by the
MDIS, as follows:
1. The MDIS validates the Authentication Data (credentials) presented
by the M-ES at registration time by comparing them against
information stored in the MDIS authentication table.
2. If the credentials are acceptable to the MDIS they are updated, stored
back into the MDIS authentication table, and also sent back to the
M-ES for use when it next registers. Registration is denied if the
M-ES presented credentials do not match those stored for its
Network Entity Identifier (NEI) by the MDIS.
When an IP Address is first authorized for use by the carrier, or an IP
Address is loaded into a modem, the associated credentials are set to
zero. On each subsequent registration the credentials are for the IP
Address are updated as described in steps 1 and 2 above.
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DART 200 CDPD Modem User’s Guide
3 CPDP Security Features
Modem security management
Two types of modem security are provided for the DART 200:
·
Personal Identification Number (PIN) - Protects against unauthorized
use of the CDPD network. A PIN can be required before the modem
can gain access to the CDPD network
·
Service Provider Key (SPK) - Protects against modem operating
parameters being altered. An SPK is mandatory before making
changes
The use of the PIN can be required by the service provider, although
currently none do. If not required by the carrier, you have the option of
requiring it, or leaving it disabled (this is the modem default). However,
the use of the SPK is mandatory and cannot be disabled.
The intent of the security management feature is to provide a layer of
control at the end-user level, in addition to CDPD network authentication
services, to aid in the prevention of unauthorized access to the network.
Table 3-1 summarizes the DART 200’s PIN management system. There
are four keys and six AT commands, three of which will only function
when in service provider mode, involved in the total process.
Table 3-1. Key types
Key
Description
PIN
Prevents unauthorized access to the CDPD network by
blocking commands that access the network, including the
registration command (AT\R) and the dial command (ATD).
To use these commands an authorized PIN and the AT*E
command are required. If the PIN is entered incorrectly three
times in a row it becomes BLOCKED. The default is PIN not
required.
PIN
The AT*U command temporarily enables the PIN when it
Unblocking becomes BLOCKED, allowing it to reset or change to a new
Key
value. BLOCKED status is permanently cleared by the AT^C
command, and PIN values are reset or changed by the AT\P
command. If the PIN unblocking key is entered incorrectly 10
times in a row, it also becomes BLOCKED. The BLOCK of
the PIN Unblocking Key is also cleared by the AT^C
command.
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3 CDPD Security Features
Table 3-1. Key types (cont.)
SPK Prevents unauthorized changes to the modems operating
parameters. These include selected S-Registers as well as
modem IP Addresses. In addition, the use of selected AT
commands, including several of the security management
commands, is also controlled by this key. This key is enabled
by the AT^P command. If entered incorrectly three times in a
row, it will become BLOCKED.
When the SPK is in the BLOCKED state, entering any SPK
through the AT^P command causes a 30-second delay before
the BLOCKED response is returned. This delay imposes a
barrier to computer-generated attempts at finding the Master
Key value by unauthorized users.
Master Key Temporarily enables the SPK when it becomes BLOCKED
allowing the BLOCKED status to be cleared. Temporary
unblocking is performed by the AT^P command, and the
BLOCKED status is permanently cleared by the AT^C
command. The Master Key cannot become BLOCKED.
AT
The AT commands used to implement the security
Commands management feature (*E, \P, ^F, *U, ^P, ^C) and the default
keys are described in detail in Appendix F, DART AT
Command Set.
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4
Broadcast and Multicast
Operation
Overview
Broadcast and multicast are Cellular Digital Packet Data (CDPD)
functions that support sending the same data to a large group of IP
Addresses with a single transmission to the CDPD network. This
capability is implemented through Mobile Data Intermediate System
(MDIS) software.
The facility was originally defined for Fixed End System (F-ES) (host) to
Mobile End System (M-ES) (terminal) transmissions. However, some
MDIS manufacturers have implemented multicast to also support M-ES
to M-ES transmissions. Protocol restrictions prevent broadcast or
multicast messages from being encrypted. Check with your carrier to
determine if these capabilities are offered before planning to use it as part
of your application.
Broadcast and multicast transmissions are point-to-multi-point and
provide a one-way connectionless service. The protocol used is User
Datagram Protocol (UDP) or another unacknowledged protocol that
operates over IP, for example, ICMP PING. The operational
considerations are:
1. Broadcast or multicast data packets will not be received by a DART
200 with an active telnet or Transmission Control Protocol (TCP)
PAD session.
2. If a User Datagram Protocol (UDP) PAD session is active the
broadcast and multicast messages will be interspersed with the
application data packets and must be separated by the application.
3. In the case of Serial Line Internet Protocol (SLIP), the disposition of
the broadcast and multicast messages is a function of the support
provided by the software stack and end-user applications (one must
be UDP) operating on the Mobile Application Subsystem (MAS). If
a UDP session is not active, the messages will be lost.
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DART 200 CDPD Modem User’s Guide
4 Broadcast and Multicast Operation
Broadcast
The Broadcast function is used on a geographic coverage basis. To
support this function the MDIS is set up with a Broadcast Network Entity
Identifier (NEI) that includes a list of the Mobile Data Base Stations
(MDBSs) in the desired broadcast area in its definition. There can be
multiple broadcast areas within the coverage area of a single MDIS. The
message is sent (by the F-ES or an M-ES) to a Broadcast NEI at the
MDIS that replicates the message, puts a special broadcast header on it,
and sends it to the cells indicated by the broadcast list.
Any Data Access Radio Transmitter (DART) wishing to receive
broadcast messages indicates its readiness by having specified the *B1
profile parameter and by being ready to receive UDP datagrams. The
latter can be accomplished by having the UDP Server function active or,
if in SLIP mode, by having a Winsock UDP application active, and by
being ready to process any incoming broadcast datagrams.
For most applications broadcast is not appropriate, because broadcast
messages are sent to all the CDPD modems in the covered geography. It
is more useful to be able to specify that messages only go to all, or a
subset of the IP Addresses associated with a specific customer; a
capability offered by multicast.
Multicast
Multicast is set up similarly to broadcast, except that the MDIS is set up
with a Multicast NEI and a list of the M-ESs that belong to that specific
group rather than a list of cells, as is done by the broadcast function. The
message to be multicast is sent (by the F-ES or an M-ES) to the Multicast
NEI at the MDIS, that replicates the message and sends individual
messages to the M-ESs indicated in its multicast group list.
An M-ES can be a member of any number of multicast groups, however
it can only be active in one at any given time. An M-ES wishing to
receive multicast messages indicates its readiness by registering a
Multicast NEI and by being ready to receive UDP datagrams. The latter
can be accomplished by having the UDP Server function active, or if in
SLIP mode, by having a UDP application ready. In all of the preceding
cases the MAS is assumed to be ready to process any incoming multicast
datagrams.
Contact your service provider for information on the availability and use
of multicast service in your area.
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4 Broadcast and Multicast Operation
Multicast setup
For multicast set up the DART 200 with a multicast IP Address and an
associated Group Multicast Identifier (GMID), in addition to the normal
IP Address, as follows:
1. Enter the Multicast NEI (like any other IP Address) by using the
AT^A command.
2. Select the NEI for multicast use with the AT\S+n command, where
n is the slot number in the DART 200’s IP Address list.
3. Define the GMID, use the AT^G command that assigns a multicast
group ID to the slot containing the Multicast NEI, for example:
·
·
·
·
AT^P+51348954
AT^A198.225.189.35/1 Enter multicast IP Address in slot 1
AT^G12/1
AT\S+1
Must be in Service Provider mode
Set GMID for slot 1 to 12
Select IP Address in slot 1 for
multicast use
4. Verify the set up of your Multicast NEI with an AT\S? command; it
shows the CDPD modem’s NEI status. The screen appears as shown
in Figure 4-1:
Figure 4-1. Checking NEI status with AT\S?
AT\S?
SLIP = IP ADDRESS 001.001.001.002
MAS = IP ADDRESS 198.225.189.031
* NEI 0 = IP ADDRESS 198.225.189.031 GMID 0000C
+ NEI 1 = IP ADRESS 198.225.189.035 GMID 00012
SPI 0 = 00012
SPNI 0 = 00035
WASI 0 = 00001
OK
* - Indicates which slot contains the active point-to-point NEI (IP Address)
+ - Indicates the multicast NEI selected.
Both NEIs must be registered concurrently; there is no command to
register a multicast NEI by itself. Define and select the multicast NEI
before registering the point-to-point NEI. The GMID field in Figure
4-1 is only applicable to the multicast NEIs.
The DART 200 can have multiple Multicast NEIs defined, but can only
have one active at a time. The multicast designation for a particular slot
in the NEI table can be deactivated by an AT\S-n command, (where n is
the slot number), and a different one activated by an AT\S+n command.
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4 Broadcast and Multicast Operation
Some software stacks, used when the DART 200 operates in Serial Line
Internet Protocol (SLIP) mode, only receive broadcast messages
(including multicast) on a specific IP destination address, specifically the
point-to-point NEI. To provide for this limitation, the DART 200 permits
specifying whether or not the received destination IP Address (multicast
address) is replaced with the active point-to-point NEI before the
received packet is passed across the SLIP interface to the software stack.
This feature is implemented by using the AT*G command. AT*G1
(default) causes the received destination address to be replaced as
described above. AT*G0 passes the received packet across the SLIP
interface to the TCP stack unmodified, with the destination address being
that of the Multicast NEI.
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5
DART Supported Protocols
UDP
User Datagram Protocol (UDP) is the most basic transmission protocol
provided by the Data Access Radio Transceiver (DART) 200. It is a thin
protocol, adding only a port specification to the underlying Internet
Protocol (IP). It has the same features as IP, that is a best effort,
connectionless delivery service with the chief benefit being minimum
overhead.
UDP is not considered reliable because packet delivery is not guaranteed.
Packets can be lost, duplicated, delayed, or delivered out of sequence.
These conditions are not detected, and the sender or receiver is not
informed.
UDP is connectionless because sender and receiver are never logically
connected. If the intended receiver is not active the message is lost. It is a
best effort delivery, because the IP software makes an earnest attempt to
deliver the packets, failing only if system resources are overloaded or the
underlying networks fail.
Application programs using UDP must accept full responsibility for
handling the problems of reliability, including message loss, duplication,
delay, out-of-order delivery, and loss of connectivity.
These problems are often treated casually be programmers. Testing done
when using highly reliable, low delay local networks may not expose
potential failures. This explains why many applications that use UDP
work well in a local environment but often fail in dramatic ways on a
more global network.
Despite these warnings, UDP is still the most efficient and widely used
protocol. Take care in analyzing the application being implemented, the
network being used, and the Mobile Application Subsystem (MAS)
device involved to determine if an application implementation using
UDP is feasible.
·
How likely is it that the network being used can cause these
problems?
Small, non-Internet networks are not likely to cause problems.
·
How much compute power and programming capability does the
MAS device have?
Lack of available memory or programming capability can preclude
adding the needed reliability features into the application.
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5 DART Supported Protocols
While UDP offers the possibility of using fewer data packets and less
total bytes to implement an application than TCP, adding the features
already described can consume some of these savings, and requires a
major programming effort.
The DART 200 provides basic UDP, available since the DART was first
commercially available, and the UDP server, which become available
with firmware version 3.0.4 for the DART in April, 1996. These are
described separately in the following subsections to delineate the setup
options and functions available with each.
Basic UDP characteristics
Basic UDP was originally offered on the DART 100 and early versions
of the DART 200. It provides a simple UDP communications capability
characterized by no server (auto answer) capability, and the need for both
sides of the communications session to use a common port number.
Without server capability the DART 200 issues a UDP dial (ATDP)
command to get into an online state so that it can receive incoming
datagrams.
Basic UDP communication
Before initiating UDP communication register the DART 200 on the
Cellular Digital Packet Data (CDPD) system. Refer to Channel
acquisition, p. 2-10, and Registration, p. 2-15, for instructions on
registering the DART 200.
To initiate UDP communication:
1. Basic UDP has no auto answer capability, so the modem must be in
online mode before communications can be started. Use the ATD
command with the P (for UDP) modifier followed by the IP Address
and port number of the destination system (host or another MC-
DART) to put the DART 200 into online mode. If the DART will be
used by a remote device that cannot issue a UDP dial command, then
basic UDP is not a viable option; the UDP server option must be
used.
2. If no port is specified the default port number (23) is used. Since the
DART listens by default if another DART is the target. If a port
number is required, specify it now. Unless the application operates
on a closed system, port numbers should be in the range between
1025 to 4999 to comply with industry standards.
?
NOTE:
The DART
implementation of basic
UDP requires that both
the host and MAS dial
commands use the same
port number.
Alternatively, the dial could reference an IP Address/port stored in
the DART 200 dial list by the ATDPSn command: where n is the
number of the desired IP Address in the dial list. Refer to Modem
dial directory, p. 8-24, or the &Z command in Appendix F, DART
AT Command Set, for more information.
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Even though a successful ATDP command receives a CONNECT
response a connection was not established. The ATDP merely passes
the IP Address and port number of the destination system to the
DART 200, where they are stored for use in constructing UDP
headers for the data packets that follow. If the communication
session is being set up between two DARTs, both have to execute a
UDP dial command to go into online mode so that communications
can begin.
?
NOTE:
Even though a
successful ATDP
command receives a
CONNECT response a
connection was not
established.
If data transmission is initiated by the MAS:
1. The MAS writes application data blocks to the DART 200.
2. Data blocks are assembled until a data forwarding condition, as
described in Data forwarding, p. 8-8, occurs.
3. The DART 200 attaches the UDP header and checksum and sends
the packet to the network.
4. The datagram (packet) is directed by the network routers to the
appropriate port on the designated host. If the host or host port is
inactive the data is lost and the local application is not informed.
Good UDP application design includes packet sequence checking, and
acknowledgments to ensure that both the sender and receiver can
determine if all application data arrived successfully.
If the MAS is on the receiving end:
1. When expecting a message following the initial CONNECT message
or in response to an output message, the MAS reads continuously
until all expected data is received.
2. When the data block is received it should be checked against
preceding blocks for sequence errors before proceeding.
3. The DART 200 passes the data portion of the incoming datagram on
to the MAS after removing the source IP Address and port number
from the header for use as the destination address in the response (if
required). This address data is available to the MAS through
S-Register 53 with an ATS53? command; it cannot be viewed with
an AT&V.
?
NOTE:
A good error-checking
and acknowledgment
scheme is essential to
successful UDP
operation.
The handling of network connectivity issues (such as loss of carrier), as
well as data delivery and sequencing, is the responsibility of the MAS.
Refer to Modes of operation, p. 8-3, for guidelines on handling network
errors.
Session termination may or may not be necessary. If the MAS originates
sessions, it must terminate the first session before starting a second.
Terminate sessions by the escape function followed by a hang-up
command (H), as described in Appendix F, DART AT Command Set. If
the MAS only receives calls (performs a server function), it can remain
in online mode waiting for a datagram (service request) from another
client.
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5 DART Supported Protocols
Because UDP is a connectionless protocol, a single M-ES can
communicate with multiple M-ESs at the same time as long as timing
considerations are closely followed.
When a DART 200 receives a datagram from another M-ES:
1. The DART 200 removes the source address information (IP Address
and port number) and saves it to use as the destination address for its
response message.
2. After the DART 200 responds to client #1, it is free to receive and
respond to requests from client #2, #3, and so on. The requests and
responses from clients can be interspersed, as long as no request
comes in from a client before a response is given to the previous
client. If that occurred, the response intended for #1 would go to #2,
followed by the normal response to #2.
Unless the timing of requests can be scheduled or controlled to prevent
this from happening, avoid this type of operation with basic UDP. The
UDP server is designed to handle this, as described in UDP server, p.
5-5.
?
The DART 200 with UDP server capability uses a bit in Status
(S)-Register 82 to enable and disable basic UDP operation; basic UDP
operation is enabled. If you do not have an older DART compatibility
requirement, it is strongly recommended that basic UDP not be used.
Refer to the bullet point on backward compatibility on p. 5-7, for
information on enabling and disabling the basic UDP mode of operation.
NOTE:
The DART default is
basic UDP active. It is
strongly recommended
that this feature be
disabled so that the
UDP server function
will be active.
Basic UDP setup options
The following items must be set so the DART 200 can operate on the
CDPD network:
·
IP Address (^A)
·
·
Side Preference (\N in the modem profile)
Channel restrictions ( \J in the modem profile)
Refer to Basic modem personalization, p. 2-6, for a review of using the
AT commands, ^A, \N, and \J.
In addition, the following items are required for basic UDP operation:
·
·
·
Automatic registration - as described in Automatic registration,
p. 8-6
PAD mode - \O0 in the profile. Refer to \O command in Appendix F,
DART AT Command Set for details on using this command.
S-Register 82 set to 2 (default). Refer to the bullet point on backward
compatibility, p. 5-7, for details on setting this S-Register
Many of the following profile parameters may apply and need to be
evaluated. Some need to be set to provide the proper application
operating environment, others can be allowed to default.
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5 DART Supported Protocols
To set up the options, first, review Chapter 8, Application Programming,
and the command descriptions in Appendix F, DART AT Command Set
before setting the following parameters, then proceed to step 1.
·
Command mode echo (En)
Data set ready (DSR) operation (&Sn)
Verbose Mode (Vn)
Data Forwarding operation (\Fn)
Quiet mode (Qn)
Manual transmit control (\Mn)
Online mode echo (Fn)
Flow control (\Qn)
Extended result codes (Xn)
Automatic transmit control (\Tn)
Data carrier detect (DCD) operation (&Cn)
Reception of IP broadcasts (*Bn)
Data terminal ready (DTR) operation (&Dn)
Listening Port (*Ln)
·
·
·
·
·
·
·
·
·
·
·
·
·
·
Escape code recognition (&En)
1. Set the key parameter, PAD operating mode (\On), to \O0 for UDP
operation. The default value is \O1, so it must be changed.
2. UDP is the only CDPD protocol that can receive broadcast messages.
Use the AT*Bn command to allow (B1) or to suppress (B0)
reception of broadcast traffic.
?
NOTE:
At present no carrier is
offering a broadcast
capability.
3. Check with your carrier to determine if multicast is available in your
area before proceeding to step 4.
4. Direct multicast messages to the modem’s listening port (refer to *L
command in Appendix F, DART AT Command Set). Multicast
messages can appear at any time; possibly interspersed with the
application data. The end-user’s application must handle the
multicast messages interspersed with the application data. For
applications with the modem set up to use multicast, be aware that it
cannot be suppressed by AT commands.
?
NOTE:
UDP is also the only
protocol that can
receive multicast
messages.
UDP server characteristics
The DART UDP server is a backward compatible extension to the
DART 200 basic UDP implementation with the following additional
features:
·
Auto-answer capability to permit Remote Terminal Units (RTUs)
with limited capability to use UDP. The RTU is not required to issue
a UDP dial (ATDP) command in order to receive messages when the
UDP server is active
·
Friends Only mode to restrict communications to a specific list
(maximum of 10) of source addresses (IP Address only). This helps
prevent unauthorized access to the MAS application
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·
Receive locking capability to allow the DART 200 to function as a
UDP server by holding off incoming messages until the preceding
message is answered
·
·
Eliminates the need for the M-ES and Host modems to use a
common port number. The server uses the source address contained
in the incoming packet as the destination address for outgoing packet
Backward compatibility with the basic UDP function in earlier
DART modems by an S-Register setting. When there are DART
modems involved in the UDP application that use non-server
software, activate this feature
These added features make the DART UDP server compatible with
industry standard client-server models where the client originates
communications and the server waits for incoming communications
requests.
UDP server setup options
In addition to the new options discussed here, the same setup options
used with basic UDP, as described on p. 5-4, also must be considered
before proceeding to step 1.
1. Set the defining setup parameter for the UDP server function ( *An -
select server type) to 2 with an AT*A2 command. Selecting this
option enables the UDP server function. The default value for this
parameter is *A0 (no server active). This is appropriate if the MAS
application always operates in client mode; always originates the
connection request with an ATDP command.
2. With the UDP server option enabled, choose the method used to
answer incoming calls. The preferred method is to set S-Register 0 =
1 with an ATS0=1 command, which puts the modem into permanent
auto answer mode. The alternative is for the MAS to use the answer
command, ATA. This command could be used in response to a
RING message, or in anticipation of an incoming call. However, in
the latter case, since the command is only active for 20 seconds it has
to be used in a programming loop to receive a call.
3. (Optional) Select the port to listen for incoming messages on. For
basic UDP the listening port is fixed at 2100. However, with the
UDP server the listening port can be set using the *L command. The
command format is AT*Ln where n is the desired listening port; a
decimal number in the range of 1025 to 4999 for compliance with
industry standards.
?
NOTE:
When the listening port
is changed it is not
active until the server is
stopped and restarted,
or the modem is reset
with an AT-R or a
power cycle.
4. If the listening port is changed, save it with an AT&W. The default
value for the listening port is still 2100 for backward compatibility
with basic UDP.
The remaining setup options for the UDP server are controlled by the
contents of S-Register 82, including:
·
Friends Only mode
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·
Receive locking
·
Backwards compatibility
The details of these options follow.
·
Friends Only Mode - Restricts communication with the modem (for
security reasons) to a predefined group of addresses (friends)
This feature is controlled by S-Register 82 which enables and
disables the comparison of datagram source addresses against a list
stored in the DART 200’s destination dial directory. Refer to the
AT&Z command in Modem dial directory, p. 8-24, or Appendix F,
DART AT Command Set for details. Only the IP Address portion of
the addresses in the dial directory is used with this feature. Bit 0 of
S-Register 82 controls this mode. The default is to accept all
incoming datagrams (bit 0 = 0).
This bit is significant only when the UDP connection is established
passively (server mode). When the connection is established actively
(by an ATDP command), incoming datagrams are accepted from the
destination address specified in the dial command regardless of the
address being in the friends list; this is consistent with basic UDP
operation.
In both of the above cases, the source address (IP Address and port
number) of the last accepted datagram is saved in a temporary
variable for use as the current destination address for all datagrams
being sent by the MAS during the current session. This source
address information is also saved in S-Register 53 where it can be
obtained with an ATS53? command. However, if the application
design allows the M-ES to receive messages from multiple clients,
outbound datagrams can only be sent to the last source of input data.
If this is a potential problem due to timing considerations, refer to the
next bullet point on receive locking.
·
Receive Locking - A UDP server feature that allows time for the
MAS to respond to a datagram without concern that another
datagram from a different source will overlay the current destination
address
This feature is controlled by bit 2 of S-Register 82. The default is
receive locking disabled (bit 2 = 0). The lock time out period is
specified in S-Register 83 in tenths of seconds (default is 3 seconds).
If receive locking is enabled, all datagrams arriving after the first
one, regardless of their source address, are held in a First-In-First-
Out (FIFO) queue until a data transmission occurs, or the time out
period expires, releasing the first datagram in the queue.
·
Backward Compatibility - Permits the UDP server to operate in a
mode compatible with the basic UDP provided in earlier versions of
the software (prior to version 2.0)
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This feature is controlled by bit 1 of S-Register 82. The default is
backward compatibility enabled (bit 1 = 1). When this bit is on the
UDP server does not generate a random port number as the source
port when the MAS issues an ATDP, but instead uses the port
number specified in the destination address of the dial command. In
backward compatibility client mode, the destination port cannot be
the same as the modem’s listening port if the UDP server is active.
?
NOTE:
This bit should be set to
0 if there are no DARTs
using basic UDP
participating in the
·
UDP server communication - UDP communications with the UDP
server active are similar to those for basic UDP, with the exception
of the call establishment operation discussed in Basic UDP
communication, p. 5-2. A discussion of call establishment operation
with the UDP server active follows.
network.
?
NOTE:
In active operation (client mode):
The UDP server is
compliant with industry
standard client-server
models where client
systems originate calls
and server systems
answer calls. Another
aspect of these
1. The MAS (or DTE) issues an ATDP command using the dial
string (ATDPn.n.n.n/x) or the dial list entry (ATDPSn) form to
put the M-ES into online mode. If no destination port is
specified the port number defaults to the standard telnet port
(23); this should be avoided.
2. Unless the application operates on a closed system, use port
numbers in the range of 1025 to 4999 to comply with industry
standards. The modem’s protocol stack generates a random
number for use as the source port for active mode sessions.
However, if the backward compatibility option is active the
source port number is forced to be the same as the destination
port address specified in the dial string.
standards is the
distinction between
active (client) and
passive (server)
operation.
As is the case with basic UDP, the CONNECT message received
when going into online mode does not imply that a logical
connection was established as it does with TCP. Instead, it
indicates to the MAS that the modem is in online mode, ready to
communicate, and that the destination address is saved for use in
constructing packet headers for data that follows.
3. In addition to putting the modem into online mode, the ATDP
generates a random port number for use in the packet source
address, which is also used as the active session listening port.
4. If the modem functions only as a client (*A0), the listening port
defined by the *L command is not active. The modem receives
datagrams on the active session listening port instead, and only
from the destination address (IP Address and port) specified in
the dial command.
If the modem functions in a dual role, both as client and server
(*A2), there are some additional items to be aware of, including:
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·
·
The modem’s server listening port is disabled for the
duration of any active client session. Incoming datagrams are
received on the active session listening port and only from
the destination address specified on the dial command until
an escape is performed and an ATH is issued; reactivating
the server’s normal listening port
If operating in backward compatibility mode, the destination
port number on the ATDP command must be different from
the modem’s server listening port
5. Following receipt of the connect message, application data
written to the DART 200 through the RS-232 port using device
specific commands.
6. This data is assembled until a data forwarding condition, as
described on p. 8-8, occurs.
7. The DART 200 then attaches the UDP header and sends the
datagram onto the network.
8. The datagram is directed by the network routers to the
appropriate port on the designated server. If the server is not
active when the datagram arrives it is lost, and the client is not
informed.
In passive operation (server mode):
?
1. The UDP server listens on the configured port (2100 or *L
specified) for an incoming datagram, then determines if the
datagram is to be passed to the MAS and the M-ES put into
online mode.
NOTE:
How the UDP behaves
is dependent on the
auto answer mode in
use.
2. With auto answer disabled when a datagram is received by the
UDP server, it first validates the source address (if the Friends
Only option is specified), and if it is acceptable issues a RING
result code. Refer for Auto Answer setup, p. 8-11, for more
details.
3. If an ATA command is not currently active, or is not issued
within 60 seconds, the arriving datagram is discarded and the
source address of the arriving datagram is not saved. No
indication of this event is presented to the MAS. If the ATA
command is, or becomes, active within the time-out period:
·
·
·
·
A CONNECT result code is issued
The modem enters online mode
The source address is saved
The datagram is passed to the MAS
4. With auto answer enabled, as described in Auto Answer setup,
p. 4-11, when a UDP datagram is received by the UDP server,
the modem first validates the source address (if the friends only
option was specified).
5. If the source address is acceptable then a CONNECT result code
is issued.
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·
·
·
The modem enters the online mode
The source address is saved
The datagram is passed to the MAS
In the answering modes already discussed:
1. The modem accepts incoming UDP datagrams.
2. The modem strips off the UDP header, and passes the packets
on to the attached device for processing.
3. Responses are assembled and transmitted as described in steps 1
and 2 for UDP clients.
4. The modem continues in this mode, accepting and transmitting
data until the MAS explicitly moves the modem to command
mode by issuing an escape sequence (+++), or by dropping DTR
with a non-zero &D option specified.
5. Now, the MAS can return to online mode with the ATO
command, or drop out of the CONNECTED state with the ATH
command. Issuing a hang up command (ATHn) causes the
current source (S-Register 53) and destination address to be
reset, and the UDP server to automatically listen for the next
datagram. At this point, both passive and active connection
requests will be honored.
A MAS functioning as a server receives calls from any client device.
However, it can only save one source address, the one that was
extracted from the last datagram received, for sending any required
response. For this reason, if multiple clients are expected server
modems must use receive locking to delay accepting subsequent
datagrams until a response is sent to the source of the prior datagram.
Datagrams subsequent to the first are placed in a FIFO queue for
later processing.
?
NOTE:
The DART 200 has
approximately 6K of
buffer space available
for storing queued
datagrams.
In both client or server modes, the modem extracts the source
address (IP Address and port number) from the first packet received
and stores it in S-Register 53. This information can be retrieved by
the end-user application, if needed, with an ATS53?, for example:
ats54?
198.225.189.21,4000
This address data cannot be viewed with the AT&V command. The
data remains in S-Register 53 until the session is ended by an ATH
command (client mode), or a datagram is received from a different
source (server mode).
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Sample UDP server setups
These settings give a general sense of the AT commands required to set
up a DART 200 for a UDP application. All relevant AT commands are
listed, including the defaults. All devices function differently, so the
setups that follow are general. These setups show specific items to
examine, but it is good practice to examine all of the setup values.
Two UDP setup examples are given:
·
Remote UDP setup - A remote telemetry application and a central
client application, that shows the setup for a server modem at an
RTU being polled by a host computer
·
Host UDP setup - shows the setup for a client modem at the host
computer that does the polling. This modem at the host arrangement
is suitable for bench-testing and limited use pilot implementations.
Production systems normally are direct connected through a leased
line or frame relay to a router at the customer’s host system (F-ES)
Remote UDP setup
The remote modem is set up as a server at the remote telemetry unit
where it responds to polls from a host computer. The sample RTU does
not use flow control and the data being sent is binary, not character, data.
This requires the UDP server to be set up with auto answer to respond to
polling, no flow control, and timed data forwarding because of the binary
data.
In Table 5-1, line items marked with an R (required) or an O (optional)
were changed from the default (D). After the changes are made save
them with an AT&W.
Table 5-1. Remote UDP setup
AT Command
AT^Annn.nnn.nnn.nnn
AT\N[1,2]
Req Opt Def Description
Input IP Address (if not already done)
R
R
D
Side Preference (get from carrier)
Use default - No channel access
restrictions
AT\J0
AT\R4
ATS13=0
Auto Registration at Power On
With AT\R4 sets Continuous
Automatic Registration
PAD mode required for UDP.
Set UDP Server mode
Use default - Listen on port 2100
Activate auto answer for server
Turn off backward compatibility.
Consider friends only mode if
unauthorized access is a concern.
R
R
AT\O0
AT*A2
AT*L2100
ATS0=1
ATS82=0
R
R
D
O
R
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Table 5-1. Remote UDP setup (cont.)
AT Command
ATE0
ATV0
Req Opt Def Description
No command mode character echo
Use terse result codes
Use default - Result codes are sent to
the RTU
O
O
D
ATQ0
ATF1
D
Use default - Do not echo transmitted
data to the RTU
ATX1
AT&C1
D
D
Use default - Extended result codes
Use default - DCD follows state of
the connection
AT&D0
D
Use default - You may want to
consider using DTR to escape if RTU
supports it
AT&E2
AT&S0
AT\F3
Filter escape sequence from output
Use default - DSR is always active
Use default - Applies only if \M1
specified
Use default - Do not recognize data
forwarding characters
O
D
D
AT\M0
D
AT\Q0
AT\T1
Most RTUs do not use flow control
Timed data forwarding - Always use
with binary data
Use default - Many CDPD Carriers
have not implemented Broadcast.
Use default - Does not apply to UDP
Use default - Does not apply to UDP
Use default - Does not apply to UDP
Use default - Does not apply to UDP
Use default - Does not apply to UDP
O
D
AT*B0
D
AT*C1
AT*G1
AT*K0
AT*R0
AT*T0
D
D
D
D
D
Host UDP setup
The host (client) modem is set up to support polling of remote devices by
the host computer. The specific host uses flow control and the data being
sent is binary, not character, data. The polling function does not require
the UDP server, but requires flow control, and timed data forwarding
because of the binary data.
Use this setup only for bench testing or a limited use trial. A production
application uses a leased line, frame relay, or Internet connection
between the host and the MDIS instead of a modem. In the latter
scenario, the production host application needs to interface with a
software stack (replacing the modem stack to operate with the CDPD
network).
In Table 5-2, only the line items marked with an R or an O are changed
from the default (D). After making changes, save them with an AT&W.
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Table 5-2. Host UDP setup
AT Command
AT^Annn.nnn.nnn.nnn
AT\N[1,2]
Req Opt Def Description
Input IP Address (if not already done)
Side Preference - (get from carrier)
Use default - No channel access
restrictions
R
R
D
AT\J0
AT\R4
ATS13=0
Auto Registration at Power On
With AT\R4 sets Continuous
Automatic Registration
R
R
AT\O0
AT*A0
PAD mode required for UDP.
Use default - No server function
required
R
D
AT*L2100
ATS82=0
ATE0
ATV0
ATQ0
D
R
O
O
D
Use default - Listen on port 2100
Turn off backward compatibility.
No command mode character echo
Use terse result codes
Use default - Result codes are sent to
the host
Use default - Do not echo transmitted
data to the host
Use default - Extended result codes
Use default - DCD follows state of
the connection
Use default - You may want to
consider using DTR to escape
Filter escape sequence from output
Use default - DSR is always active
Use default - Applies only if \M1
specified
ATF1
D
ATX1
AT&C1
D
D
AT&D0
D
AT&E2
AT&S0
AT\F3
O
D
D
AT\M0
AT\Q2
AT\T1
AT*B0
D
D
D
D
Use default - Do not recognize data
forwarding characters
Use default - Most PC’s use flow
control
Timed data forwarding - Always use
with binary data
Use default - Many CDPD Carriers
have not implemented Broadcast.
Use default - Does not apply to UDP
Use default - Does not apply to UDP
Use default - Does not apply to UDP
Use default - Does not apply to UDP
Use default - Does not apply to UDP
AT*C1
AT*G1
AT*K0
AT*R0
AT*T0
D
D
D
D
D
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TCP
Transmission Control Protocol (TCP) is an advanced transmission
protocol that adds substantial functionality to the underlying Internet
Protocol it is built on. Because of this structure it is often referred to as
TCP/IP. The advantage of TCP is reliability of data transmission;
achieved by using positive acknowledgments with retransmission if
required. The main disadvantage is the overhead needed to provide this
reliability under any and all conditions.
Unlike UDP, TCP offers both reliable and connected data transmission
service. Lost, delayed, duplicated, or out of sequence packets are
detected and automatically corrected. A logical point-to-point connection
is established and maintained throughout the communications session.
TCP is ideally suited for applications where speed of development is
critical, or for applications where the MAS is low on compute power,
available memory, or both. It requires very little other than session
establishment, sending data over the serial port, and session termination
to get a basic application operational.
The price for this reliability is the number of extra data packets used and
the time required to process them. Both need to be considered when
selecting an application protocol.
DART TCP capabilities
The DART software stack offers industry standard client-server
capability where the client originates communications and the server
waits for incoming requests. In server mode it includes auto answer
capability and an optional Friends Only mode. Friends Only mode
restricts the devices the server can receive calls from to help prevent
unauthorized access to applications or devices.
Friends Only mode operation
Friends Only mode permits communication with the modem to be
restricted (for security reasons) to a predefined group of addresses
(friends). Friends Only mode is controlled by S-Register 82, that enables
and disables the comparison of packet source addresses against a list
stored in the DART 200’s destination dial directory. Refer to the Modem
dial directory, p. 8-24 AT&Z command in Appendix F, DART AT
Command Set, for details. Only the IP Address portion of the addresses
in the dial directory is used with this feature. Bit 0 of S-Register 82
controls this mode. The default is to accept all incoming datagrams (bit 0
= 0).
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This bit is significant only when the TCP connection is established
passively (server mode). When the connection is established actively (by
an ATDT command), incoming packets are accepted from the
destination address specified in the dial command regardless of whether
or not it is contained in the friends list.
In both modes of operations, the source address (IP Address and port
number) of the last accepted packet is saved in a temporary variable for
use as the current destination address for all packets being sent by the
MAS during the current session. This source address information is also
saved in S-Register 53 where it can be obtained with an ATS53?
command.
TCP communication
To participate in a TCP session the DART 200 must be registered on the
CDPD system. Refer to Channel acquisition, p. 2-10, and Registration,
p. 2-15 for details on registering the DART 200 on the CDPD network.
A TCP session can be started by the central site system (host or F-ES) or
remote system (MAS); it is application dependent. If the MAS is the
client it starts a session with the ATD command and the T (for TCP)
modifier followed by the host IP Address and port number (Ex.
ATDT198.225.176.43/2100). If no port is specified the port number
defaults to the standard telnet port (23); this should be avoided.
Unless the application is being run on a closed system, use port numbers
between 1025 and 4999 for compliance with industry standards.
Alternatively, the dial could reference an IP Address/port stored in the
DART 200 dial list by the ATDTSn command where n is the position
number of the desired IP Address in the dial list. Refer to the &Z
command in Modem dial directory, p. 8-24, Appendix F, DART AT
Command Set, for more details.
When a connection with the server is established:
1. The modem enters online mode and presents a CONNECT response
to the MAS. It is customary (but not required) for the client to do the
first data transmission.
2. The MAS begins data transfer by writing application data to the
DART 200 through the RS-232 port using device specific
commands.
3. This data is assembled until a data forwarding condition occurs, as
described in Data forwarding, p. 8-8.
4. The DART 200 attaches the TCP header and sends the packet onto
the network.
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5. The data packet is directed by the network routers to the appropriate
port on the designated server. If the server or the data path becomes
inactive between the time the connection is established and the time
data transmission starts, the MAS is informed by an error message
being returned.
If the central site is the client establishing the TCP session, the modem at
the remote site must be set up in TCP sever mode. The MAS can wait for
a RING message and respond with an ATA command, or its modem can
have auto answer active. Refer to Auto Answer setup, p. 8-11, for details
on activating this option.
?
Time-outs are not a
consideration if auto
answer is enabled.
NOTE:
Unlike UDP, with TCP a session is established by a three-way handshake
between the client and the server, not by the initial datagram. The client
IP Address is part of the incoming session establishment packet. When
the TCP handshake is received by the TCP server, the modem first
validates the source address (if the Friends Only option was specified).
If the source address is acceptable or if Friends Only is not active then a
RING result code is issued.
·
If auto answer is active the CONNECT message is issued. If not,
then an ATA must be issued by the MAS within 60 seconds or the
tentative connection will be dropped.
·
The modem extracts the source address (IP Address and port
number) from the handshake packet for use in constructing the
response data packets and also stores it in S-Register 53. This data
can be retrieved by the end-user application, if needed, with an
ATS53? The address data cannot be viewed with the AT&V
command:
?
NOTE:
The address remains in
S-Register 53 until the
session is ended by an
ATHn command.
ats53?
198.225.189.21.4000
·
The modem enters online mode.
If the source address is not acceptable, the connection is refused.
In either client or server mode:
1. When the connection is established a CONNECT message is
received.
2. The MAS continues to read from (server) or write to (client) the
serial port to exchanges data packets with its session partner.
3. If data is being sent, it accumulates until a data forwarding condition,
as described in Data forwarding, p. 8-8 occurs:
·
·
The DART 200 then attaches the TCP header and sends the
packet onto the network
The packet is directed by the network routers to the appropriate
port on the designated server
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4. Once the data block is received it is ready for processing. Any
necessary error-checking, resequencing, and so on, is handled by the
TCP software and is not the responsibility of the MAS. The handling
of network connectivity issues (such as loss of carrier), as opposed to
data delivery and sequencing (provided by TCP), is the responsibility
of the MAS. Refer to Error recovery, p. 8-4, for guidelines on error
handling.
5. Once the first data block has been received, the server system (MAS
or central site depending on application design) could reply to the
client system with data of its own, or it could wait for additional data
from the client. The variations at this point are numerous and entirely
dependent on application design.
6. When data transfer is complete the session terminates. As with the
initial communication step, either end could terminate; it is another
application design decision, but usually, the client terminates.
7. If the MAS is the server, it receives a NO CARRIER message and
returns to command mode when the client terminates the session. If
the MAS is the client, it performs an escape function to return to
command mode followed by a hang-up command (H). Refer to
Appendix F, DART AT Command Set, for a description of H.
Setup options
The following items must be set to enable the DART 200 to operate on
the CDPD network:
·
IP Address (^A)
·
·
Side Preference - \N in the modem profile
Channel restrictions - \J in the modem profile
Refer to Basic modem personalization, p. 2-6, for a review of the details
on the AT commands ^A, \N, and \J.
In addition the following items are required for basic TCP operation:
·
·
Automatic registration. Refer to p. 8-6 for details
PAD mode - \O0 in the profile. Refer to \O command in Appendix F,
DART AT Command Set
If application design dictates that the MAS accepts connection requests,
activate the TCP server by setting the *A (select server type) AT
command to 1 with an AT*A1. Selecting this option enables the TCP
server function. The default value for this parameter is *A0 (no server
active). The default option is appropriate if the MAS application always
operates in client mode; always originates the connection request with an
ATDT command.
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Many of the following profile parameters apply and need to be evaluated
before proceeding to step 1. Some need to be set to provide the proper
application operating environment, and others can be allowed to default.
Review application programming in Chapter 8, Application
Programming, and the command descriptions in Appendix F, DART AT
Command Set.
·
Command mode echo (En)
Data set ready (DSR) operation (&Sn)
Verbose mode (Vn)
Data forwarding operation (\Fn)
Quiet mode (Qn)
Manual transmit control (\Mn)
Online mode echo (Fn)
Flow control (\Qn)
Extended result codes (Xn)
Automatic transmit control (\Tn)
Data carrier detect (DCD) operation (&Cn)
TCP PAD Keep-alives (*Kn)
Data terminal ready (DTR) operation (&Dn)
Set Listen Port (*Ln)
·
·
·
·
·
·
·
·
·
·
·
·
·
·
Escape code recognition (&En)
1. Set the key parameter, PAD Operating mode (\On), to \O0 for TCP
operation.
2. If the modem is to be set up as a server to answer incoming calls
(connection requests), select the method to be used. There are two
options available: setting S-Register 0 = 1 with an ATS0=1
command is the preferred method. This option puts the modem into
permanent auto answer mode. The alternative is for the MAS to wait
for the RING message, indicating an incoming connection request,
and then use the answer command, ATA, to establish the connection.
3. Select the port for the DART 200 to listen on for incoming messages
with *L command by using an AT*Ln, where n is the desired
listening port. Unless you are operating on a closed network, use a
decimal number in the range of 1025 to 4999 for compliance with
industry standards. The default value for the listening port is 2100
for backward compatibility with earlier versions of the modem.
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4. In any TCP application where the remote system only operates in
server mode, consider the use of the TCP keep-alive option (*K). It
is possible for the central client system to fail after establishing a
session with a remote server. If the client fails its end of the TCP
session closes, but the server end remains open.
Attempts to re-establish the connection with the server after the
client recovers get a BUSY response because the prior session was
not properly closed. The receive keep-alive option (*K2) enables a
remote server to close its side of a session if data or a keep-alive
character is not received within an end-user specified timeout period.
The time out period is contained in S-Register 86 (default 120
minutes). A reasonable timeout value is on the order of 3 to 5
minutes.
The remaining parameters are application dependent and are covered in
detail in Chapter 8, Application Programming.
Sample TCP setups
These settings give a general sense of the AT commands required to set
up a DART 200 for a TCP application. All relevant AT commands are
listed, even the defaults. All devices function differently, therefore, the
setups listed in this section of the manual are general. These setups show
specific items to examine, but it is a good idea to examine all of the setup
values.
Two TCP setup examples are shown below: a remote telemetry
application and a central client application. Remote TCP setup, p. 5-19
shows the setup for a server modem at a remote telemetry unit (an RTU)
being polled by a host computer.
Host TCP setup, p. 5-21, shows the setup for a client modem at the host
computer that does the polling. This modem at the host arrangement is
suitable for bench testing and limited use pilot implementations.
Production systems normally are direct connected through a leased line
or frame relay to a router at the customer’s host system (F-ES).
Remote TCP setup
The remote modem is set up as a server at the remote telemetry unit
where it responds to polls from a host computer. The specific RTU does
not use flow control and the data being sent is binary, not character, data.
This requires the TCP server with auto answer to respond to polling, no
flow control, and timed data forwarding because of the binary data.
In Table 5-3, the line items marked with an R (required) or an O
(optional) are changed from the default (D).
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Table 5-3. Remote TCP setup
AT Command
Req Opt Def Description
AT^Annn.nnn.nnn.nn
n
Input IP Address (if not already
done)
R
AT\N[1,2]
AT\J0
Side Preference (get from carrier)
Use default - No channel access
restrictions
Auto Registration at Power On
With AT\R4 sets Continuous
Automatic Registration
R
D
AT\R4
ATS13=0
R
R
AT\O0
AT*A1
ATS0 =1
AT*L2100
ATE0
PAD mode is required for TCP
Sets TCP Server mode
Set modem to Auto Answer
Use default - Listen on port 2100
No command mode character echo
Use terse result codes
R
R
O
D
O
O
D
ATV0
ATQ0
Use default - Result codes are sent to
the RTU
ATF1
D
Use default - Do not echo
transmitted data to the RTU
Use default - Extended result codes
Use default - DCD follows state of
the connection
Use default - You may want to
consider using DTR to escape if
RTU supports it
ATX1
AT&C1
D
D
AT&D0
D
AT&E2
AT&S0
AT\F3
Filter escape sequence from output
Use default - DSR is always active
Use default - Applies only if \M1
specified
Use default - Do not recognize data
forwarding characters
O
D
D
AT\M0
D
AT\Q0
AT\T1
Most RTUs do not use flow control
Use default - Timed data forwarding
should always be used with binary
data
O
D
AT*B0
AT*C1
AT*G1
AT*K2
ATS86 = 3
AT*R0
AT*T0
D
D
D
O
O
D
D
Use default - Does not apply to TCP
Use default - Does not apply to TCP
Use default - Does not apply to TCP
Set TCP receive keep-alives
Use 3 minute keep-alive timeout
Use default - Does not apply to TCP
Use default - Does not apply to TCP
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Host TCP setup
The host (client) modem is set up to support polling of remote devices by
the host computer. The host uses flow control and the data being sent is
binary, not character data. The polling function does not require the TCP
server, but requires flow control, and timed data forwarding because of
the binary data.
Use this setup only for bench testing or a limited use trial. A production
application uses a leased line, frame relay, or Internet connection
between the host and the MDIS instead of a modem. In the latter
scenario, the production host application needs to include a software
stack (replacing the modem stack) to operate with the CDPD network.
In Table 5-4, only the line items marked with an R (required) or an O
(optional) are changed from the default (D).
Table 5-4. Host TCP setup
AT Command
AT^Annn.nnn.nnn.
nnn
Req Opt Def Description
Input IP Address (if not already done)
R
AT\N[1,2]
AT\J0
Side Preference (get from carrier)
Use default - No channel access
restrictions
Auto Registration at Power On
With AT\R4 sets Continuous Automatic
Registration
R
D
AT\R4
ATS13=0
R
R
AT\O0
AT*A0
AT*L2100
ATE0
ATV0
ATQ0
PAD mode is required for TCP.
Use default - No server required
Use default - Listen on port 2100
No command mode character echo
Use terse result codes
Use default - Result codes are sent to the
host
Use default - Do not echo transmitted
data to the host
R
D
D
O
O
D
ATF1
D
ATX1
AT&C1
D
D
Use default - Extended result codes
Use default - DCD follows state of the
connection
AT&D0
D
Use default - You may want to consider
using DTR to escape
AT&E2
AT&S0
AT\F3
Filter escape sequence from output
Use default - DSR is always active
Use default - Applies only if \M1
specified
O
D
D
AT\M0
AT\Q2
AT\T1
D
D
D
Use default - Do not recognize data
forwarding characters
Use default - Most PC’s use flow
control
Timed data forwarding - Always use
with binary data
AT*B0
AT*C1
AT*G1
D
D
D
Use default - Does not apply to TCP
Use default - Does not apply to TCP
Use default - Does not apply to TCP
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Table 5-4. Host TCP setup (cont.)
AT Command
AT*K0
Req Opt Def Description
D
Use default - Keep-alives not needed at
central site
AT*R0
AT*T0
D
D
Use default - Does not apply to TCP
Use default - Does not apply to TCP
SLIP
Serial Line Interface Protocol (SLIP) is the defacto standard for
encapsulating TCP/IP protocol over dedicated and/or switched serial
lines. It is a useful and reliable way to allow mixes of hosts and routers to
communicate with one another in various combinations.
Most casual end-users do not encounter SLIP in the above form. Instead,
they find SLIP being used with TCP/IP stacks (usually referred to simply
as stacks) in a variety of PC programs designed to provide support for
multiple TCP or UDP applications over networks of various types (X.25,
LANs, satellite, and so on) including the Internet. CDPD is another such
network.
These stacks frequently include additional functions such as electronic
mail, various forms of telnet, ping, Internet browsers, and file
downloading using File Transfer Protocol (FTP). In addition, most of
these programs provide a multitasking end-user application programming
interface (API) to the stack (usually, Winsock), for developing custom
communications applications. These programs are also used with PCs
attached to the CDPD network.
The DART 200 provides SLIP capability. When operating in SLIP mode,
the modem’s internal TCP/IP stack is bypassed (but not its CDPD stack)
and, the modem acts as a router passing data between the software
package’s stack, and the network, such as the Internet or a private
network using Internet Protocol, attached server applications.
Using such a package allows the design of applications that need
multiple communications sessions active concurrently. For example, a
public safety application where a police car has active sessions
simultaneously with the NCIC in Washington, the State Bureau of Motor
Vehicles, and the local police system.
Modem setup for SLIP
In SLIP mode, the following profile parameters are not operational and
can be ignored. Their function is provided by the PC-based software
package.
·
·
·
Data forwarding operation (\Fn)
Select Server Mode (*An)
Manual Transmit Control (\Mn)
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·
TCP/IP keep-alives (*Kn)
·
·
·
TCP PAD operating mode (\On)
Telnet keep-alives (*Tn)
Automatic transmit control (\Tn)
The following profile parameters are operational in command or SLIP
modes and need to be evaluated to determine their proper settings:
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
Command mode echo (En)
Data set ready (DSR) operation (&Sn)
Online mode echo (Fn)
Restrict Channel Selection (\Jn)
Quiet mode (Qn)
Side preference (\Nn)
Verbose mode (Vn)
Flow control (\Qn)
Extended result codes (Xn)
Reception of IP broadcasts (*Bn)
Data carrier detect (DCD) operation (&Cn)
SLIP TCP header compression (*Cn)
Data terminal ready (DTR) operation (&Dn)
SLIP Multicast address selection (*Gn)
Escape code recognition (&En)
Automatic SLIP Restart (*Rn)
SLIP Header Compression (*C) and Flow Control (\Q) are the key
parameters. They must match the stack settings for SLIP to operate.
1. Setting SLIP header compression on saves a small amount of time
(recommended) in data transfer. In most commercial software stacks
this feature, if offered, is identified as CSLIP. The default setting for
this parameter is *C1 (enabled). If this setting and that of the stack
do not match SLIP cannot operate successfully. If your stack does
not support compression, you must deactivate it on the DART. To do
this execute an AT&C0, and save it with an AT&W.
2. Use hardware flow control (\Q2 - default). If this setting and that on
the stack do not match SLIP cannot operate successfully. Software
flow control or no flow control are inappropriate.
3. Set Channel Restrictions (\J), and Side Preference (\N)
appropriately, as described in Basic modem personalization, p. 2-6,
but these settings are CDPD, not SLIP related.
4. Set the COM port for 8 data bits and NO parity (8N1). Since SLIP
operates in binary mode, a data byte could be any 8-bit
configuration, so parity must be disabled to permit proper operation.
5. Set the DART 200 COM port speed to match that of the stack: 19.2
Kbps is recommended. This can be accomplished by an AT&L &W
command.
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Automatic SLIP restart specifies that the DART 200 always enters SLIP
mode following power on or modem reset. It lets Winsock applications
rely on the modem always being in SLIP mode, particularly following a
power off/on cycle.
When this feature is active the modem is not in command mode
following power on. This can sometimes be inconvenient. Any time that
it is necessary to send AT commands to the modem, at initial application
startup or when querying modem status an escape function must be
performed (refer to &E or &D commands) before the modem responds
to AT commands. If using the manual escape function, check that both
the terminal emulation program and the modem are set to the same baud
or the escape will not work.
1. This capability is activated with an AT*R1 command (deactivate it
with an AT*R0). Bit 6 of S-Register 57 (value of 64) indicates that
auto slip mode is active. A modem that acquired a CDPD channel
(128), and used the auto registration feature (32) to get registered (1)
shows a value of 225 in S-Register 57 with Auto SLIP Mode Startup
(64) active.
2. Save the setting with the &W command to become a permanent
setting.
3. To make the command active, power cycle or reset the modem with
the AT-R command.
SLIP IP Address overview
·
Internet Address Classes
CDPD Internet addresses are 32-bit fields consisting of a network ID
followed by a device ID (netid, devid). For readability, these 32-bit
addresses are broken down into four 8-bit fields (called octets or
bytes) that are then converted to their decimal equivalents and
separated by a period. For example, the address 11000000 00001110
10100111 00010101 (hardly readable) is represented as
192.14.167.21
Internet standards further define five classes of addresses, the first
three (A,B, and C) of which are used for network addresses.
·
·
·
Class A addresses have a first octet between 1 and 127, and
consist of a one octet network address followed by a three octet
device address
Class B addresses have a first octet between 128 and 191, and
consist of a two octet network address followed by a two octet
device address
Class C addresses have a first octet between 192 and 255, and
consist of a three octet network address followed by a one octet
device address. Most CDPD addresses are class B or class C
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A simplified block diagram of a terminal connection to a CDPD
network using the SLIP interface is shown in Figure 5-1.
Figure 5-1 Terminal connection to a CDPD network using SLIP
RS-232
Link
AirLink
#1
#2
#3
CDPD
Network
MAS
(Terminal)
M-ES
MC-DART
#1 - Local Terminal (MAS) IP Address
#2 - DART SLIP Interface IP Address
#3 - DART (registered NEI) IP Address
The three IP Addresses are:
1. Local Terminal (MAS) IP Address is set using by AT*Mn.n.n.n
This MAS address is not known to the CDPD network, so it is set by
convention to the same value as the one used for #3, as described in
item 3 on p. 5-25, to improve performance of the DART 200’s
routing mechanism and to ensure that FTP protocol works properly.
2. The DART SLIP Interface IP Address is set using the service
provider command AT^Sm.m.m.m
The SLIP IP Address is an arbitrary value, usually 1.1.1.2, because it
is only used by the MAS and DART 200 and is not known to the
network. In the definitions for commercially available stacks used
with SLIP this IP Address is referred to as the router, gateway, or
server address. This address must be present in SLIP definitions for
your stack or you cannot run SLIP with the DART 200.
There are two issues involving this address to consider:
·
Some TCP/IP software stacks do a validity check on all of these
addresses and require them to be of the same class as the NEI
·
The SLIP IP Address must be on a different subnetwork than the
NEI. If it is not, the DART cannot route packets (pings included)
to the CDPD network
The suggested resolution to these constraints (if 1.1.1.2 does not
work) is to set the network (class) portion of the DART SLIP address
to be off by one from the NEI’s network address, and to set the
device address to all ones, for example:
Class
NEI
SLIP Address
Class A 111.155.189.21
Class B 155.160.147.17
110.1.1.1
155.161.1.1
Class C 196.37.111.165
196.37.110.1
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3. The DART (registered NEI) IP Address is known to the network and
is obtained from your service provider. This IP Address is set using
the following service provider command: AT^An.n.n.n/x, where: x
defines which slot (0-9) in the address table to use. If not entered, x
defaults to 0.
If there is more than one NEI stored in the modem’s NEI list the
desired one is selected by using the following command: AT\Sn,
where: n = 0 to 9
The IP Address selected for use as the NEI remains fixed until
specifically changed by using the AT\S command.
?
NOTE:
To view the list of IP Addresses as well as the MAS and SLIP IP
Addresses use the AT\S? command: the active NEI has an * to its
left, for example:
·
·
·
All three IP
Addresses cannot
be the same
at\s?
For FTP, #1 and
#3 (in Figure 5-1)
must be the same
All three can be
different for
SLIP = IP ADDRESS 001.001.001.002
MAS = IP ADDRESS 155.174.048.173
NEI 0 = IP ADDRESS 155.174.036.087
*NEI 1 = IP ADDRESS 155.174.048.173 SPNI 00000 LSA
00000
non-FTP
communications,
but performance is
somewhat better if
#1 and #3 are the
same
OK
SLIP operation
The SLIP operation process is as follows:
1. SLIP starts with the AT*S command.
2. This command puts the modem into SLIP mode and gives an OK
response.
3. When in SLIP mode the DART 200 passes all IP and higher layer
protocols (TCP, UDP, telnet) to the TCP/IP stack in the MAS for
processing, but continues to handle the lower CDPD protocol layers
including the data encryption function. Data forwarding defaults to a
transparent, symbol-based method where the symbol is the SLIP
end-of-packet character.
4. The modem stays in SLIP mode until an escape function is
performed by the end-user application; by either sending the escape
sequence, or by dropping DTR.
5. To return to SLIP mode another AT*S must be issued.
An example of SLIP setup for Trumpet, a commonly available shareware
Winsock, is shown in Appendix D, SLIP Setup Examples.
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SLIP initial testing
After the IP Addresses are set, the SLIP setup is completed, and the
modem has been put into SLIP mode, determine if your setup is correct
and that you have network connectivity by pinging the network.
The ping command format can vary slightly depending on the program
you are using. However, the following discussion provides basic
guidance regardless of the TCP/IP stack used. The general format of the
ping command is: PING nnn.nnn.nnn.nnn
The ping sends a fixed length of data (L) with an echo request to IP
Address nnn.nnn.nnn.nnn and waits for a time out period (T) for a
response. L and T can be quite different from one program to another, as
well as from the DART 200 ping values used with the AT*P command.
Consider the differences in these values between your program and the
DART 200’s AT*P when comparing results.
The DART 200 default ping values are L= 68 bytes, and T=10 seconds,
that result in ping times in the range of 600 to 1600 ms. Most SLIP
packages use a larger L and a smaller T than the DART 200, because
they were originally designed for land lines or Local Area Networks
(LANs) where ping times are much faster than with CDPD. Executing a
SLIP ping with its own default parameters over CDPD frequently causes
time-outs. If this occurs shorten the SLIP ping data length or increase the
timeout period to get successful pings.
To validate that you have set up the SLIP session between the DART
200 and the stack correctly:
1. Ping the modem. Make the modem’s SLIP address (1.1.1.2) the
target. If this ping operation is successful it demonstrates that your
setup is correct. This test can be done without being registered or
without CDPD being active.
P
TIP:
It's helpful when testing
to have two DARTs to
ping between. This
gives you control over
both ends of the link,
and can be done using
a single PC. Register
the first DART using
your PC, then switch
the PC to the second
DART, bring up SLIP,
and ping back to the
first modem. A
2. Ping the DNS or a server at the local carrier. This Server IP Address,
like the DNS, is available from the carrier. If this ping operation is
successful, the SLIP system can communicate with the carrier.
If the ping fails and you are using a modem SLIP address other than
1.1.1.2 , you may have a routing problem. Refer to item 2 on p.5-25,
for guidance.
3. Ping an IP Address on the other side of the MDIS; usually, this is a
server, or a test terminal near you.
If this is successful, your SLIP system has network connectivity and
is now fully operational. If this ping attempt fails for reasons other
than time-out, suspect a bad IP Address, an unregistered IP Address,
or a router failure at the MDIS.
registered modem does
not need an attached
PC to respond to a
ping provided it is not
in SLIP mode.
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Telnet
The telnet capability within TCP/IP is designed to provide support for
ASCII terminals to communicate with text-oriented server applications
on host systems. As implemented in the DART 200, the telnet support
mode provides the capability for the modem to emulate such a terminal;
the default is the DEC VT100 but the actual type is negotiated with
(dictated by) the server.
A device (usually a PC, but potentially an ASCII terminal) attached to
the DART 200 and using telnet mode has its data stream translated to
that of the VT100 or whatever other terminal type was negotiated. This
usually involves not only translating a few control characters, but also
turning off the high order bit of each data character. This translation can
make it very awkward to use telnet mode for a typical telemetry
application. It is strongly recommended that telnet not be used for other
than the intended use; providing access to ASCII terminal application
servers.
Setup options
With the exception of the side preference, the DART 200 factory defaults
permit a telnet session to be established. However, certain profile
parameters need to be checked to ensure they work appropriately with
the remote host at minimum cost, as follows:
·
Online Mode Echo (ATFn) - Controls the echoing of characters
when in online mode. The default for telnet mode is F1 (host echo)
When a telnet session starts, one of the items that the DART 200
negotiates with the host is whether the host or modem provides the
echo for characters entered at the modem end of the connection.
Most processes connected on the well-known telnet port (23) provide
the echo. However, in a CDPD telnet session where charges are
based on packet and data flow rather than on connect time, there is a
big incentive to minimize the flow of extraneous information; use the
F0 option (modem echo) to do this.
The tradeoff is one of cost versus the confirmation that the characters
arrived correctly, which is presumed if they echo back correctly from
the host. Also, the client has no knowledge of how certain characters,
such as a backspace (BS), should be handled locally since the remote
process is what determines if a BS is destructive or harmless.
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·
Data Forwarding Operation
·
Manual Transmit Control (AT\Mn) - Controls the use of the
characters (specified in S-Registers 51 and 52) for data
forwarding while in online mode. The default for this parameter
is \M0 (disabled). The default for S-Register 51 is <CR>, that
takes effect only if manual transmit control is enabled.
·
Automatic Transmit Control (AT\Tn) - Controls the use of the
inter-character time-out period (specified in S-Register 50) for
data forwarding when in online mode. The default for this
parameter is \T1 (enabled)
With the defaults listed above in effect, characters are
transmitted to the telnet host process (remote login or gopher)
and echoed back from the remote system for display as they are
entered. This generates a lot more packets, but ensures an
accurate display of the data as seen by the host application.
If your telnet host process operates correctly with, or requires
block mode data transfers (a string of characters followed by a
<CR>), then set local echo (F0), manual transmit mode enabled
(\M1, and disable inter character data forwarding (\T0). A local
echo is recommended, in this case, so you can view keys as you
enter them without pressing the <CR> key.
·
Telnet Keep-Alive - Allows the DART 200 to keep a telnet
session alive (not time out) if the terminal user has excessive
think time between entries. Without this capability the telnet
session could be terminated prematurely by the server
This facility can work in transmit mode, receive mode, or both. It
uses a non-intrusive telnet NOP command packet and a
keep-alive time-out value (S-Register 86) to implement the
function. The keep-alive timer restarts when data is sent or
received regardless of the mode selected (transmit, receive, or
both).
If the timer expires with the transmit option specified, pending
data or the telnet NOP command is forwarded. If the NOP
(keep-alive) is sent the telnet server protocol ignores it, but the
session is not allowed to time out. This is the normal use of the
function.
If the timer expires with the receive option specified, an ATH
command is issued to close the connection.
The default for this function is *T0 (not enabled). Refer to the
*T command in Appendix F, DART AT Command Set, for details
on how to use this command.
·
Linefeed after <CR> - S-Register 1 controls whether or not a linefeed
(<LF>) is sent with a carriage return (<CR>), for telnet mode only.
The default is 1 (send <LF> with <CR>). When not enabled, a NULL
character follows the <CR> as specified by telnet protocol
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·
Terminal Emulation Negotiation - S-Register 78 determines the
terminal emulation type to offer first when negotiating with the telnet
host system. The current list is:
·
·
·
0 = DEC-VT100 (default)
1 = DEC-VT52
2 = UNKNOWN
Default is for most specific first, such as 0. When the telnet session is
established and negotiation is complete, the actual terminal type chosen
is determined by using the telnet escape mode status command, or by an
appropriate command for the remote server. If UNKNOWN was
selected, the backspace and delete keys may not work correctly. If this is
the case you have two options:
1. Use the erase character definition on the remote server. UNIX
usually uses the tset, stty, or printen commands to access terminal
parameters. Refer to a UNIX manual or ask the serving system
administrator.
OR
2. Use the telnet virtual terminal erase character command to send the
erase character.
Telnet escape commands
When in a telnet session, entering a Ctrl ^ means that telnet interprets the
next keystroke as a command. The commands include:
e
i
l
r
Send Telnet Virtual Terminal erase character command.
Send Telnet IP command (Interrupt Process).
Tell server you are going to local echo mode
Request server to perform remote echo usually responds [YES] if
there
a
Send a telnet AYT Are You There (AYT) command; Server
usually responds YES if there
b
o
s
Request Binary Mode. This is not normal, use with caution
Request to turn Binary Mode off
Print current status of telnet session. (Local parameters)
Send the local telnet escape character.
^
Any other key that follows the ^^ sequence displays a list of allowed
commands. S-Register 77 contains the telnet escape character (default is
^^ or decimal 30.
Some of the DART 200 profile parameters (\Mn,\Tn, and so on) can be
changed after logging in to the telnet host by using the DART 200’s
escape to command mode sequence (+++). However, do not change
S-Register values and modem profile parameters that were negotiated
with the remote host when in the connected state, since changing their
values at this point could impact client/remote host communication.
After completing your changes, return to the telnet session with the ATO
command.
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New for this version
The telnet binary mode (\Bn) was removed from the AT command set,
because a telnet remote login session should not be started with this
function enabled.
Binary mode considerations
Binary operation is available for telnet but only as a telnet escape
command. Requesting binary mode does not guarantee that it can be
established because the option is negotiated with the remote host. Query
telnet status after requesting binary mode to determine this, but do so
with caution.
Software flow control cannot be used since XON/OFF characters in the
data stream can not be distinguished from data with the same bit format.
Also, escape data streams containing the telnet escape command
character should be escaped by doubling the character. For example, if
the escape character is ^^ (decimal 30) and it appears in the binary data
stream, then modify the data by inserting a second escape character
adjacent to the first, for example:
1. Original data stream
·
·
Data to modem [...69,123,24,30,49,....]
Data from modem [...69,123,24,49,....]
?
2. Modified data
NOTE:
Telnet servers are usually
quite slow, so be patient
when waiting for the
CONNECT message, and
again for the login
screen. Usually, after the
LOGIN session
·
·
Data to modem [...69,123,24,30,30,49,....]
Data from modem [...69,123,24,30,49,....]
If binary data transfer is needed, the telnet mode of operation is probably
not the appropriate mechanism to use. The need to negotiate the option,
and the need for doubling the telnet escape character tend to make the
function awkward. Non-telnet modes such as UDP or TCP are much
better suited to binary data transfer.
operations speed up.
Follow the instructions
from the server to run
and terminate your
Telnet operation
session. Usually, when
you quit the telnet session
the server breaks the
connection and a NO
CARRIER message
appears. If this does not
happen, escape from
online mode with the +++
escape sequence and
hang up with an ATH0.
When the setup options are complete (\O1, \F0, \M1, \T0 are
recommended) establish a telnet session by dialing a telnet server, for
example, a bulletin board with an ATDTn.n.n.n/p command; where
n.n.n.n is the IP Address of the telnet server. The port number (p) is not
required because it defaults to the standard telnet port number (23).
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6
Device Attachment
RS-232 connection
The DART 200 has an RS-232 DB9 interface. If the remote device has a
similar interface, then any standard PC communications cable functions
as a connector between the two. Otherwise, refer to Data and control
interface, p. 8-14, for a discussion of the RS-232 leads and the minimum
number required for operation.
Standard RS-232 communications cables function properly for distances
up to 50 feet. If longer lengths are required, low loss RS-232 cable or
electronic cable extenders can be used; both are available from local
cable distributors or electronic catalogs.
Null modem function
The RS-232 interface specification was defined before the invention of
microcomputers. The original intent was to standardize the method that
computers and terminals used to communicate remotely over telephone
lines. The standard specification is generalized in Figure 6-1.
Figure 6-1. Standard RS-232 connection
DTE
DCE
DCE
DTE
RS-232
Phone
Line
RS-232
Computer
Terminal
Modem
Modem
The RS-232 standard specified the label Data Terminal Equipment or
Data Terminating Equipment (DTE) for terminals and computers, and
the label Data Communications Equipment (DCE) for modems. The
popularization of RS-232 serial communications resulted in many
different types of equipment, besides modems, that employ the standard.
Many manufacturers expect devices to connect directly to DTE
equipment (usually, PCs). Consequently, devices are designed with a
DCE interface, so a standard RS-232 cable meets the cabling
requirements. Common usage of RS-232 is shown in Figure 6-2.
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Figure 6-2. Stand-alone RS-232
DTE
DCE
RS-232
Computer
Terminal
The problem with this occurs when modems are inserted between the
DTE and a remote device with a DCE interface. The modem expects to
communicate with a DTE interface. Since this is not the case at the
remote end, where the DCE modem is trying to talk to a DCE device, a
communications failure results. The solution for this situation is a null
modem connector. A typical null modem pin out is shown in Table 6-1.
Table 6-1. Typical null modem pinout
Female
DB9
Male
DB9
1 DCD
2 RXD
3 TXD
4 DTR
5 SGD
6 DSR
7 RTS
8 CTS
9 ---
4
3
2
6 and 1
5
4
8
7
Open
The null modem adapter corrects the mismatch between the modem and
a terminating device having a DCE interface. The proper location for the
null modem is shown in Figure 6-3.
Figure 6-3. Null modem location
DTE
DCE
DCE
DCE
RS-232
Phone
Line
RS-232
Computer
Terminal
Modem
Modem
Null modem
needed here
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To identify this problem connect a PC directly to the device and establish
communication. If communication is established, the device uses a DCE
interface and requires a null modem to communicate with the DART
200.
Null modem adapters are available as stand-alones; that look like an
RS-232 gender-changer, or as null modem cables. Null modem adapters
are available from electronics stores and are well suited for application
development. Null modem cables can be ordered from cable suppliers,
and are better suited for field deployment, because the cables eliminate
the extra part and failure prone connections required for a stand-alone
null modem.
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7
Vehicle Installation
Considerations
Electrical transients
When a Data Access Radio Transceiver (DART) 200 is installed in a
vehicle it is usually powered from the vehicle’s electrical system.
Transients or temporary outages that can occur during starts or other
vehicle operations, can cause the DART 200 to reset the power. These
transients can also impact the attached Mobile Application Subsystem
(MAS).
There are several options available to minimize or eliminate vehicle
power disturbances, including filters, cut off switches, and universal
power supplies. The best solution; however, is to compare the needs of
the application and equipment to the cost of the proposed solution. Try
alternatives during testing to avoid problems during application roll out.
The simplest power backup system is a 12-volt battery; large enough to
supply the modem’s maximum transmit current, with a blocking diode to
prevent discharging the battery into the vehicle’s electrical system. The
battery floats on the vehicle’s 12 volt DC power system, constantly being
recharged, and used only during periods of transient voltage drop. The
diode prevents the vehicle’s electrical system from drawing power from
the backup battery during these voltage drops.
The diode needs to allow at least 2.5 amps of current in the forward
direction, and withstand a reverse voltage of at least 20 volts. Higher
rated diodes, available at a nominal cost from electronic stores, dealers,
and catalogs, provide a better safety factor.
Application considerations
Resets can occur during or between communications with the remote
system. The most serious situation occurs if the reset happens during
communications, because the modem switches from online to command
mode. If the reset occurs between communications, the impact can be
less critical because many applications take the modem out of online
mode during this time period anyway.
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The application program in the MAS has no way of knowing before
attempting a send or receive operation if the modem is still in online
mode. The application can be designed to assume that the modem is
always online, or to always check that it is online before performing the
send or receive operation. In the former case, a send operation failure is
indicated by an error return code (in command mode the modem expects
to see all messages start with an AT), while a receive failure is indicated
by a timeout.
If the MAS can sense the RS-232 interface, as described in CDPD status
sensing, p. 8-15, perform this operation to verify that the modem is still
connected before attempting a send/receive operation. For Transmission
Control Protocol (TCP) or User Datagram Protocol (UDP) the connected
state implies that the modem is online. If the MAS cannot sense the
interface leads, it tries the send/receive operation first, and only proceeds
to error-checking if an error or timeout occurs.
For applications using Serial Line Internet Protocol (SLIP), use the
Automatic SLIP restart feature on the modem, to automatically put the
modem back into SLIP mode following a power reset.
If the modem is not online, the next step is to check registration state
through the RS-232 leads or with ATS57? If it is not registered, the
program waits and periodically checks registration status, eventually
proceeding when the modem reregisters. It is assumed that the modem is
set up to register automatically, as described in Auto-Registration when
not registered, p. 8-7.
When the modem becomes registered, the next step depends on whether
or not the MAS is a server or a client. If it is a client, the recovery
procedure for both TCP and UDP is to issue the appropriate dial
command. If it is a server, the recovery procedure for both TCP and UDP
is to wait for a call from a client.
Proximity to other antennas
In general, do not locate the DART 200 antenna closer than 5 feet to
other antennas (specifically, two-way radio antennas) and in certain cases
more separation is required. In many vehicular applications, there are
two-way radio transmitters in use and usually the antenna mountings are
not 5 feet apart. Interference from the radio transmitter can slow down
response times or block modem transmission.
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In this situation, separate the antennas as far as possible and then run a
field test when the two-way radio is also being used. If the DART 200
works satisfactorily you do not have a problem, but if it does not filtering
is required. A bandpass filter on the two-way radio’s transmitter output
eliminates harmonics that can interfere with the cellular frequencies. A
band reject filter on the DART 200’s input, centered on the two-way
radio’s base frequency, provides signal attenuation at that frequency to
help prevent de-sensing the DART 200’s Radio Frequency (RF)
circuitry: either, or both can be required. The calculation to determine the
filtering usually requires an RF engineer.
If you do not have the option to field test, then the theoretical calculation
approach is your only option.
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Chapter
8
Application Programming
The Data Access Radio Transceiver (DART) 200 offers built-in
Transmission Control Protocol (TCP), User Datagram Protocol (UDP),
Serial Line Internet Protocol (SLIP), and telnet support, but most
end-user application programming that interacts with the modem uses
TCP, UDP, or SLIP.
Telnet is used primarily as a path to applications on remote hosts with
the local device being an ASCII terminal or, more likely, a PC emulating
an ASCII terminal. Outside of setting up the modem initially to meet
telnet’s needs, there is no programming to do. Error handling is provided
by the ASCII terminal emulator and is usually minimal.
This chapter is directed at TCP and UDP applications, and DART 200
solutions, particularly for DART 200 error handling. SLIP mode
applications function similarly, but the specifics are a function of the
capabilities of the software stack being used. If you plan on using SLIP,
refer to the application programming guide for your specific package.
AT Command Set Support
The terminal device, (Mobile Application Subsystem), does not have to
support the Attention (AT) command set directly to operate with the
DART 200. Even in cases where the device does support the basic AT
command set, there are some extensions to the command set that are not
supported. Usually, a programmable device can create a constant string
that represents the desired AT command. Sending such a character string
to the DART 200 works the same as sending the AT command.
If the remote device is of limited intelligence it does not need to support
the AT command set at all. The modem can be pre-initialized to work
with the remote device, including being in auto answer mode. In auto
answer mode, when the modem receives a connection request (TCP
mode), or a datagram (UDP mode), it goes online and passes data to the
attached device, just like a wire-line modem. In this situation, the fact
that CDPD is the communications medium is transparent to the remote
device.
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Device drivers
The DART 200 requires no special device drivers. Serial
communications port support provided by the PC Operating System is all
that is needed. For modem setup any ASCII terminal emulator, such as
Terminal, Hyperterminal, Procomm, Kermit, and so on, is appropriate.
For applications use the normal communications port I/O commands
supported by the programming language you use.
Application program structure
A CDPD application is similar in general structure to most network
based applications. It consists of the following major sections:
DART setup
This is usually done before the DART 200 is put into use, or as a special,
first time only function of the application. The needs of the application
and the terminal are evaluated based on the protocol being used (TCP,
UDP, or SLIP mode) and the appropriate options are chosen. Refer to
Chapter 5, DART Supported Protocols, for modem setup samples.
Network connection
Establishing a network connection involves, enabling the Personal
Identification Number (PIN) (if used), registering the modem with the
network (if not set up to register automatically), then establishing the
communication session with a peer device, as follows:
1. If PINs are used, issue the PIN enabling command (AT*E) before
attempting to access the network.
2. For application use (as opposed to testing), set up the modem
registration as fully automatic, by setting the Registration time-out
S-Register to 0 (ATS13=0), then issue an AT\R4 command, as
described in Automatic registration, p. 8-6. Save your changes with
an AT&W.
This causes the DART 200 to automatically register at power up, and
when registration is dropped, for example, due to a power failure or
driving out of the coverage area.
3. A session is established for a client by dialing (ATDn command) to
establish a logical connection with another device (TCP), or to set up
the target device’s IP Address and port for insertion into the data
packets to follow (UDP). Refer to the D command in Appendix F,
DART AT Command Set, for more information.
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4. For a modem functioning as a server, (answering calls or being
polled) activate the appropriate server, TCP (with AT*A1) or UDP
(with AT*A2). The connection can be established automatically by
having auto answer active (S-Register 0 =1), or manually by issuing
an ATA command when the RING message occurs, as described in
Auto Answer setup, p. 8-11.
For both client and server systems, successful completion of the Dial
command (ATD) is indicated by a CONNECT message (verbose mode)
or a 1 (terse mode). This puts the modem in online mode. In this state,
AT commands are ignored, the autobaud function is suppressed, and
flow control (if specified) is enabled.
Data transfer
To accomplish data transfer, the DART 200 must be in online mode.
Data transfer is performed by the Mobile Application Subsystem (MAS)
by sending data to or reading data from the DART 200’s RS-232 serial
port. Unlike the previous activities, data transfer uses device-specific
rather than AT commands. For a PC the I/O commands are directed to
the serial port and use the serial port I/O driver supplied by the operating
system being used.
Outgoing data accumulates in the DART 200 until a data forwarding
condition is reached. The DART 200 then attaches the appropriate
header information, and sends the data onto the CDPD network for
forwarding through the appropriate routers to the target IP Address and
port. Refer to Data forwarding, p. 8-8, for more details.
The incoming packet is received by the DART 200, and the header is
removed, and the data passed, subject to flow control considerations, as
described on p. 8-12, to the attached device.
Modes of operation
A major difference between a Cellular Digital Packet Data (CDPD)
Hayes-compatible network session and a typical synchronous
communications session is the two modes of operation: command mode
and online (data) mode.
AT commands are issued and responded to by the DART 200 when in
command mode. Once a remote station is dialed, or SLIP mode is
started, the modem enters online mode and only transmits or receives
data; it no longer responds to AT commands.
To return to command mode, to process AT commands for error
recovery purposes or to hang up at the end of a session, the DART 200
issues an escape sequence, or drops Data Terminal Ready (DTR) (if
possible) with an &Dn set up option specified. Refer to Escaping
through the control interface, p. 8-16 for details.
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Error recovery
Good application design includes provisions for handling errors. Insert
code to perform the error-handling function after every operation where
an error might occur, such as after every AT command, where the most
likely failure is modem power loss, and after every communications
operation where these five distinct errors are possible:
1. Loss of modem power.
2. Loss of radio signal.
3. Loss of network registration.
4. Loss of host connection (does not apply to UDP).
5. Loss of online mode (a power reset has occurred).
Failure of a communications operation (usually send or receive) is
indicated by:
·
Send - A time out or an error response
Receive - A time out
·
If the MAS is capable of sensing signal status over the RS-232 interface
then testing for loss of signal, registration, or connection can be done (if
desired) before attempting the send/receive operation. If it is not (or the
application designer chooses not to sense prior to I/O operations), then
testing follows failures only.
There is no specific test for loss of modem power. If the modem is in
online mode, and the application does not get an OK or 0 response to the
escape sequence, then power loss can be assumed. Similarly, if the
modem is in command mode and the application fails to get the expected
response to an AT command, then power loss can be assumed.
Status information and error codes, to be analyzed to determine
appropriate error recovery actions, can be obtained from the Data Set
Ready (DSR) and Data Carrier Detect (DCD) signals, or from Status
(S-)Registers 56, 57, 62, 63, 101, 102 and 126. The use of DSR and DCD
for basic status sensing is recommended (if the MAS supports it) for both
speed and simplicity. The available information, by source, is
summarized below.
·
DCD - This signal can be set up at modem initialization time to
follow the state of the connection established condition (&C1), the
state of the RF in range condition (&C3), or the modem’s
registration state (&C4). The default is &C1
·
DSR - This signal can be set up at modem initialization time to
follow the state of the connection established condition (&S1), the
state of the RF in range condition (&S2), or the modem’s registration
state (&S3). The default is &S0 (always active)
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With three variables and only two signal lines, decide which two of
the three items are most crucial to the application. Usually, RF in
range and registration state are tracked. If both of these statuses are
present, then a Dial command (ATD) can be issued. To determine
more than two items of status the MAS escapes to command mode
and reads the network status register (S-Register 57).
·
DTR (Data Terminal Ready) - Transitioning this signal lets the
application enter command mode without having to use the escape
sequence. To do this, the &D1 (escape) or &D2 (escape and
hang-up) option must be selected at initialization time. If this option
is used DTR must be held in the down state for a minimum of 15 ms.
Refer to Escaping through the control interface, p. 8-16, for more
information. The default is &D0 (ignore DTR)
·
S-Register 56 (extended network error codes) - Indicates reasons for
a registration failure. Codes 1-7 are suggested in the CDPD
specifications but may not be followed by all carriers or
infrastructure providers.
1
Registration denied - Network Entity Identifier (NEI) may
be in use by another device
2
Service currently not available
3
Invalid NEI (IP Address)
4
Insufficient authentication credentials
5
6
Authentication credentials not supported
NEI has exceeded usage limitations
7
250
Service denied on this subnetwork; try an alternate Provider
Timed out waiting for home Mobile Data Intermediate
Station (MDIS) registration response
251
252
254
255
Mobile Data Link Protocol (MDLP) parameters unsupported
MDLP version unsupported
Could not access the CDPD network
Could not de-register the NEI because it was not registered
·
·
·
S-Register 57 (network status) - A bit-mapped register showing
several items of interest. For error-handling the values of interest are:
·
·
·
RF in range - value of 128 or greater (bit 7)
Registered - odd value (bit 0)
Connected - value of 133, 165, 197 or 229 (bit 2 and not bit 3)
S-Register 62 (connection failure) - This register indicates at what
point in the operation the connection failed
1
2
3
During the connection process
During the transmission of a packet
During the reception of a packet
S-Register 63 (connection failure) - This register indicates the most
probable cause for the connection failure or loss of connection
24 No socket available
67 Address already in use
69 Network is down
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70 Network is unreachable
71 Network dropped connection or reset
72 Software caused connection abort
73 Connection reset by peer
75 Socket is already connected
76 Socket is not connected
78 Connection timed out
79 Connection refused (for DART to DART the server function is
not active or is of the wrong type)
81 Host is down
82 Host is unreachable
·
S-Register 101 (CDPD available flag) - Indicates not only if the
modem acquired a channel, but also whether it established (or
reestablished) CDPD communications with the MDIS. This is a
better indicator than the RF in range bit found in S-Register 57
0
1
CDPD not available
CDPD available
·
·
S-Register 102 (mean Receive Signal Strength Indication for
acquired channel) - Indicates the RF signal strength in dBm for the
active channel. If CDPD is not currently available (S-Register 101 =
0), this value has no meaning
A negative value usually in the range of -50 to -113dBm. Values
below -100 are unreliable, and below -110 cannot be used.
S-Register 126 (Registration progress status) - Indicates how far
through the registration process the modem proceeded
0
1
2
Protocol not active
Temporary Equipment Identifier (TEI) assignment pending
Link connection establishment pending - waiting for
Unnumbered Acknowledgement (UA)
Encryption key exchange pending - waiting for MDIS Key
Exchange (IKE)
Registration pending - waiting for Intermediate System
Confirmation (ISC)
Registration complete
3
4
5
Use the ATSn? command to read the S-Registers with the modem in
command mode
After sensing the appropriate registers, if the MAS determines it
needs to go back to online mode, it issues an ATO command (TCP
or UDP), or AT*S command (SLIP) to do so.
Automatic registration
Before the DART 200 can operate on the CDPD network it must be
registered. Registration is controlled by the AT\Rn command; the
following options are available:
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·
Manual registration
·
·
·
Automatic registration at power-on
Automatic registration whenever the modem is not registered
Automatic registration when connection originates
These options are described in detail after Registration Timer.
Registration timer
S-Register 13 is the timing register (default 60 seconds) used in
conjunction with the registration function. For manual operation set this
register to a value in the range of 20 to 30 seconds. If the registration
does not take place within the time period specified in this register, an
error returns. The impact of the timer varies depending on the
registration approach taken.
Manual registration
This option allows either the user or the MAS to control exactly when
the registration will occur. It is implemented by the AT/R1 command.
After issuing an AT\R1 command, the AT command processor is
blocked and the modem does not respond to any AT commands, until the
registration completes successfully or the timer expires.
Since waiting to try another command can be very frustrating, large timer
values (above 60 seconds) are not recommended. Limit manual
registration by AT\R1 to testing situations, and then with the timer value
set in the 20 to 30 second range.
Auto-Registration at power-on
Auto-Registration at power-on lets the DART 200 register itself at
power-on time after acquiring a channel, eliminating the need to execute
an AT\R1 command. The function is set up by the AT\R4 command
which turns on bit 5 (value = 32) of S-Register 57, and by letting
S-Register 13 default to 60 seconds.
After executing these commands, the settings should be saved by an
AT&W command. This feature can be deactivated by the AT\R5
command. The AT command processor is not blocked when this type of
registration is in process.
This function is not the complete answer to automatic registration since
the timer might expire before registration is successful. Also, in instances
where registration is lost due to loss of radio signal, such as in a mobile
application, the register at power-on option is useless unless the modem
can be power cycled.
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Auto-Registration when not registered
This function is the same as Auto-Registration at power-on, except that
in addition to executing AT\R4 command, the timer value is set to zero.
This causes the modem to auto register at power-on, and also when it
loses registration. Setting S-Register 13 to zero with an ATS13 = 0
command suppresses the time-out function, and causes the registration
attempt to go on until it is successful.
CAUTION:
If the timer is set to 0,
and a manual
registration (AT\R1) is
tried and fails to
complete, the registration
attempt never times out.
The DART requires a
power cycle to clear this
condition.
This type of registration does not block the AT command interface so
other commands can be executed when auto-registration is in progress.
After making and saving this setting with an AT&W, power cycle or
restart the DART 200 by an AT-R to activate the function.
Auto-Registration/De-Registration at connection/disconnection
This function minimizes the time a modem is registered on the network
by linking registration to connection establishment and de-registration to
connection hang-up. This option can only be used with protocols that
establish point-to-point sessions, such as TCP and telnet, and then only
with client systems; a server must always be registered for connection
requests to be directed to it.
?
NOTE:
This function was
conceived by the CDPD
specification writers
when it was anticipated
that some carriers would
charge for the time an
M-ES was registered on
the network. However,
since no carriers plan on
charging for registration
time this feature is of
little practical use.
This feature is activated by the AT\R2 command which turns on bit 4
(value = 16) of S-Register 57, and must be followed by an AT&W
command to save the setting. This feature can be deactivated by the
AT\R3 command.
Deregistration
The DART 200 can be de-registered at any time by executing the AT\R0
command; however, doing this deactivates the auto-registration feature
of the AT\R4 command until the modem is power cycled, or restarted
with an AT-R command.
In addition, this option
slows down operations
and generates extra
traffic by requiring
registration protocol to be
executed by the modem
every time a Dial or a
Hang-up command is
issued.
Data forwarding
Data forwarding is the process that causes data sent from the MAS
(remote terminal) to the DART 200 to transmit over the CDPD network.
Data forwarding is operational only in TCP, UDP, and telnet modes.
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Manual transmit control
This feature (AT\Mn) controls the recognition of data forwarding
characters in the data stream by the packet assembler when in online
mode. If enabled, the DART 200 recognizes the receipt of either of two
data forwarding characters from the MAS as a condition to transmit the
data in the packet buffer. Any data following the data forwarding
character is not included in the current data packet, but is held over for
the next transmission.
The \Fn command specifies whether or not either, or both, of the data
forwarding characters are included in the data packet. These characters
are specified in S-Registers 51 and 52. The default value for S-Register
51 is 13 <CR>, and for S-Register 52 is 26 <SUB>; these values can be
changed by the end-user. The default for \Fn is \F3; include both
characters in the packet.
If manual transmit control is disabled, the data forwarding characters are
included in the data packet regardless of the setting of the \Fn command.
The DART 200 factory default is Manual Transmit Control disabled
(\M0).
Automatic transmit control
This feature controls the use of the inter-character time-out data
forwarding operation of the packet assembler when in online mode. The
inter-character timer determines the amount of time (idle time) allowed
between characters received from the MAS. The time out value is
specified in S-Register 50 in 1/10 second increments; the default value is
20 (2 seconds). For optimum performance set this value as small as
possible, values of 1 (100 ms) or 2 (200 ms) are commonly used
CAUTION:
Automatic transmit
control must be used
with binary data since it
is not dependent on
data stream content.
The time-out period can be viewed as either the maximum time
permitted between two characters for them to appear in the same packet,
or the wait time after the last character is put in the buffer until the
packet is transmitted. Automatic transmit control must be used with
binary data since it is not dependent on data stream content.
This feature is controlled by the AT\Tn command. The DART 200
factory default is Automatic Transmit Control enabled (\T1).
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Maximum packet size transmit control
This feature is not under end-user control. It causes the data buffer to be
transmitted if the maximum packet size is reached and the conditions
covered by either, or both, of the above features are not met, for
example, if the packet is very large. It is also a backup if both of the
above features are inadvertently disabled. The maximum packet size for
the DART 200 is 1924 bytes (characters) and is not user adjustable. Use
of this technique as the primary data forwarding method is not
recommended.
The maximum physical size of an IP transmission packet is referred to as
the maximum transmission unit (MTU). To avoid packet segmentation,
the maximum segment size (MSS) for a data packet should be the MTU
size less the packet header size. The standard header sizes are 40 bytes
for TCP and 28 bytes for UDP. The following network parameters also
need be considered:
·
Largest MTU size - usually at the host LAN and is defined by the
Ethernet which has an MTU of 1500 bytes and an MSS of 1460
bytes
·
·
Smallest MTU size - usually found at an intermediate router. IP
standards require that network routers support a minimum MTU of
576 bytes. In most cases, this will be the limiting factor
Largest MSS - determined by the smallest MTU found at the various
routing points along the path taken by the packet. Usually, this is 576
minus the packet header size
Based on the above, the largest TCP packet which will avoid
segmentation is 536 bytes; for UDP it is 548 bytes.
Any end-user data packets exceeding the MSS for the network are
fragmented by the network software at one end and rebuilt at the other.
This is transparent to the application, but adds to the transmission time.
However, if any of the fragments are lost the entire MSS, not just the
dropped fragment, must be retransmitted. TCP and telnet (both
TCP-based) do this automatically. For UDP, however; this problem must
be detected and corrected by the application.
There is no method defined for IP to determine the minimum segment
size between two endpoints. Even if one could be developed, the
dynamic nature of IP routing makes it very likely that this value would
fluctuate and not be dependable. Therefore, to ensure the best application
performance use manual or timed data forwarding, and the data packet
sizes suggested above.
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Escape transmit control
A default feature of the modem causing any data remaining in the packet
buffer to be transmitted before the modem returns to command mode.
The escape can be performed by the three-character escape sequence, or
by transitioning DTR with &D1 or &D2 specified. If your transmission
consists of a single packet, this technique can be used to forward the
data.
Usage considerations (for TCP and UDP)
?
Manual transmit control is appropriate if the data packets being built by
the MAS contain character data and always end with one or the other of
two characters (S-Registers 51 and 52). However, if the application
generates variable ending characters, such as a checksum after a data
block, or if it uses a variety of single byte control characters, such as
ACK, NAK, ENQ, EOT, and so on, manual transmit control is not
possible.
NOTE:
This topic has already
been covered for telnet,
and does not apply to
SLIP mode since data
forwarding is a function
of the TCP/IP stack
software employed by the
user.
Automatic transmit control is appropriate for binary data, and also for
character data where the last, or only character sent is variable. This
mode causes the data to be transmitted regardless of what that character
is. However, the default for the intercharacter time-out (ICT) is 2
seconds. In most applications, waiting 2 seconds before sending data
could cause performance problems. Set the ICT (S-Register 50) to a
small (or minimum) value to avoid this timing issue.
Automatic transmit mode must be used if the information being sent is
binary as opposed to character data. Since an 8-bit binary data field can
represent any value from 0 to 255, it is possible that some legitimate data
could appear as one of the data forwarding characters. If manual data
forwarding is used, the data block would be transmitted prematurely,
potentially causing errors and erroneous operation.
Auto answer setup
The DART 200 can be set up to accept incoming connection requests,
either automatically (recommended) or with the ATA command:
1. A server must be active: in TCP use AT*A1 to activate the server
function; in UDP use AT*A2.
?
NOTE:
Auto answer is disabled
while DTR is inactive if
&D1 or &D2 have been
specified.
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2. To use the ATA method, the MAS must have a device. Read
command is pending on the COM port and issues an ATA command
in response to the incoming Ring.
OR
S-Register 0 = 1 enables the DART 200 to remain permanently in
auto answer mode; making call answering fully automatic
(recommended, especially) when dealing with low intelligence
terminals not capable of issuing an ATA command.
3. To answer automatically set S-Register 0=1 enabling the DART to
remain permanently in auto answer mode; making call answering
fully automatic. This is the recommended method, especially when
dealing with low intelligence terminals not capable of issuing an
ATA command.
4. Completion of call establishment at the server in both TCP and UDP
modes of operation is indicated by a CONNECT message (verbose
mode) or 1 response (terse mode). This response can be suppressed,
if necessary, by putting the modem in Quiet Mode (ATQ1).
To set up the DART 200 server for auto answer, use the following
commands:
1. AT*An to activate the appropriate server (1 for TCP, 2 for UDP).
2. ATS0=1 to enable auto answer.
3. AT*Ln to set the listening port. Set the port number in the range
1025 to 4999 (default listening port is 2100 for backward
compatibility and can be left unchanged).
4. AT&W to save settings.
5. Incoming connection requests must reference the listening port. For
example, a TCP establishment request from another DART would be
ATDTn.n.n.n/2100.
This information applies for calls between DARTs, or for calls to a
DART when operating in TCP, UDP, or telnet modes of operation.
Flow control considerations
Flow control is used by a device receiving data over the RS-232 interface
to prevent the transmitting device from sending data faster than the
receiver can process it. The DART 200 supports hardware flow control,
Request to Send (RTS)/Clear to Send (CTS), and Software flow control,
XON/XOFF.
?
NOTE:
Flow control is only
active when in online
mode.
The DART 200 also operates without flow control, leaving you to ensure
that data overruns do not occur. This feature is specified by the \Qn
option; the default is \Q2 Hardware Flow Control.
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DART 200 CDPD Modem User’s Guide
8 Application Programming
Flow control and the new end-user
Flow control often causes problems when applications are first online.
Flow control is not operational when the modem is in command mode
and not interacting with the CDPD network. Since an end-user’s initial
experience with the DART 200 is normally in command mode, it is not
unusual for them to experience a flow control caused modem lockup
when first using online functions, such as registration or ping.
Since the default for this feature is Hardware Flow Control (\Q2), an
attached device that does not support flow control, or a communications
cable with a missing or broken RTS lead will cause a modem lockup.
The modem cannot transfer data and becomes locked until it sees an RTS
signal from the attached device. It remains in the locked state waiting for
RTS until the modem is power cycled.
To avoid this problem check that the attached device and the modem
have matching flow control settings, and that a communications cable
has all the leads needed by the DART 200 present and in working order.
Otherwise, set the modem for no flow control (\Q0).
Flow control in application (online) mode
The purpose of flow control is to prevent buffer overrun in both the
DART 200 and the MAS. The DART 200 has a 256-byte Interrupt
Service Routine (ISR) buffer and a 6K packet buffer, while the MAS
buffer size is application or device dependent. Most MAS devices are
faster than the modem so flow control is normally only a potential
concern for the DART. If the maximum data transfer from the MAS is
less than the 256 byte ISR buffer size, then flow control is not needed
(\Q0).
Some MAS devices have small buffers or insufficient intelligence to
support hardware or software flow control; for those cases, specify the no
flow control option (\Q0). Also, avoid or detect possible buffer overruns
and request retransmission of the data.
For situations not in the above categories, then hardware (\Q2) or
software (\Q1) flow control can be used. However, if transferring binary
(non-character) data is anticipated, only use hardware or no flow control.
Binary data transfer is incompatible with software flow control, because
in a binary data stream any byte can inadvertently have the same bit
configuration as the XON or XOFF control characters. In addition to the
device receiving unexpected and unwanted flow control, the data
character is stripped from the data stream, causing unpredictable results.
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DART 200 CDPD Modem User’s Guide
8 Application Programming
Hardware flow control operation
The DART 200 communicates with the MAS using the CTS lead
(modem controlled) when receiving data, and sensing the RTS lead
(MAS controlled) when sending data.
When the modem receives data from the MAS it holds the CTS line in
the ON state and only transitions it to the OFF condition to exert flow
control (stop data transmission from the MAS).
When the modem sends data to the MAS it monitors the RTS lead from
the MAS; sending data only when RTS is ON, and stopping when the
MAS exerts flow control (wants to stop data transmission from the
modem) by transitioning RTS to the OFF condition. If Hardware Flow
Control is specified, the modem does not begin data transfer to the MAS
unless RTS is ON.
PAD operating mode
The DART 200 is capable of operating in two modes while transferring
data:
·
Packet Assembler - Disassembler (PAD) mode - When in PAD mode
the internet protocol support is provided by the modem
·
SLIP mode - When in SLIP mode the internet protocols are provided
by a software stack in the attached device, usually a PC
The DART uses PAD mode to provide support for UDP, TCP, and
telnet. The form of the dial command (ATDT or ATDP) specifies to the
modem whether TCP or UDP protocol should be used. However, telnet
is a TCP application; something more than the form of the dial command
is required to inform the modem that it should operate in telnet rather
than straight TCP mode. This function is provided by the \O parameter.
Telnet mode is specified by the \O1 parameter (default setting). When a
telnet session is established the modem will begin a negotiating process
with the host to determine the terminal being emulated, whether local or
remote echo will be used, as well as other operating rules for the session.
In addition, when data transfer starts only printable characters and
control characters will be passed. This mode of operation is not suitable
for any application other than telnet: it is not compatible with telemetry
requirements.
For telemetry the option should be changed to \O0 and saved with the
&W command. However, this causes some potential problems because
the \O parameter also controls the F, \M, and \T settings. Each \O setting
has a preferred setting for F, \M, and \T, which may not be compatible
with the end-user's program. The couplings are shown in Table 8-1.
CAUTION:
Whenever \O is
changed, verify that the
F, \M, and \T settings
are still appropriate for
the application.
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DART 200 CDPD Modem User’s Guide
8 Application Programming
Table 8-1. Telemetry options for PAD Mode
Command Description
Select PAD Mode
\O0
·
·
·
F0
Local echo in online mode
\M1
\T0
Enable manual data forwarding
Disable automatic data forwarding
Select Telnet Mode
\O1
·
·
·
F1
Remote echo in online mode
\M0
\T1
Disable manual data forwarding
Enable automatic data forwarding
After changing \O be sure to verify that the coupled parameters are still
set appropriately.
Data and control interface
The DART 200 uses the following eight leads on the RS-232 interface.
·
Carrier Detect (DCD) - Optional**
Receive Data (RXD) - Required*
Transmit Data (TXD) - Required*
Data Terminal Ready (DTR) - Optional**
Signal ground (GND) - Required*
Data Set Ready (DSR) - Optional**
Request to Send (RTS) - Optional†
Clear to Send (CTS) - Optional†
?
·
·
·
·
·
·
·
NOTE:
In general, do not
design equipment with
less than these basic
eight leads to avoid
potential application
programming
limitations.
*The DART 200 cannot communicate with the attached device without these
three signals. In addition, the DART 200 requires these three signal lines to
accommodate firmware downloads.
** If the MAS device can sense and signal on these lines, use them. If not, they
can be ignored. These lines are used for signaling between the DART 200 and
the (MAS). DCD and DSR pass information from the DART to the MAS, and
DTR is used by the MAS to signal the modem.
† Not required if your MAS does not support flow control (\Q0), or if it uses
software flow control (\Q1). Provides hardware flow control between the DART
and the MAS. This is the default (\Q2) for the DART.
CDPD status sensing
Permits the MAS to determine the following without escaping to
command mode, issuing an ATS57?, and testing for specific bits being
on:
1. Does the modem still have a connection to the host system?
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8 Application Programming
2. Is the modem still registered?
3. Does the modem still have an RF signal available?
The DCD and the DSR lead can be set up with AT commands to cause
those signals to follow certain modem status items, including:
·
DCD Operation
·
·
·
·
&C0 DCD is always active
&C1 DCD tracks the state of the connection (default)
&C3 DCD tracks the state of RF in range
&C4 DCD tracks the state of Registration
·
DSR Operation
·
·
·
·
&S0 DSR is always active (default)
&S1 DSR tracks the state of the connection
&S2 DSR tracks the state of RF in range
&S3 DSR tracks the state of Registration
If you decide to use these RS-232 interface functions, refer to the &C
and &S commands in Appendix F, DART AT Command Set.
Escaping through the control interface
Permits the MAS to put the DART 200 in command mode without using
the standard escape sequence with associated time delays. This can be
done if the MAS has the ability to control the DTR lead.
Using the AT&D1 command sets up the DART 200 to switch to
command mode when it senses an ON to OFF transition of the DTR lead.
Using the AT&D2 command sets up the DART 200 to switch to
command mode and hang up (issue an ATH) when it receives an ON to
OFF transition of the DTR line.
The transition of the DTR lead must last at least 15 ms for the escape to
take effect. This delay in the escape taking effect prevents noise spikes
on the DTR lead from triggering an unwanted escape.
Binary data transfer
Many applications need to transfer numeric rather than character data.
This places some restrictions on certain DART 200 features. These are
reviewed below as they pertain to TCP and UDP. Telnet, while it has a
binary mode, does not lend itself to handling binary data efficiently.
Also, since SLIP implementations require a TCP stack running on the
MAS, any SLIP restrictions on moving binary data are a function of that
program.
Restrictions to observe pertain to flow control and data forwarding. In
addition, all binary data transfers must be done using 8 data bits, and no
parity.
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DART 200 CDPD Modem User’s Guide
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Flow control considerations
Software Flow Control cannot be used. Instead, Hardware Flow Control
(\Q2) (default), or no flow control (\Q0) must be used because in a
binary data stream any byte can inadvertently have the same bit
configuration as the XON or XOFF control characters. In addition to the
device receiving unexpected flow control, the data character is stripped
from the data stream, causing unpredictable application results.
Data forwarding considerations
Manual data forwarding cannot be used. This feature is controlled by the
AT\M command; the default is \M0 (disabled). Use automatic data
forwarding for binary data transfers. This feature is controlled by the
AT\T command; the default is \T1 (enabled). In the automatic data
forwarding mode, data is forwarded based on occurrence of an
intercharacter time-out (ICT). The ICT value, found in S-Register 50, is
measured in 1/10 second increments, and has a default value of 20 (2
seconds). Reduce this value to 1 or 2 if speed of operation is an issue.
As with flow control, the reason for not using manual data forwarding is
that in a binary data stream any byte can inadvertently have the same bit
configuration as the data forwarding characters. This event would cause
an unintended transmission of a partial data block, missing the block
ending BCC if one is being used. Avoid this as it can cause unpredictable
and erroneous results.
Parity considerations
The CDPD system assumes parity to be a local issue between the MAS
and the DART 200’s RS-232 interface; parity is not carried over the
airlink. When transmitting 7-bit data with parity, the most significant bit
of each byte in the packet is set to zero and any parity present in the high
order bit is not transmitted. If this data is received by another DART, and
its RS-232 interface is configured for 7-bit data with parity, any required
parity bits are regenerated for compliance with the interface
specification.
?
NOTE:
This section only
applies to applications
where the F-ES
requires odd or even
parity data, or the MAS
communicates uses odd
or even parity.
In an application with a DART on both ends of the session then, parity is
not an issue. However, if there is a digital interface instead of a modem
at the Fixed End System (F-ES) then parity is not regenerated, possibly
creating a problem. The solution is either to modify the F-ES application
to accept data without parity (preferred), or to develop a bypass at the
MAS end of the session.
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8 Application Programming
Bypassing character parity relies on the fact that the DART passes all
8-bits if operating in 8N1 format, and does not autobaud or check
character formats in online mode. However, it requires that the MAS be
able to dynamically change the character format used; between 7-bit with
parity and 8-bit with no parity.
If the DART 200 operates in server mode (responding to calls):
1. The DART 200 must be pre-initialized for 8N1 data format, or (if
possible) dynamically changed to 8N1 format with an AT&L
command.
2. The modem waits for incoming data using the 8N1 data format.
When the modem answers an incoming call (TCP), or receives a
packet (UDP server), it goes online and the format of the data to and
from the MAS is not checked.
3. The MAS is then able to send or receive 7-bit data with odd or even
parity, which is handled by the modem as 8N1 data so the parity bits
are preserved. However, there is a potential problem if or when, the
MAS returns to command mode to check for errors or to hang up.
Unless it can change its parity to 8N1 it cannot communicate with
the modem. The RS-232 interface leads can sense status, to escape,
or to escape and hang up but other functions cannot be performed.
If the DART 200 operates in client mode (placing calls for service), the
situation is different:
1. The MAS communicates with the DART using 8N1 data in
command mode, up to and including the dial command.
2. The MAS then switches to the required 7-bit data plus parity for
communicating with the F-ES.
3. At the completion of the session the MAS must switch back to 8N1
data format for command mode communication with the modem. If
the MAS cannot switch data formats, and must use odd or even
parity at all times, it can only function as a server device.
PAD keep-alive considerations
Keep-alives provide the means for a TCP application in the MAS to deal
gracefully with time-out conditions or software crashes.
·
In transmit mode, it allows the DART 200 to generate session
keep-alive characters if the MAS is slow to provide data to transmit
·
In receive mode, it provides a time-out to allow the application to
terminate a session in an orderly fashion, if the F-ES does not send
data or a keep-alive character within a end-user specified time-out
period
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Shutting down a CDPD session in an orderly fashion after an abnormal
termination at the F-ES side of the session, eliminates the possibility of
the DART 200 having a half open TCP/IP connection, which usually
requires a power cycle to clear. This can be a serious problem if the
DART is in a remote location. The default for this feature is not enabled
(*K0).
This facility works in transmit only mode, receive only mode, or in both
modes. It uses a keep-alive character (S-Register 85) and a keep-alive
time-out (S-Register 86) to implement the function. The timer restarts
when data is sent or received. The default value for the keep-alive
character is binary 0 with an allowable range of 0 to 255, and the
time-out period default is 120 minutes with an allowable range of 1 to
255.
Timer expiry in transmit mode
If the timer expires in transmit (or transmit/receive) mode, pending data
or the keep-alive character is forwarded. This ensures that the receiving
session does not time out. For a half open connection (the other end
terminated abnormally) this transmission eventually causes the
connection to close, because the other end cannot acknowledge receipt of
the data packet or the keep-alive character.
Timer expiry in receive mode
In receive (or transmit/receive) mode, incoming keep-alive packets are
discarded if the incoming keep-alive character matches the value in
S-Register 85. If the timer expires in this mode, meaning no data or
keep-alive character was received within the timeout period, an escape is
performed and an ATH command is issued to close the connection. This
leaves the DART 200 ready to receive another incoming connection
request.
Timer expiry for keep-alives
For one way keep-alives (transmit only at one end and receive only at the
other) set the transmit time-out value as less than the receive time-out
value to ensure proper operation. For keep-alives in both directions
(transmit/receive) set the time-out values at each end as equal.
?
NOTE:
The keep-alive
algorithm has a small
amount of hysteresis
built in to cause the
transmit time-out to
occur ahead of the
receive time-out to
maintain the link.
The most common use of this feature is with an unattended MAS, where
the modem is set up with the receive keep-alive option specified (*K2)
and S-Register 86 set in the 3 to 5 minute range. This permits the modem
to break the session, if the central site crashes, and be ready for another
call without manual intervention when the central site restarts.
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DART 200 CDPD Modem User’s Guide
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Escape sequence considerations
The escape sequence is one of two ways the MAS forces the DART 200
to leave online or SLIP mode and return to command mode. The other is
to drop the DTR line, as described in Escaping through the control
interface, p. 8-16.
Leaving online or SLIP mode is required for the DART 200 to respond
to AT commands. Commonly, this occurs at the completion of a session
to terminate the connection (hang up) with the ATHn command.
Another common reason is to interrogate modem status for local radio
resource conditions, or for error recovery operations.
CAUTION:
Do not reduce the guard
time to zero, because this
exposes the application to
an unwanted escape if
three successive escape
characters inadvertently
appear in the data
stream. Leave the guard
time as larger than the
expected inter-character
time in the MAS to
The DART 200 escape sequence consists of three escape characters (E)
and a 1-second guard time (G). Unlike standard Hayes-compatible
modems that use a GEEEG escape sequence, the DART 200 uses an
EGEGE sequence. Whether or not the escape characters are passed onto
the network as data (&E1) or filtered from the output data stream (&E2)
can be specified.
modem data transfer.
Each unit of guard time
is approximately 20
milliseconds.
Escape code recognition controls whether or not the DART 200 responds
to the escape code. The default is &E1 (recognition enabled and the
escape sequence is passed to the network). For manual operation this
feature must be enabled (&E1 or &E2). For application use it can be
disabled (&E0) if the MAS can control the DTR lead in the RS-232
interface. However; even in this case, the &E0 option is not
recommended as the inability to escape manually it can limit debugging
capability.
The escape character (+) is in S-Register 2 and the guard time (50 in
units of 1/50 second) is in S-Register 12: both can be changed at set up
time or under application control. There is no obvious reason to change
the escape character, but it can be desirable in interactive applications to
reduce the guard time from its 1-second default value to improve
application responsiveness.
Command response options
?
There are three setup options controlling if, and how result codes are
presented to the MAS:
NOTE:
Terse mode only applies
to command responses
(such as AT). Register
or modem status
inquiries (such as
ATS57?) will still
provide a response
which is bracketed by
both carriage return
<CR> and linefeed
<LF> characters.
·
Quiet Mode (Qn) - Controls whether or not result codes are returned
to the MAS. The default value is enabled (Q0). There are few
situations where an application can operate without seeing return
codes. However, some non-intelligent devices can be attached to the
DART 200, that do not expect anything but poll characters; in that
situation Quiet Mode enabled (Q1) is appropriate. Use the default
(Q0) except in these special situations
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·
Verbose Mode (Vn) - Controls whether the DART 200’s command
responses are textual or numeric. The default is enabled (V1). This is
recommended for manual interaction with the DART 200, such as
initial setup. The verbose response consists of a text string preceded
and followed by a <CR>/<LF>. Terse responses consist of a numeric
response code followed by a <CR> only. Terse responses are
appropriate for application use. For a complete listing of the response
codes, see Messages and response codes, p. 8-25
·
Extended Result Codes (Xn) - Determine whether or not all return
codes are enabled. The default is enabled (X1). If disabled (X0), only
return codes 0-4 or corresponding verbose counterparts are enabled.
In that case, return codes of five and above are mapped onto codes 0
to 4 as appropriate. It is generally not desirable to disable this feature
Echo option selection
Echo lets data being keyed in on the keyboard of an ASCII terminal
attached to a computer (either local or remote) appear on the terminal
screen (the computer echoes the characters back to the screen). To speed
up the process, or to reduce wireless data traffic, the echo function can
optionally be done by the modem. The DART 200 provides two echo
options: command mode and online mode.
The default for command mode echo is enabled (E1). This feature causes
all AT commands to be echoed by the modem. This feature is very useful
for manual operation. However, when an application is in command
mode the echoes are a nuisance to be discarded when searching for the
command response; for application use disable this option (E0). In
development using both modes, echo can be enabled by end-users and
application disabled at initialization.
The default for online mode echo is do not echo characters locally (F1).
This implies that the remote device has the option of echoing the online
data stream. The only time this capability is useful and could happen is
during a telnet session. In a typical M-ES to F-ES CDPD transaction or
data transfer application using UDP or TCP, no echoing is needed or
desired. Use the default (F1) to suppress local echoing of the online data
for all applications. If this is not done and online echo is active (F0), all
data sent by the attached device is echoed back to it by the modem that
can complicate application programming; or, in the case of
non-intelligent devices, can cause unpredictable operation.
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Channel acquisition restrictions
This feature of the modem limits the RF channels available for modem
use. It is controlled by the AT\Jn command; one of the modem’s profile
parameters. If activated, this feature limits the modem to using channels
where a channel identifier, such as a service provider ID (SPI), service
provider network ID (SPNI), wide area service ID (WASI), local service
area ID (LSAI), or various combinations of these, matches values
previously stored in the DART 200 with AT^H (SPI), AT^I (SPNI)
and/or AT^L (WASI or LSAI) commands. The options available vary
depending on the CDPD version used. Refer to the \J command in
Appendix F, DART AT Commands, for more information.
?
If a \N0 command is
entered, which
NOTE:
frequently happens
when a new user
inadvertently enters an
illegal AT\N?
command, it forces
home only mode; a
combination of \J1 and
\N0. This prevents
channel acquisition
unless a WASI or LASI
is entered or \J is reset
The values for SPI, SPNI, and WASI or LSAI stored by the end-user can
be viewed by AT^H?, AT^I?, and AT^L? commands. View the values
for these items being broadcast by the network with the AT&V+
command. The WASI or LSAI is found in S-Register 107, the SPNI in
S-Register 108, and the SPI in S-Register 114 (CDPD 1.1 mode only).
Restrict channel acquisition by making one or more entries for SPI,
SPNI, and WASI and then activating the feature with an appropriate \Jn
setting. When this feature is activated, the DART 200 cannot acquire a
channel unless the identifier specified by the \Jn choice matches those
being broadcast by the carrier; usually, only a single restriction is applied
(\J1, \J2, or \J3).
Multiple item restrictions (\J4 through \J7) let the end-user be more
creative for special applications. Multiple entries of a specific type (SPI,
SPNI, or WASI) are logically OR’d, and entries of different types are
logically AND’d. For example, if two SPNIs are entered, the channel is
acquired if either SPNI was found. If a SPNI and a WASI are entered the
channel is acquired only if both were found.
The default value for \J is no channel acquisition restrictions (0).
Baud considerations
The DART 200’s default communications port settings are 9600 baud,
with 8 data bits, no parity, and 1 stop bit with autobaud active. The
autobaud feature allows the DART 200 to sense speed and data format of
attached devices and adjust accordingly. The DART 200 does this by
keying on the leading A (upper- or lowercase) of an AT command; other
leading characters do not trigger the autobaud feature. Autobaud is active
in command mode only.
?
Autobaud is active in
command only.
NOTE:
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If the DART 200 is attached to a device that operates at a different speed
or data format, an appropriate AT&L command, followed by an AT&W
(to save the change) must be issued. Executing the AT&L command
disables autobaud and fixes (locks) the DART 200 to settings in the
AT&L command. Available bauds are 300, 1200, 2400, 4800, 9600, and
19.2K. Regardless of the baud selected for the communications port, the
CDPD airlink speed is fixed at 19,200 bps.
Autobaud can be reactivated with an AT&L1 command.
Maximum block size considerations
To maximize data throughput, most communications application
designers use the maximum blocksize compatible with good
performance. On land lines this number is usually 1024 bytes or larger. If
data blocks are too large, the likelihood of one dropping bits and having
to retransmit increases. If this occurs, the overall message transmission
times increase proportionately. If blocks are too small, the likelihood of
dropping bits is much smaller, but delays associated with transmitting
many more blocks increases overall transmission time. Better quality
lines decrease the likelihood of dropping bits, and faster lines decrease
delay times; however, the tradeoff always remains.
In a wireless environment the same tradeoffs apply. However, the speed
and quality is not high by landline standards, so maximum blocksizes are
necessarily smaller. The real advantage of wireless is simply in being
wireless.
Another consideration in the CDPD environment, is that there is a charge
for the number of bytes transferred. Since the headers are a fixed size and
relatively large (40 for TCP, 28 for UDP), there is customer pressure to
minimize the number of blocks (make them larger) to reduce the cost.
This can be self-defeating because larger blocks increase the likelihood
of occasionally retransmitting a large block. Again, what is gained by
having fewer blocks is lost by retransmitting some of them due to the
increased likelihood of errors.
Data packets above 536 bytes are likely to be fragmented; a process that
on average adds to the overhead associated with larger blocks. Refer to
Maximum packet size transmit control, p. 8-9, for a discussion of
problems resulting from a packet size that was too large.
Start with a blocksize of 256 bytes. However, this parameter is a function
of both the application and the local CDPD environment. To optimize
data transfer a trial and error approach varying the blocksize is
recommended, for example:
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8 Application Programming
1. If your application involves transmitting relatively large data files,
test the data transfer using a variety of block sizes. Begin with the
large blocks preferred by your customer. Get some throughput
timings and develop an average. If operating in a sniff-and-hop
CDPD environment, there can be significant variation in the timings.
If CDPD operates on dedicated channels variations are much less.
2. Do enough tests to get a meaningful average. If your application
operates at specific times of the day in a sniff-and-hop environment,
only test during the times the application normally operates.
?
NOTE:
Bigger is not
3. Start dropping the blocksize and repeating the analysis. A plot of
blocksize versus time to complete the file transfer shows a low point
somewhere between the extremes. For example, start with a 1200
byte blocksize, and drop it by 200 until you hit 200. Explore the low
point; the real low might be at 337 bytes, or 489.
necessarily better when
it comes to data transfer
block sizes. Take time to
test and analyze your
situation for optimum
results.
4. Once the best point from a throughput perspective is found, ask your
carrier for a protocol trace of the transfer to determine actual byte
counts. Again, try several, since variations in timing usually imply
variations in byte count. To ensure that the best point also has the
lowest byte counts, trace some tests with larger and smaller
blocksizes.
Modem dial directory
To help minimize entering IP Addresses, which with port numbers can
be quite long, the DART 200 offers a dial directory to store up to 10
entries. Refer to &Z command in Appendix F, DART AT Command Set.
These addresses are referenced by slot number (0 to 9) and can be used
for dialing (ATDTSn or ATDPSn), pinging (AT*PSn), or specifying
friendly IP Addresses for the friends only feature.
?
NOTE:
Entries do not need to
be sequential, and port
numbers are not
required (except for dial
addresses). Also, having
a port number does not
prevent an entry from
being used for pinging
or as a friendly address.
Make entries with the AT&Zn= command, and view the directory with
the AT&Z? command, as shown in Figure 8-1.
Figure 8-1. Viewing the IP Address directory
AT&Z?
&Z0: 166.174.113.27/1200
&Z1: 166.174.44.13
&Z2: 166.174.113.63/2100
&Z3:
&Z4:
&Z5:
&Z6:
&Z7:
&Z8:
&Z9: 166.174.113.31/2100
OK
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8 Application Programming
Entries with port numbers can be used as both ping targets and in the
friends’ list. The port numbers are ignored if not required by the
command or function.
Messages and response codes
The DART 200 provides information to the MAS concerning its
operation by response codes and messages. By default (X1) the modem
presents one of 10 response codes in verbose (textual) or terse (numeric)
format. If extended result codes are disabled (X0), only response codes 0
to 4 are available, codes 5 to 10 are mapped onto codes 0 to 4, as
appropriate. Disabling extended response codes is not recommended.
Terse Verbose
0
OK
CONNECT
RING
?
1
2
3
NOTE:
Error codes 7 and 8 do
not apply to UDP,
because UPD is a
connectionless protocol
with no error feedback.
NO CARRIER - The modem did not have an active CDPD
channel at the time the operation was attempted
ERROR
NO DIALTONE - The modem was not registered at the time the
operation was attempted
4
6
7
8
9
BUSY - Connection is busy or an improper port was specified or
the appropriate server was not active at the target location
NO ANSWER - Auto answer was not enabled, or that the remote
modem is not registered or has lost RF coverage
BLOCKED - PIN Number or Service Provider Key was entered
incorrectly three times, or the Unblocking Key was entered
incorrectly ten times. To clear this condition refer to Appendix F,
Clearing blocked status, p. F-23
10
NOT ENABLED - A command requiring a PIN, or requiring the
modem to be in Service Provider mode was used
Messages
The only standard message that the DART 200 issues is:
INVALID NEI: CONTACT SERVICE PROVIDER
This means that the modem does not have an IP Address (NEI) stored in
it yet, so enter one before starting communications. It does not prevent
the modem from processing AT commands as part of normal modem
setup.
If other messages are encountered, contact modem technical support for
assistance.
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8 Application Programming
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Appendix
A
Limited Warranty and
Service
Limited warranty
Sierra Wireless, Inc. (Sierra Wireless) warrants your DART CDPD
Modem model 200 against all defects in materials and workmanship for
a period of twelve (12) months from the date of shipment, subject to the
following terms and conditions:
The DART 200 Cellular Packet Data Modem (CDPD) is compatible with
both version 1.0 and 1.1 of the CDPD Specification, meeting FCC
requirements for the modem, and is compatible with cellular base
stations as of Feb. 1, 1996. Software upgrades, if needed, including those
required for future compatibility needs are furnished as appropriate.
The sole responsibility of Sierra Wireless under this warranty is limited
to repair or, at the option of Sierra Wireless, replacement of the DART
200 CDPD Modem. There are no express or implied warranties,
including those of fitness for a particular purpose or merchantability, that
extend beyond the face hereof.
SIERRA WIRELESS is not liable for any incidental or consequential
damages arising from the use, misuse, or installation of the DART 200
CDPD Modem.
This warranty does not apply if the serial number was removed or if the
Modem was subjected to physical abuse, improper installation, or
modification.
Service
In the event of equipment malfunction, all repairs should be performed
by Sierra Wireless, Inc. or an authorized agent. It is the responsibility of
users requiring service to report the need for service to Sierra Wireless,
Inc. or to one of its authorized agents.
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DART 200 CDPD Modem User’s Guide
A Limited Warranty and Service
If you are having trouble with your modem, or to obtain warranty service
or out-of warranty repair, please call Sierra Wireless Support
(604.231.1100) between 8:00 am and 5:00 PM Pacific Time. If it is
necessary to return the modem, you will be given an RMA number,
asked to fill out the form shown in Appendix H, and to return it with the
modem, shipped prepaid, to the address shown below. Do not return the
modem without obtaining an RMA number.
Sierra Wireless Inc.
Attention: Technical Support
13151 Vanier Place #260
Richmond, British Columbia
Canada V6V 2J2
RMA Number:_______________
For technical support of third-party applications used with the DART
200, contact the application vendor directly. Sierra Wireless does not
provide support for these applications.
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Appendix
B
Product Specifications
Power requirements
Mobile
11.0 to 16.0 VDC; 13.8 VDC nominal operating voltage, +/- 1.0 V
maximum ripple; maximum current 2.5 A; 3.0 A line fusing required.
Stationary
120 VAC operation with optional UL/CSA approved AC power adapter
Peak
Transmit: 2.5A; Receive: 300 ma
Power cable
Six (6) ft. 20 AWG; Red positive, Black negative. Connector is a Molex
Micro-Fit 3.0 (PN 43025-0200); Pins (2) (PN 43030-0001)
Size
6.3 in x 3.4 in x 1.0 in (16 cm x 8.64 cm x 2.54 cm)
Weight
12 ounces (0.34 kg)
Operating environment
Temperature: -22F to +140F (-30C to +60C)
Humidity:
45 to 75 % relative humidity
RF power output
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DART 200 CDPD Modem User’s Guide
B Product Specifications
3 watts (maximum)
Frequency range
Transmit: 824 to 849 MHz, Receive: 869 to 894 MHz
Data rates
Airlink:
19,200 bits per second, half duplex
Serial interface: 300 to 19,200 bps auto select
Antenna
Standard cellular antenna of good quality with a maximum gain of 3 dB.
Female TNC connection. Snub-nosed (rubber-duck) antenna are not
recommended.
Antenna cable
Low loss, high quality, 50 OHM, coaxial cable, (if required) appropriate
TNC connectors.
Data connection
Serial RS-232; female DB-9 connector
Data cable
Shielded RS-232 serial cable with DB-9 male connector.
Refer to Figure C-2 diagram in Appendix C, Charts and Diagrams.
Protocols
TCP, UDP, and SLIP; telnet via internal TCP/IP stack
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Appendix
C
Charts and Diagrams
Figure C-1 shows the hole pattern for the mounting bracket. Use a 4-40
machine screw, a 4-25 tapping screw, or a 0.125 DIA rivet to fasten the
bracket. A flat washer is not required because the bracket is made of
hardened steel, but a lock washer is required.
Figure C-1. Mounting bracket template
4"
1.8
Figure C-2 shows the modem connector pinout configuration. A straight
cable is required between the DTE (computer or terminal) and the DCE
(modem).
Figure C-2. Modem connector pinout
1 - Carrier Detect (CD)
2 - Received Data (RXD)
3 - Transmitted Data (TXD)
4 - Data Terminal Ready (DTR)
5 - Signal Ground (GND)
6 - Data Set Ready (DSR)
7 - Request To Send (RTS)
8 - Clear To Send (CTS)
9 - N/C
5
4
3
2
1
DB-9S
(on the unit)
9
8
7
6
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DART 200 CDPD Modem User’s Guide
C Charts and Diagrams
The pin functions for pins labeled in Figure C-2 are listed in Table C-1
Table C-1. Pin functions
Pin Number Name
Function
Direction
To DTE
1
2
3
4
DCD
RXD
TXD
DTR
Carrier Detect
Receive Data
Transmit Data
To DTE
From DTE
From DTE
Data Terminal
Ready
5
6
7
8
GND
DSR
RTS
CTS
Signal Ground
Data Set Ready
Request to Send
Clear to Send
Both
To DTE
From DTE
To DTE
Table C-2 lists the RS-232 signal interference specifications.
Table C-2. RS-232 signal interface
Direction
Logical
Voltage Level Load
Status
Condition
Input (From DTE) One
-3 to -25 VDC
5K Ohm OFF, Mark
Zero
+3 to +25 VDC 5K Ohm ON, Space
Output (To DTE) One
-5 to -8 VDC
+5 to +8 VDC
3K Ohm OFF, Mark
3K Ohm ON, Space
Zero
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Appendix
D
SLIP Setup Examples
Trumpet
The Trumpet Winsock is a shareware Windows only package that is
currently in widespread use. Support for it is available primarily through
Internet E-mail and the USENET newsgroup at alt.winsock. Look for a
file called winsock.zip and a set of basic applications (ftp, telnet, ping,
etc.) in a file called winapps.zip at:
ftp.psychol.utas.edu.au:/pub/pc/trumpet/winsock.
Trumpet is frequently used to support the SLIP interface of CDPD
modems including the DART. For the DART the installation and startup
instructions follow. Refer to Chapter 5, DART Supported Protocols, for
complete information on SLIP setup.
?
Installation and startup
NOTE:
These instructions
assume that the
DART SLIP setup
described in Chapter
5 has been completed.
The following discussion assumes that Trumpet is not yet installed on
your PC.
To do a basic installation:
1. Create a directory called Trumpet on your C drive
2. Copy winsock.zip and winapps zip to the TRUMPET directory
3. Unzip the files using PKUNZIP
·
·
PKUNZIP WINSOCK.ZIP
PKUNZIP WINAPPS.ZIP
4. If desired create Icons for TCPMAN, PINGW and TELW
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D SLIP Setup Examples
To set up Trumpet:
1. Start Trumpet from Windows (Icon, or File/Run/TCPMAN).
2. On the Trumpet Winsock Screen, click on File then click on
Setup. The Trumpet setup screen appears:
3. Set IP Address to DART NEI (IP Address).
4. Set Default Gateway to DART SLIP address (1.1.1.2 by
convention). If this field is grayed out, turn off internal SLIP
temporarily to access it.
5. Set MTU to 296 and MSS to 256.
6. Set Timeout = 5.
7. Turn Internal SLIP - ON if it was off.
8. Check that the modem is at the baud rate selected.
9. Turn Van Jacobsen Compression - ON.
- Be sure to specify *C1 on the DART profile.
10. Turn Hardware Handshake - ON.
- Be sure to specify \Q2 on the DART profile.
The rest of the setup fields can be allowed to default.
11. Click on OK to save changes and return to Trumpet Winsock
Screen.
12. On the Trumpet Winsock Screen, click on Dialer then click on
Options.
13. Select No Automatic Login, then click OK to save changes and
return.
14. Exit Trumpet.
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DART 200 CDPD Modem User’s Guide
D SLIP Setup Examples
15. Put the DART into SLIP mode by entering an AT*S command. The
ASCII terminal emulation program being used must be configured
for the same speed as that set for the Trumpet baud rate or SLIP
communication is not possible. (Recommended for first time users.)
OR
Create a startup script for use with the Trumpet Automatic Login
feature: this issues the AT*S and read the OK response.
16. Restart Trumpet to activate the changes. The Trumpet/SLIP interface
is now active. Run your applications with it, including:
·
·
·
Ping
Telnet
Netscape
Windows 95
Windows 95 users have the option of using Microsoft’s built-in software
stack, shareware products like Trumpet, or commercially available
Winsock stacks. To enable use of the Windows 95 built-in stack Sierra
Wireless has developed a DART inf file, a startup script (scp) file, and a
detailed installation procedure for use with Windows 95. The
documentation describes how the DART works with W/95’s Dial Up
Networking support.
To obtain a copy of the DART Windows 95 support contact Sierra
Wireless technical support at 604.231.1100, or visit our web site at:
www.sierrawireless.com
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D SLIP Setup Examples
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Appendix
E
S-Registers
The configuration of the DART is accessible to the Mobile Application
Subsystem (MAS) as a set of parameters known as Status (S)-Registers.
Some registers can be updated directly with AT commands, others are
read-only. The set of registers and modem options (also set with AT
commands) is known as the configuration profile. At least three distinct
profiles are present in the DART, including:
·
Active Profile - Set of register values and options actually used as
the current operational parameters of the modem. Registers can be
queried individually with the ATSn? command, or modified using
the ATSn= command (where n = the S-Register number). The entire
profile, registers and options can be viewed with the AT&V
command
·
Saved Profile - Used at power-up to establish the power-on
configuration state. It is created by the write profile (AT&W)
command, that copies the current active profile into the profile save
area. The saved profile is preserved across cold starts or
power-cycles. The saved profile can be recopied over the active
profile at any time with the soft reset (ATZ) command. Some CDPD
modems (but not the DART) can have more than one saved profile
available for use
·
Factory Profile - An embedded permanent profile that cannot be
modified from the factory default setting. The factory profile can be
copied into the active profile with the load defaults (AT&F)
command.
Register display formats
The S-Registers can be displayed in groupings by use of the AT&V
commands: AT&V for S-Registers 0 through 99, and AT&V+ for
S-Registers 100 through 126. The format of the data displayed by these
two AT&V commands is different. In addition, the format of the data
displayed by the ATSn? command is also different in many cases,
particularly for registers above 100. These variations are summarized
below.
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DART 200 CDPD Modem User’s Guide
E S-Registers
Registers 0 through 99 formats
The AT&V command displays these registers as a group. Each
S-Register is displayed as a three-position numeric field. The ATSn?
command displays these registers individually, as three-digit numeric
fields except for S-Register 53. S-Register 53 always displays as 000 in
the group display, but shows the IP Address and port number of the
client system (if any) in the individual display.
If there is no client, the display is 000.000.000.000. If there is a client,
the format is variable. The general format is n.n.n.n,p where each n
represents one octet of the IP address, and p represents the port number.
However, any leading zeros in any of the IP address octets or the port
number is dropped. The result could be anywhere from 9 to 21 digits in
length.
Registers 100 through 126 formats
The AT&V+ command displays these registers as a group. However, the
group format varies depending on whether the modem is operating in
CDPD V1.0 or V1.1 mode. In CDPD V1.0 mode, all registers display as
4 digit numeric fields except 114, 115, and 116, which display as 7
position fields with a nnn,yyy format. In CDPD V1.1 mode, all registers
are displayed as 4 position numeric fields except 115 and 116, which are
not used or displayed. All register values are decimal except for 111,
117, and 120 through 125, which use hexadecimal (hex) format.
When the ATSn? command displays these registers individually, the
formats range from two to seven digits. The only differences between
CDPD versions is for register 114 which is seven digits for CDPD V1.0,
and four digits for CDPD V1.1, and registers 115 and 116 that do not
display in the &V+ command but shows as seven digits if displayed
individually. Register 111 displays as two hex digits preceded by a 0x,
while 117 and 120 through 126 as four hex digits preceded by a 0x, as
summarized in Table E-1.
Table E-1. S-Register digits
S-Register
100
Digits
S-Register Digits S-Register Digits
4
3
4
2
3
4
4
5
5
109
110
111
112
113
114
115
116
117
4
4
4
4
118
119
120
121
122
123
124
125
126
3
3
6
6
6
6
6
6
3
101
102
103
104
105
106
107
108
4
4 or 7
7
7
6
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DART 200 CDPD Modem User’s Guide
E S-Registers
Register definitions
Figure E-1 shows that in bitmapped registers bit 7 is the high order
(leftmost) bit and bit 0 is the low order (rightmost) bit.
?
NOTE:
Figure E-1. S-Register bit positions
The bitmapped registers
are in the reverse of
some notation systems
in wide use.
S-Register
Bit Position
7
6
5
4
3
2
1
0
Table E-2 summarizes the S-Register set, valid parameter ranges, and
factory default values [n]. S-Registers listings followed by (SM) can
only be accessed when in Service Provider Mode, while those followed
by (RO) are read only and cannot be modified.
Table E-2. Register summary
Register Value
Default Description
S0
0,1
0
Auto answer; enable = 1
S1
0,1
1
Send LF with CR; telnet online
mode only; yes = 1
S2
S3
S4
S5
S6
S7
0..255 ASCII
43 ‘+’
Escape code character
1..127 ASCII 13 <CR> Carriage return character
0..127 ASCII 10 <LF> Line Feed Character
0..127 ASCII
8 <BS>
Backspace character
0..127 ASCII 127<DEL Delete character
0..255
20
ATA command connection
establishment time-out (sec)
S8 (RO)
S9 (RO)
0..255
0..255
250
5
Reserved
Reserved
S10 (RO) 0..255
80
175
50
60
74
Reserved
S11 (RO) 0..255
Reserved
S12
S13
0..255
0..255
Escape code guard time (1/50 sec)
Registration time-out (sec)
Command status
S14 (RO) bitmapped
0
·
·
Online mode echo; see F
command; (default is F0) = 0
Command mode echo; see E
command; (default is E1) = 2
1
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E S-Registers
Table E-2. Register summary (cont.)
Register
S14 (RO)
(cont.)
Value
Default Description
2
3
4
·
Quiet mode; see Q command
(default is Q0) = 0
·
Verbose mode; see V command
(default is V1) = 8
Unused
Escape mode; see &E command
(default is &E2) = 64
·
·
5, 6, 7
S15 (SM)
S16 (SM)
0..255
10
50
RR Cell Change XID SER Threshold
(1/10 = 10%)
0..255
RR Cell Change XID SER Time (in
100 msec increments)
S17 (SM)
S18 (SM)
S19 (SM)
S20 (SM)
0..255
0..255
0..255
0..255
10
10
Reserved
Reserved
151 Reserved
0
LCI to restrict channel access (CDPD
1.1)
S21 (RO)
bitmapped
32
Equipment status
0
·
·
Unused
1,2
DSR operation; see &S
command (default is &S0) = 0
3,4
·
·
DTR operation; see &D
command (default is &D0) = 0
5,6,7
DCD operation; see &C
command (default is &C1) = 32
S22 (RO)
S23 (RO)
bitmapped
0,1, 2, 3
4, 5, 6
16
91
Equipment status
Unused
Extended result codes; see X
command (default is X1) = 16
7
bitmapped
0
Unused
Equipment status
·
Auto SpeedDetect
0 = fixed baud rate
1 = auto baud active (default) = 1
1,2
·
Parity
0 = even
1 = none (default) = 2
2 = odd
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E S-Registers
Table E-2. Register summary (cont.)
Register
S23 (RO)
(cont.)
Value
3,4,5
Default Description
·
Value Baud:
0 = 1200
1 = 2400
2 = 4800
3 = 9600 (default) = 24
4 = 19200
7 = 300
6
7
·
·
Stop Bits:
0=2
1=1 (default) = 64
Data Bits:
1 = 7
0 = 8 (default) = 0
S24 (SM)
0..255
140 RR Direct Hop Acquisition RSSI
Threshold (dBW)
S25 (SM)
S26 (SM)
S27 (SM)
0..255
0..255
0..255
0
3
Reserved
Reserved
140 Lowest spiral search initial acquisition
threshold (V1.0) - dBW
Lowest wide area search initial
acquisition threshold (V 1.1)
S28 (SM)
S29 (SM)
S30 (SM)
S31 (SM)
0..255
0..255
0..255
0..255
140 Lowest intra-area cell transfer spiral
search acq. threshold(dBW)
90
10
10
RR Intra-area Acq. RSSI threshold for
highest start (dBW)
Channel Congested timer (in 500 msec
increments)
Spiral decrement for intra-area cell
channel search (dB)
S32 (SM)
S33 (SM)
S34 (SM)
S35 (SM)
0..255
0..255
0..255
0..255
5
2
1
Symbol update timer (in sec)
Reserved
Reserved
RR Power level Update Time (in 100
msec increments)
65
S36 (SM)
0..255
41
Power Product override value (see bit
7 of SReg60)
S37 (SM)
S38 (SM)
S39 (SM)
0..255
0..255
0..255
7
3
10
Reserved
Reserved
Spiral decrement for initial channel
search (dB)
S40 (SM)
S41 (SM)
0..255
0..255
90
RR initial Acq. RSSI Threshold for
highest start (dBW)
140 RR Undirected Hop Acq RSSI
Threshold (dBW)
S42 (SM)
S43 (SM)
S44 (SM)
0..255
0..255
0..255
80
100 Reserved
23 CDPD 1.0 Cell Change RSSI
Reserved
Threshold XID override (dB)
(Default = value of S44 - 143dBW =
-120 dBW)
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E S-Registers
Table E-2. Register summary (cont.)
Register Value
Default Description
S45 (SM) 0..255
50
Cell Change RSSI time period XID
override (V1.0) (in 0.1sec)
RSSI Average time period XID
override (V1.1) (in 0.1 sec)
Cell Change BLER Threshold XID
override =100/S46 (%) (V1.0)
BLER Threshold XID Override
=100/value of S46 (%) (V1.1)
Cell Change BLER Time period XID
override (V1.0) (in 0.1 sec)
BLER Average time period XID
override (V1.1) (in 0.1 sec)
RR BLER Initial Acq. Threshold (%)
Timer for channel search termination
mode (in 0.5 sec.)
S46 (SM) 0..255
5
S47 (SM) 0..255
50
S48 (SM) 0..255
S49 (SM) 0..255
50
40
S50
0..255
20
Data forwarding idle time-out ( in 1/10
sec.)
S51
S52
0..255 ASCII 13 <CR> Primary data forwarding character
0..255 ASCII 26<ctl-Z> Secondary data forwarding character
S53 (RO) char string
0
IP Address and port number of current
TCP/UDP session partner
Reserved
Reserved
Extended network registration error
codes
S54 (RO)
S55 (RO)
S56 (RO) 0..255
0
0
0
0
1
·
·
No meaning
Registration denied (NEI already
in use)
2
3
4
·
·
·
Service currently unavailable
Invalid NEI (IP Address)
Insufficient authentication
credentials
5
6
7
·
·
·
Unsupported authentication
credentials
NEI has exceeded usage
limitations
Service denied on this
subnetwork; try an alternate
Service Provider
250
·
·
Timed out waiting for home
MDIS response (see SReg126)
MDLP invalid parameter (251) or
version not supported (252)
Could not access CDPD Network
251, 252
254
255
·
·
Could not deregister NEI because
it was not registered
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DART 200 CDPD Modem User’s Guide
E S-Registers
Table E-2. Register summary (cont.)
Register
S57 (RO)
Value
bitmapped
0,1
Default Description
Network status
0
·
Registration state:
0 = unregistered
1 = registered
2,3
·
Connection state:
0 = no connection
4 = connection
8 = incoming connection
pending
12 = outgoing connection
pending
4
·
·
Auto Registration with
connection (\R2); ATD
command only
0 = Disable Auto-Reg with
connection
16 = Enable Auto-Reg with
connection
Auto Registration with Power
(\R4):
5
0 = Disable Auto-Reg with
Power ON
32 = Enable Auto Reg with
Power ON
6
7
·
·
Auto SLIP Mode
0 = inactive
64 = active
RF in range:
0 = out of range
128 = in range and synchronized
S58 (RO)
bitmapped
0
185 PAD status
·
·
·
·
Auto transmit mode on; see \T
command
Manual transmit mode on; see
\M command
Flow control mode; see \Q
command
Data forwarding character
option; see \F command
Unused
1
2,3
4,5
6
7
·
·
PAD Operating Mode; see \O
command
S59 (RO)
S60 (SM)
0..255
bitmapped
0
0
1
Reserved
Value Function
1
2
4
8
Loopback
1
2
3
4
5
Reserved
Force channel selection
RRM logging enabled
16 RRM disabled
32 Receive frame logging
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E S-Registers
Table E-2. Register summary (cont.)
Register
S60 (SM)
(cont.)
Value
Default Description
64 Transmit frame logging
6
7
128 Use power product override
in SReg36
S61 (SM)
bitmapped
0
143
Value Function
1
2
4
8
Reserved
Reserved
Reserved
Enable SLIP header
compression
1
2
3
4
16 Reserved
32 Reserved
64 Reserved
128 Reserved
5
6
7
S62
1.. 3
0
0
Connection Failure - Process Related
(Read-Only)
1
2
·
·
During the connection process
During the transmission of a
packet
3
·
During the reception of a packet
S63 (RO)
24, 67...82
24
Connection Failure - Probable Cause
·
No socket available
67
·
Address already in use; for UDP
server (in client mode with
backward compatibility specified)
the destination port cannot be the
same as the listening port.
69
70
71
·
·
·
Network is down
Network is unreachable
Network dropped connection on
reset
72
73
75
76
78
79
·
·
·
·
·
·
Software caused connection abort
Connection reset by peer
Socket is already connected
Socket is not connected
Connection timed out
Connection refused; for DART to
DART the Server is not active or
is of the wrong type
81
82
·
·
Host is down
Host is unreachable
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E S-Registers
Table E-2. Register summary (cont.)
Register
S64 (SM)
Value
bitmapped
0
Default Description
22
Value Function
Enable Rcv IP broadcast
1
1
2
Enable TCP/IP header
compression
2
3
4
4
8
Reserved
Reserved
16
Enable SER monitoring in
RRM
5
6
7
32
64
Reserved
Reserved
128 Use V1.0 XID overrides
from SRegs 44-47, 15-16
S65 (SM)
S66 (SM)
0..255
0..255
3
2
Reserved
Limit for undirected chan.search in
intra-area xfer state (# times)
Limit for intra-area xfer channel search
through list (# times)
S67 (SM)
0..255
20
S68 (SM)
S69 (SM)
0..255
bitmapped
0
20
108
Reserved
Value Function
1
2
4
Reserved
Reserved
1
2
Use BLER threshold to
channel hop
3
4
5
8
Reserved
16
32
Reserved
Do not send optional EID
with ESH
6
7
64
Send RR/RNR poll during
channel hops
128 Reserved
S70
S71
0..255
0..100
10
6
Ping wait timeout (sec.)
Ping data length field (in 10 byte
increments)
S72 (SM)
S73 (SM)
S74 (SM)
S75 (SM)
0..255
0..255
0..255
0..255
5
5
6
8
Reserved
Reserved
Reserved
V1.1 RSSI hysteresis value XID
override (dB)
S76 (SM)
S77
0..255
0..255 ASCII
240 Reserved
30
TELNET escape code character
(generated by CTL-^)
TELNET starting terminal type
Value Function
S78
S79
0, 1
bitmapped
0
1
0
1
Enable graceful TCP
shutdown
1-7
--
Reserved
S80 (SM)
0..255
250 Reserved
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DART 200 CDPD Modem User’s Guide
E S-Registers
Table E-2. Register summary (cont.)
Register
S81 (SM)
Value
bitmapped
0
Default Description
0
Value
1
Function
TCP Server specified via
*A1
1
2
UDP Server specified via
*A2
2-3
4
...
Reserved
16
32
...
TCP Server active
UDP Server active
Reserved
5
6-7
S82 (SM)
Bitmapped
0
2
Value Function
1
Enable friends only mode
1
2
Enable UDP backwards
compatibility mode
2
3
4
8
Enable UDP receive locking
Enable UDP client to accept
a reply from any source
Enable UDP client to reply to
source of last message
Reserved
4
16
3-7
...
S83 (SM)
S84 (SM)
S85
0..255
0..255
0..255
30
0
0
UDP receive lock timeout (1/10 sec.)
Reserved
TCP Pad only keep-alive char (null);
TELNET uses NOP char
S86
1..255
1..255
120 TCP PAD/TELNET keep-alive
timeout (min.)
S87 (RO)
0
Reserved for Pad and telent AT
command keep-alive control
Reserved
Reserved
Value Function
S88 (SM)
S89 (SM)
S90 (SM)
20
10
8
bitmapped
0
1
Disable RRM interval time
stamps
1
2
2
4
Reserved
Display Channel ID or Power
Product received time
Reserved
3
8
4
5
6,7
16 Reserved
32 Reserved
64 Reserved
S91 (SM)
0..255
3
Wait time for ISC after ESH (wait =
C{S91} x response timer )
Reserved
Reserved
Reserved
S92 (SM)
S93 (SM)
S94 (SM)
0..255
0..255
0..255
0
0
0
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E S-Registers
Table E-2. Register summary (cont.)
Register Value
Default Description
S95 (SM) bitmapped
11
Value Function
0
1
Select CDPD version 1.1
MDLP/SNDCP
1
2
Select CDPD version 1.1
RRM
2
3
4
8
Reserved
For SLIP replace multicast
NEI with point-to-point NEI
Reserved
4
5
6
16
32
64
Reserved
Use V1.1 XID overrides from
S-Registers 45-47,75,98,99
7
128 Reserved
Reserved
Value Function
S96 (SM) 0..255
S97 (SM) bitmapped
0
2
0
1
2
4
8
Reserved
Reserved
Reserved
1
2
3
Restrict channel access to LCI
in S-Register 20
4
5
16 Reserved
32
Use CDPD 1.1 chnl acq when
in V1.0 mode
6
64
View channel scan results
when in V1.1 mode
7
128 Reserved
S98 (SM) 0..255
90
8
CDPD V1.1 channel re-scan interval
XID override (seconds)
CDPD V1.1 channel re-scan RSSI delta
XID override (dB)
RF channel currently being reported
(may not be acquired)
S99 (SM) 0..255
S100 (RO) 1..1023
S101 (RO) 0,1
CDPD available flag: 0=not available,
1=available
S102 (RO) 0...-255
Mean RSSI in dBm for channel being
reported. Valid only if CDPD is
available (SReg101 = 1)
Current Transmit power level:
0=highest, 7= lowest
S103 (RO) 0..7
S104 (RO) 0..255
S105 (RO) 0..100
S106 (RO) 0..100
S107 (RO) 0..65,535
MDBS power product
Current BLER in %
Current SER in %
CDPD V1.0 – Current LASI; CDPD
V1.1 - Current WASI
S108 (RO) 0..65.535
S109 (RO) 0..255
Current SPNI
Current CSI
S110 (RO) 0..65,535
Current Cell Number
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E S-Registers
Table E-2. Register summary (cont.)
Register Value Default Description
S111 (RO) 0..FF (hex)
Current Area/Cell Color code (0xnn
format)
S112 (RO) 0..100
Current Tx BLER in %
S113 (RO) 0..255
S114 (RO)
Current SIE (Symbols in Error)
CDPD V1.1 - Current SPI
CDPD V1.0 - XID RSSI threshold
(threshold, time)
0
0..255, 1..255
-threshold (first parameter) is dB
above -143 dBW
-time (second parameter) in 1/10 sec
is how long RSSI can be below
threshold before a channel hop must
be taken
S115 (RO)
S116 (RO)
S117 (RO)
0
CDPD V1.1 - not used
CDPD V1.0 - XID BLER threshold
(threshold in %, time)
-threshold is 100/(first parameter) %
-time (second parameter) in 1/10 sec
is how long BLER can be above
threshold before a channel hop must
be taken
CDPD V1.1 - not used
CDPD V1.0 - XID SER threshold
(threshold in %, time)
-threshold is 100/(first parameter) %
-time (second parameter) in 1/10 sec
is how long SER can be above
threshold before a channel hop must
be taken
1..100, 1..255
0
1..100, 1..255
bitmapped
0-3
Function (0xnnnn format)
·
·
·
Reserved
Reserved
4-7
8-11
XID RSSI Rcvd - bit 8 = 1 means
yes (CDPD V1.0 only)
12-15
·
Reserved
S118 (RO)
S119 (RO)
S120 (RO)
0
0
0
0
Reserved
Reserved
0..FFFF
# of RCV discarded acknowledged
class packets (0xnnnn)
# of RCV acknowledged class packets
(0xnnnn)
# of TX discarded acknowledged class
packets (0xnnnn)
# of TX acknowledged class packets
(0xnnnn)
MDIS T200 timer value (in 1/10 sec)
(0xnnnn)
S121 (RO)
S122 (RO)
S123 (RO)
S124 (RO)
0..FFFF
0..FFFF
0..FFFF
0..FFFF
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E S-Registers
Table E-2. Register summary (cont.)
Register
S125 (RO)
Value
0..FFFF
Default Description
MES configuration timer value (sec)
(0xnnnn)
S126 (RO)
0..5
Registration protocol states
0
protocol not active
1
waiting for TEI assignment
2
link connection establishment
pending (waiting for UA)
encryption key exchange
pending (SABME sent,
waiting for IKE)
3
4
5
registration pending (ESH
sent, waiting for ISC)
NEI successfully registered
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E S-Registers
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Appendix
F
DART AT Command Set
AT command set usage
AT commands can be concatenated (end-to-end or with a blank between
commands) for up to a length of 80 characters including blanks. Some
examples are shown below.
?
NOTE:
Entering more than 80
characters at one time
will cause and ERROR
message
·
Normal command concatenation
ATE1V1&D0&S1\F3\N2
AT\S?S57?&V
·
White space concatenation (for readability)
AT E1 V1 &D0 &S1 \F3 \N2
Missing parameters on AT commands default to zero. For example, if
you mistakenly entered AT&E (forgetting to specify a value in the range
of 1-4) it defaults to AT&E0, disabling escape code recognition.
Similar problems can arise if you enter invalid commands since the
DART assumes you’re trying to concatenate commands. For example, if
you mistakenly enter AT\N? (an invalid command) the DART assumes it
was a concatenation of AT\N and ? The result is a display of the last
register referenced (due to the AT?), and to set \Jn to \J1 (due to the
AT\N0; the missing parameter defaults to 0). This could cause serious
problems because a change to the channel restrictions (\Jn) could prevent
the modem from being able to acquire a channel or register.
The obvious recommendation here is to use caution when entering
commands. If you get unexpected results, display the register settings
and modem profile with an AT&V command to ensure that you have not
inadvertently altered the modem profile as was outlined above.
Basic AT commands
The DART commands are both a compatible subset and superset of the
de facto industry standard AT command set. A subset because some of
the wireline commands serve no useful purpose in a wireless
environment; a superset because the wireless environment and built in
TCP/IP stack requires additional options to be specified.
For each command, the default parameter value for the factory setup
profile (restored by AT&F) is identified.
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F DART AT Command Set
Table F-1. Commands beginning with letters
A/
Repeat
Repeats the last AT command.
NOTE:
An AT is not required preceding this command.
A
Answer Online
Causes the DART to stop accepting commands and to wait for an incoming connection request on the
active listening port (see also, *L command) for the amount of time specified in S Reg 7 (default - 20
seconds). If a pending connection request (Ring) is already present, the DART accepts the connection
and enters the online state.
Usually issued in response to the RING message generated by a connection establishment request
(Dial) from a TCP client, or the initial incoming data packet from a UDP client. For TCP the
reception of the initial SYN packet from the client initiates the RING.
Any following commands on the same command line are ignored. If input is detected prior to
entering online mode, the command is aborted.
After the incoming call is answered, either by an ATA or by setting S-Register 0 = 1, the source
address of the caller (IP Address and port number) is available in S-Register 53 and can be viewed by
an ATS53?. It cannot be determined by performing an AT&V and viewing S-Register 53.
NOTE:
The preferred method of responding to an incoming connection request is to have the modem in
permanent auto-answer mode (by setting S-Register 0 = 1).
Format:
ATA
Answer online
Result codes:
CONNECT
Connection is established
NO CARRIER
ERROR
Connection not established due to time-out
Connection already established
D
Dial (connection setup)
Issued by a client device to establish a communication session with a server device. What actually
occurs depends on whether a TCP (also telnet) or a UDP session is being initiated.
For TCP (or telnet) the DART accepts a connection setup request containing a destination address
and optional port, validates it, transmits it to the network, and waits for a response from the server
device.
For a DART server an incoming connection request causes a RING message to be generated. If
auto answer is not specified by setting S-Register 0 = 1, the Ring message is repeated every 10
seconds for a total of 60 seconds. If the call is not answered by the server (either automatically or
with an ATA) within the 60-second time period, a NO ANSWER message is returned to the TCP
client.
For UDP the DART accepts the connection setup request, validates it, and stores the destination and
optional port number for later use and enters online mode. However, at this point the server is
unaware of the UDP Dial. No communication with the UDP server occurs until the client sends a
data block to the modem. The data will be combined with the previously stored destination address
and transmitted to the network for routing to the UDP server.
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F DART AT Command Set
Table F-1. Commands beginning with letters (cont.)
For a DART server the initial incoming datagram causes a RING message to be generated. If the auto
answer is not specified by setting S-Register 0=1, the Ring message is repeated every 10 seconds for
a total of 60 seconds.
D (cont.)
If the call is not answered by the server (either automatically or with an ATA) the client is not
informed. However, for a DART UDP server the connection request (and the attached data packet)
remains pending. If an ATA is subsequently issued, UDP generates both a RING and a CONNECT
message and accepts the pending data packet.
If the client's connection request is accepted (TCP), or validated successfully (UDP) a CONNECT
message is generated, the DART enters online mode and is ready to begin communicating with the
server. Any concatenated commands on the same line are ignored. If input is detected prior to
entering online mode the command is aborted.
The destination address can be explicitly given on the command line or can be a stored address string
retrieved from the modem’s Dial Directory (see the S dial modifier below).
Format:
ATDs
s = dial string, plus optional dial modifiers. The dial modifier can precede (T,
P), replace (S), or follow (;) the dial string.
The dial string consists of a destination address (IP address) followed by an optional port number. It
is preceded, and optionally followed, by a dial modifier (see below). The port number, if present, is
separated from the IP address by a forward slash (/). If not present the port number for both the T
(TCP) and P (UDP) dial modifiers default to 23, the standard telnet port .
NOTE:
A DART modem in server mode only accepts calls directed to its listening port (see the *L
command). The default listening port is 2100, which is incompatible with the default dial port (23).
An example of a valid TCP dial string for port 2100 is ATDT123.456.789.2/2100.
Dial modifiers:
Dial modifiers allow additional information or actions to be specified during the connection
origination process. Dial modifiers include T; P; Sn and semi-colon (;).
T
The T modifier enables a TCP connection to be established. The configuration of
the destination address string, as described above, still applies. The T modifier is
the default setting if no modifier is specified. Refer to Chapter 5, DART
Supported Protocols, TCP, for more information on TCP operation
Format:
ATDTs s = destination address string
The P modifier prepares the DART for UDP communication. The configuration
of the destination address string, as described above, still applies. A CONNECT
response only means that the command was accepted, and that the addressing
information was saved to build UDP packet headers for the data that follows. To
actually communicate the destination must have a UDP server function active,
and the source must pass some application data to the DART for transmission.
P
If a DART defined as a server also acts as a client, the destination port number for
any originated calls must be different from the modems listening port if
backwards compatibility was specified. Refer to Chapter 5, DART Supported
Protocols, UDP, for more information on UDP operation.
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F DART AT Command Set
Table F-1. Commands beginning with letters (cont.)
Format:
D (cont.)
ATDPs s = destination address string plus optional modifiers
Follows the T or the P Dial modifier, or replaces the string in the AT*P (PING)
command. It causes one of the modem’s stored destination addresses to be used
by the command involved. See the AT&Z command.
Sn
Format:
ATDTSn Select stored destination address <n> from the modem’s address list
where n = 0 to 9.
The semi-colon (;) dial modifier follows the dial string and causes the DART to
return to command mode when connection setup is complete, rather than to enter
online mode.
;
Format:
ATDTs1; Return to command mode after connection is established (to
destination address string s1) instead of going online.
Result codes:
CONNECT
Connection is established
NO CARRIER
Connection is broken and extended result codes are selected, or command aborted
and extended result codes not selected (see ATX command).
For TCP, the other side of the connection executed an ATH, or the local modem
attempted a data transmission after the RF link was lost.
For TCP or UDP, DTR was dropped to the local modem and &D2 had been
specified.
BUSY
Connection is refused and extended result codes are selected (otherwise NO
CARRIER). For TCP, an invalid port was specified, the appropriate server is not
active, or the remote device is currently connected to another device.
NO ANSWER
No response is received from the destination within the timeout period specified
by S-Register 7 and extended result codes are selected (otherwise NO
CARRIER). For TCP, auto answer was not enabled, or the destination modem
was not reached because it was not registered, or had lost RF coverage.
NO DIALTONE
The local modem is not registered with the network and extended result codes are
selected (otherwise NO CARRIER)
OK
Semicolon (;) dial modifier was used
Connection refused by the network; an extended reason code is written to
registers S62 and S63.
ERROR
PIN Required; see *E command
NOT ENABLED
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F DART AT Command Set
Table F-1. Commands beginning with letters (cont.)
E
F
H
Command Mode Echo
Controls the echoing of characters when the modem is in command mode.
Format:
ATE0
Disable command mode character echo
ATE1
Enable command mode character echo (default)
Result codes:
OK
Valid argument
Invalid argument
ERROR
Online Mode Echo
Controls the echoing of characters when the modem is in online mode.
Format:
Enable online mode character echo
ATF0
Disable online mode character echo; permit remote echo if provided (default)
ATF1
Result codes:
OK
Valid argument
Invalid argument
ERROR
Hang-up (close connection)
Terminates the current connection. The command can be interrupted by input from the Mobile
Application Subsystem (MAS). This allows the terminate connection process to be upgraded from
H0 to H1 if required.
Format:
Transmit pending information, then terminate connection
No action taken; return result code OK
ATH0
ATH1
ATH2
ATH3
Discard pending data, and terminate connection immediately
Discard pending data, terminate connection immediately, and deregister from
the network
Result codes:
Valid argument
Invalid argument
OK
ERROR
I
Identify
Returns information about the DART.
Format:
ATI0
ATI1
ATI2
ATI3
Show modem equipment ID
Show modem software version number
Identify manufacturer
Identify equipment model number
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F DART AT Command Set
Table F-1. Commands beginning with letters (cont.)
Result codes:
I (cont.)
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Must be in service provider mode
O
Enter Online Mode
Instructs the DART to return to the online state. Any following commands on the same command
line are ignored. This command is used to get to online mode following an ATD; command, or to
return to online mode following an escape.
NOTE:
To return to SLIP mode following an escape from SLIP use AT*S.
Format:
ATO
Go/return to online mode
Result codes:
ERROR
Connection does not exist
CONNECT
Successful return to online mode
Q
Quiet Mode
Controls whether result codes are sent to the Mobile Application Subsystem (MAS). If selected,
result codes can be further modified by the V and X commands.
Format:
ATQ0
ATQ1
NOTE:
Disable quiet mode (result codes are sent to the MAS) (default)
Enable quiet mode (result codes are not sent to the MAS)
There are some low intelligence devices (often found when retrofitting CDPD to a landline or
radio based system) that cannot accept any result codes. Q1 is an appropriate setting for that class
of device.
Result codes:
<nothing>
OK
If ATQ1 selected; OK response is suppressed
If ATQ0 selected
ERROR
Invalid argument
S
Select Register
Selects a register for interrogation or modification in the current active profile. Subsequent reads or
writes to the register are accomplished with the ? or = commands, respectively. The S command is
normally used with an appended ? or = . The register remains selected until the next ATS command.
The complete set of S-Registers is described in Appendix E.
Format:
ATSn
Select register <n>
Result codes:
OK
Valid register selected
Unsupported register
ERROR
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F DART AT Command Set
Table F-1. Commands beginning with letters (cont.)
V
Verbose Result Codes
Selects whether the responses to modem commands use terse or verbose format. Terse responses
consist only of a numeric digit followed by a carriage return (register S3), while verbose responses
consist of a text message preceded and followed by a carriage return/line feed. The responses and
their terse/verbose formats are shown below.
NOTE:
Result codes 5 and above must be explicitly enabled by the ATX command.
Command responses containing data are always framed by carriage return/line feed regardless of
the V option selected.
Format:
ATV0
Use terse result codes
ATV1
Use verbose result codes (default)
Terse/Verbose Response Codes
Terse
Verbose
Terse
Verbose
0
1
2
3
4
OK
CONNECT
RING
NO CARRIER
ERROR
6
7
8
9
NO DIALTONE
BUSY
NO ANSWER
BLOCKED
NOT ENABLED
10
A NO CARRIER result code means that the modem did not have an active CDPD channel at the
time the operation was attempted.
A NO DIALTONE result code means that the modem was not registered at the time he operation
was attempted.
A NO ANSWER result code implies that an improper port number was specified, or that the
server does not have auto answer enabled.
** See the ATD command for more information on the above responses
A BLOCKED result code is the result of a PIN Number or Service Provider Key entered
incorrectly three times or the Unblocking Key entered ten times.
The NOT ENABLED code is the result of trying to use a command that requires a PIN, or that
requires that the modem be in Service Provider mode.
** See PIN Management in Chapter 3, CDPD Security Features, Modem Security management, for
more details.
Result codes:
OK
Valid argument
Invalid argument
ERROR
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F DART AT Command Set
Table F-1. Commands beginning with letters (cont.)
X
Extended Result Codes
Selects whether the DART enables extended result codes. By default all result codes are enabled.
Format:
ATX0
Enable only codes 0...4 Extended results are mapped as appropriate to code 0...4
Enable all extended result codes (default)
ATX1
Result codes:
OK
Valid argument
Invalid argument
ERROR
Z
?
Soft Reset
Performs a soft reset on the DART, aborting any active connection, and resets all modem profile
parameters to their saved values. The network registration status is not affected.
Format:
ATZ
Perform soft reset
Result code:
OK
Command complete
Read Selected Register
Returns the value of the register selected by the S command.
Format:
AT?
Read value of most recently selected register
Read value of register <n>
ATSn?
ATS?
Read value of register 0
Result codes:
A numerical value, decimal or hexadecimal (denoted by a leading 0x), representing the contents of
the specified S-Register.
ERROR
Invalid register number
=
Write Selected Register
Alters the value in the currently selected S-Register. The format of the parameter is numeric or text,
depending on the particular register being modified. Numeric values are specified in decimal. If the
S register contains text then this command must be last on the command line.
Format:
ATSn=x
Set register <n> to <x>
AT=x
Sets selected register (last one referenced explicitly) to <x>
Result codes:
OK
Valid parameter value
ERROR
Invalid value for selected register, or register is read only (RO)
Must be in Service Provider mode to alter this register
NOT ENABLED
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F DART AT Command Set
Table F-2. Commands beginning with ampersand (&)
&C
Set DCD Operation
For serial ports, this command defines the usage of the data carrier detect (DCD) signal at the DART’s
RS-232 interface. This signal can be tested by the MAS application to determine if the specified
condition is true or false. Refer to Chapter 8, Application Programming, Data and control interface,
for more information.
Format:
AT&C0
AT&C1
AT&C3
AT&C4
DCD is always active
DCD follows the state of the Connection Established condition (default)
DCD follows the state of RF in Range
DCD follows the state of Registration
NOTE:
When running in SLIP mode in a Windows/95 environment an &C1 value is required
Result codes:
OK
Valid argument
Invalid argument
ERROR
&D
Set DTR Operation
For serial ports, this command defines the DART’s response to the state of the data terminal ready
(DTR) signal at the RS-232 interface. See Chapter 8, Data forwarding, and Data and control interface.
For both the &D1 and &D2 options any data remaining in the packet buffer is transmitted when the
DTR transition is accepted.
NOTE:
If &D1 or &D2 is specified auto-answer is disabled if DTR is or becomes inactive.
Format:
AT&D0
DTR is ignored (default)
AT&D1
Enter command state upon accepting an active to inactive DTR transition.
When this DTR function completes successfully the MAS receives an OK
response
AT&D2
Enter command state and terminate the connection upon accepting an active to
inactive DTR transition.
This is equivalent to executing an escape followed by an ATH2 command.
When this DTR function completes successfully the MAS receives a NO
CARRIER response
Result codes:
OK
Valid argument
Invalid argument
ERROR
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F DART AT Command Set
Table F-2. Commands beginning with ampersand (&) (cont.)
&E
Escape Code Recognition
Allows the recognition of the escape character sequence to be enabled or disabled.
The Escape code is defined in S-Register 2 (default is a +); the escape guard time is defined in
S-Register 12 (default is 50 units; where each unit is 1/50 sec.).
If S-Register 12 is set to 0 the DART escape sequence approximates the Hayes escape sequence.
The escape function can be disabled (not recommended) only if the escape with the &Dn function is
activated.
NOTE:
Setting S-Register 12 = 0 should be avoided if binary data is being transferred, since there is no
preceding or following guard times as the Hayes method provides and an unwanted escape is
possible.
Format:
AT&E0
Recognition Disabled
AT&E1
Enable escape recognition and pass the escape characters onto the network
(default)
AT&E2
Enable escape recognition and filter the escape characters from the output data
stream when the escape sequence is valid
Result codes:
OK
Valid argument
Invalid argument
ERROR
&F
Restore Factory Defaults
Resets the DART active profile and S-Registers to the factory default settings. It does not reset the
NEI list, SLIP address, MAS address, dial directory, or \J, \N, or *A settings.
This command restores the default settings temporarily. In order to make them permanent, follow the
AT&F command with an AT&W command.
Format:
AT&F
Restore factory defaults
Command complete
Result code:
OK
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F DART AT Command Set
Table F-2. Commands beginning with ampersand (&) (cont.)
&L
Set DART Line Speed and Format
For serial ports, this command allows the Mobile Application Subsystem (MAS) to set the line speed
and format. All subsequent communications between the MAS and the DART is at the new speed and
format if the command completes successfully. These settings do not survive a modem power cycle
unless saved with an &W.
The serial port interface to the MAS is configured to the line speed (300, 1200, 2400, 4800, 9600, or
19200), data bits per character (7 or 8), parity (O, E, N) and number of stop bits (1 or 2) specified. If
any of these are invalid none of the settings are changed.
Regardless of the interface speed selected, the airlink speed is still 19200.
The modems default is 9600, 8N1 with autobaud active.
NOTE:
Executing this command disables the modem’s autobaud feature. This is desirable for most
applications. However, autobaud can be reactivated if desired with the AT&L1 command.
Format:
AT&L<s>,<bps>
Deactivate autobaud feature and set the modem as specified
·
·
·
·
s = desired line speed
b = number of data bits (7 or 8)
p = parity (O for odd, E for even, N for none)
s = number of stop bits (1 or 2)
Examples: AT&L9600,8N1
AT&L19200,7E1
AT&L1
Reactivate autobaud feature
Result codes:
OK
Valid argument
Invalid argument
ERROR
&S
Set DSR Operation
For serial ports, this command defines the operation of the data set ready signal (DSR) at the DART’s
RS-232 interface. This signal can then be tested by the MAS application to determine if the specified
condition is true. Refer to Chapter 8, Application Programming, Data and control interface, for more
information.
Format:
AT&S0
AT&S1
AT&S2
AT&S3
Result codes:
OK
DSR is always active (default)
DSR follows the state of the Connection
DSR follows the state of RF in Range
DSR follows the state of Registration
Valid argument
Invalid argument
ERROR
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F DART AT Command Set
Table F-2. Commands beginning with ampersand (&) (cont.)
&V
View Active Profile and S-Registers
Displays the active configuration of the DART modem. The following information is displayed:
communications port settings, the status of AT commands E, V, Q, F, X, &C, &D, &E, &S, \F, \J,
\M, \N, \O, \Q, \T, *A, *B, *C, *G, *K, *R and *T; S-Registers 0 to 99; and the EID number.
Format:
AT&V
View active profile
Result codes:
Sample output of this command can be seen in Chapter 2, Installation and Setup,
Initial testing.
&V+
View Radio Resource Status
Displays the radio resource status data for the DART’s current environment. The information
displayed is from S-Registers 100 through 126.
The format of the output is slightly different for CDPD V1.0 and V1.1. S-Registers 107 and 114
contain different data, and S-Registers 115 and 116 are not used or displayed in V1.1 mode (see
Appendix E for details).
The data includes current channel, synchronization indicator, color code, transmit and receive signal
strength, transmit and receive block error rates, symbols in error, symbols in error rate, WASI, SPNI,
SPI, CSI, LCI, and the XID threshold and duration values for RSSI, BLER, and SER. A complete
description of these data fields is found in Appendix E.
Format:
AT&V+
Result codes:
Sample output of this command can be seen in Chapter 2, Installation and Setup,
Channel acquisition.
&W
Save Active Profile
Saves the current configuration state and all S-Registers in nonvolatile memory. After reset or
power-up this information is restored.
Use the &W command following any changes to the modem setup or S-Registers to preserve the
altered settings through power cycles or reboots of the modem.
Format:
AT&W
Save active profile
Active profile saved
Result code:
OK
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F DART AT Command Set
Table F-2. Commands beginning with ampersand (&) (cont.)
&Z
Save Addresses (Dial Directory)
Allows the user to save commonly used IP addresses in a nonvolatile memory location <n>, where
<n> can be from 0 to 9. These addresses can be used as dial strings, ping targets, or to define friends
(see Friends Only operation under TCP and UDP). A port number can also be included with the
address. A saved dial string can be invoked with the ATD command modifier Sn, or as a ping target
with an AT*PSn.
Format:
AT&Z=string
AT&Zn=string
AT&Z?
Save string in location 0
Save string in location <n>
Display saved strings
Result codes:
OK
Valid argument
Invalid argument
ERROR
Table F-3. Commands beginning with Backslash (\)
\F
Set Data Forwarding Operation
Determines whether the data forwarding characters specified in S-Registers 51 and 52 are included in
the packet transmitted to the remote data service. For the data forwarding characters to be recognized,
manual transmit mode (\M command) must be enabled.
If only a single data forwarding character is required, set S-Registers 51 and 52 to the same value and
select AT\FO or AT\F3 as appropriate. Refer to Chapter 4, Broadcast and Multicast Operations, Data
forwarding, for more information.
Format:
AT\F0
AT\F1
AT\F2
AT\F3
Data forwarding characters are excluded from the packet (not transmitted)
Data forwarding character specified by S51 is included, but S52 is excluded
Data forwarding character specified by S52 is included, but S51 is excluded
The data forwarding characters in both S51 and S52 are included in packets sent
to the remote data service (default)
Result codes:
OK
Valid argument
Invalid argument
ERROR
\J
Restrict Channel Selection
Enables the modem’s choice of cellular channels to be restricted based on certain CDPD Network
parameters. Each active CDPD channel has an associated SPNI and LSAI (CDPD 1.0), or an SPI,
SPNI, and WASI (CDPD 1.1). The user can require that all, some, or none of these parameters match
similar parameters stored in the DART. Doing so limits the channels and/or the geography available for
modem use. Refer to Channel acquisition restrictions, p. 8-20, for more information.
The SPNI, LSAI, SPI, and WASI are entered and displayed using the AT commands ^H, ^I, and ^L.
\J settings are not reset by ATZ, AT-R, &F or by power cycling the modem.
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F DART AT Command Set
Table F-3. Commands beginning with backslash (\) (cont.)
Format:
\J (cont.)
AT\J0
No restrictions on channel selection (default)
AT\J1
LSAI (CDPD 1.0) or WASI (CDPD 1.1) mode . Use only channels that have the
same LSAI or WASI as the active NEI. Will be forced by \N0.
AT\J2
AT\J3
SPNI mode. Use only channels that have the same SPNI as the modem.
Use only channels that have the same SPNI and LSAI (CDPD 1.0) or WASI
(CDPD 1.1) as the active NEI in the modem.
AT\J4
SPI mode. Use only channels that have the same SPI as the modem (CDPD 1.1
only).
AT\J5
AT\J6
AT\J7
SPI and WASI limitations apply (CDPD 1.1 only).
SPI and SPNI limitations apply (CDPD 1.1 only).
SPI, WASI, and SPNI apply (CDPD 1.1 only).
Result codes:
OK
Valid argument
Invalid argument
ERROR
\M
Manual Transmit Control
Controls the recognition of data forwarding characters by the packet assembler while in online mode.
If enabled, the DART recognizes the reception of either of the two data forwarding characters from the
MAS as a condition to transmit any pending data. The data forwarding characters are defined in S-
Registers 51 (default is 13 <CR>) and 52 (default is 26 <SUB>). Refer to Data forwarding, p. 8-8, for
more information.
The AT\F command determines whether the forwarding characters are themselves included in the
packet. If manual transmit control is disabled, any forwarding characters are included in the packet
regardless of their disposition as defined by the AT\F command.
Format:
AT\M0
Disable recognition of data forwarding character (default)
AT\M1
Enable data forwarding character recognition, and use the conditional status of
the AT\F command
Result codes:
OK
Valid argument
Invalid argument
ERROR
\N
Set Side Preference
Allows the MAS to set the modems side preference. The side preference identifies the CDPD Service
Provider and determines which group of cellular channels the modem searches for a useable CDPD
channel.
\N settings are not reset by ATZ, AT-R, or power cycling the modem
Format:
AT\N0
Home only mode. Alias for (and forces) \J1; does not specify a side setting.
Only allows use of channels that have the same LSAI (CDPD 1.0) or WASI
(CDPD1.1) as the active NEI
AT\N1
A side only
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F DART AT Command Set
Table F-3. Commands beginning with backslash (\) (cont.)
Format:
\N
(cont.)
AT\N2
AT\N3
AT\N4
B side only
A side preferred (default)
B side preferred
Choose \N3 or \N4 only if the modem is used in a visiting (traveling) application
Result codes:
OK
Valid argument
Invalid argument
ERROR
\O
Select PAD or Telnet Operating Mode
Allows the user to select Packet Assembler/Disassembler (PAD) mode, or telnet mode for modem
operations. Refer to PAD operating mode, p. 8-25, for more information.
Telnet mode logs on a user to a remote host by emulating an ASCII terminal. A telnet session uses TCP
protocol but generates additional packets both during session initiation (when terminal emulation
parameters are being negotiated), and during operation (when host echo is usually used).
PAD mode is used to communicate with specific applications or devices using TCP or UDP and usually
have less overhead than telnet. It also supports binary mode data transfers that telnet does not.
NOTE:
Telnet mode is not appropriate for telemetry applications.
To facilitate telnet setup several related profile parameters are forced by the AT\O command as follows:
\O1
Select telnet mode (default)
F1
Use remote echo when in online mode
Disable manual data forwarding
Enable automatic data forwarding
Select PAD mode
\M0
\T1
\O0
F0
Use local echo while in online mode
Enable manual data forwarding
Disable automatic data forwarding
\M1
\T0
Format:
AT\O0
Select PAD mode
AT\O1
Select TELNET mode (default)
Result codes:
OK
Valid argument
Invalid argument
ERROR
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F DART AT Command Set
Table F-3. Commands beginning with backslash (\) (cont.)
\P
Set PIN Requirement; Change PIN
Allows the user to require, not require, or change the modem’s PIN. The PIN is used as a password to
prevent unauthorized access to the CDPD network. Refer to Chapter 3, CDPD Security Features,
Modem security management, and the AT*E command. The current PIN value cannot be displayed.
The default PIN value is 0000.
The use of a PIN can be required with the AT^F command.
Format:
AT\P+<current PIN>
Require PIN
AT\P-<current PIN>
Do not require PIN (this is the default setting)
The new PIN replaces the current PIN
AT\P=<current PIN>,
<new PIN>, <new PIN>
Result codes:
OK
Valid argument
ERROR
BLOCKED
Invalid argument, or function in conflict with ^F command
Command ignored (see AT*U command)
\Q
Set Flow Control Operation
Specifies the flow control method used by the DART. Refer to Chapter 8, Application Programming,
Flow control considerations, for more information
Format:
AT\Q0
No flow control
AT\Q1
Bi-directional XON/XOFF flow control
Hardware flow control (default)
Both
AT\Q2
AT\Q3
Result codes:
OK
Valid argument
Invalid argument
ERROR
\R
Network Registration Control
Causes the modem to register or deregister with the CDPD network. Upon deregistration, any
outstanding connection is terminated and the DART can no longer participate in network operations.
S-Register 13 contains the registration timeout value (default = 60 seconds). An S13 value of zero in
combination with the \R4 option puts the DART into automatic registration mode. Refer to Chapter 8,
Application Programming, Automatic registration, for more information.
Format:
AT\R0
AT\R1
Deregister from the network. Also resets automatic registration mode until the
modem is reset.
Register as an active MES on the network (default)
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F DART AT Command Set
Table F-3. Commands beginning with backslash (\) (cont.)
Format:
\R
(cont.)
AT\R2
Register when connection is established, deregister when connection is
terminated. Can be used only if the modem is operating as a client.
AT\R3
AT\R4
Turn off \R2 option
Auto-register when modem is powered on. If S-Register 13 is set to zero this
option puts the modem into automatic registration mode.
AT\R5
Turn off \R4 option
Result codes:
OK
Command successful
ERROR
Unsuccessful completion; see S-Register 56
PIN Required; see *E command
NOT ENABLED
\S
Set Subscriber Identity
Displays the modem's NEI (IP Address) list (or configuration), and also to select or deselect, the NEI to
be used for network registration. It supports both point-to-point (normal) and multicast (if being used)
IP Addresses. The CDPD Service Provider provides the IP addresses.
NOTE:
The multicast NEI must be selected prior to registering the point to point NEI since they must be
registered as a pair.
Format:
AT\Sn
Select the NEI in slot <n> as the active IP Address, where <n> = 0 - 9.
AT\S+n
Select the NEI in slot <n> as the multicast IP Address. The active NEI slot may
not be selected.
AT\S-n
AT\S?
De-select address <n> as the active or multicast NEI
Display the IP Address list. The active NEI is marked by an <*>, the selected
multicast NEI is marked by a <+>
Result codes:
OK
Valid argument
Invalid argument
ERROR
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F DART AT Command Set
Table F-3. Commands beginning with backslash (\) (cont.)
\T
Automatic Transmit Control
Enables the inter-character time-out data forwarding operation of the packet assembler in online mode.
When the time between characters received from the MAS exceeds the time-out value specified in
S-Register 50, the data in the packet buffer is transmitted. The time-out value is specified in tenths of
seconds; the default is 20 (2 seconds). Refer to Chapter 4, Broadcast and Multicast Operations, Data
forwarding, for more information, and Chapter 8, Application Programming, Binary data transfer, for
more information.
Format:
AT\T0
Disable automatic timed transmission
AT\T1
Enable automatic timed transmission (default)
Result codes:
OK
Valid argument
Invalid argument
ERROR
Table F-4. Commands beginning with asterisk (*)
*A
Select Server Type
Specifies the type of server to be used and can be issued at any time, stopping the current server process
and starting the requested process. Only one server type can be active at a given time.
The current server option can be viewed by inspecting the *An option in the modem profile by use of the
AT&V command.
Format:
AT*A0
No server process. This is the default setting and is appropriate if the attached
device always operates in client mode, for example, always originating connection
requests with an ATDT command.
NOTE:
This command must also be used as an intermediate step when switching server
types.
AT*A1
AT*A2
Selects TCP server process. This allows the modem to accept incoming TCP
connection requests when in command mode and is consistent with earlier versions
of the modem software. Refer to Chapter 5, DART Supported Protocols, Basic
UDP, for more information.
Selects UDP server process. This allows the modem to accept incoming UDP data
packets when in command mode. Refer to Chapter 5, DART Supported Protocols,
UDP Server characteristics for more information.
Result codes:
OK
Requested server mode is set.
Invalid argument.
ERROR
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F DART AT Command Set
Table F-4. Commands beginning with asterisk (*) (cont.)
*B
*C
*E
Enable/Disable Reception of CDPD Broadcasts
Enables or disables the reception of IP broadcast packets. Refer to Chapter 4, Broadcast and Multicast
Operation, for more information.
Format:
AT*B0
Disable CDPD broadcast reception (default)
Enable CDPD broadcast reception
AT*B1
Result codes:
OK
Valid argument
Invalid argument
ERROR
Enable/Disable SLIP Header Compression
Enables or disables SLIP mode header compression (V-J compression) between the MAS and the DART
modem. The setting for this parameter must match the compression setting in the TCP/IP stack in the
MAS for SLIP to be operational.
Format:
AT*C0
Disable SLIP TCP header compression
AT*C1
Enable SLIP TCP header compression (default)
Result codes:
OK
Valid argument
Invalid argument
ERROR
Enable/Disable Network Operations
If PINs are required for network access, this command enables and disables access to the network.
Use of PINs can be required by the AT\P+ or the AT^F1 command. If required, access to the CDPD
network is denied until the proper PIN number is entered with the AT*E+ command. Specifically the
Register (AT\Rn) and the Dial (ATDx) commands are not allowed. Once the PIN is entered, network
access is allowed until the modem is power cycled, or until access is disabled by the AT*E- command.
The modem becomes BLOCKED after three consecutive incorrect PIN entries are made. This condition
can be cleared with the AT*U command.
Format:
AT*E+<pin>
AT*E-
PIN entry; the user is prompted for the PIN when establishing connection to the
network. The default PIN value is 0000.
Disallow network access commands and require PIN reentry in order to reestablish
network connection.
Result codes:
OK
Valid argument
Invalid argument
Command ignored
ERROR
BLOCKED
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F DART AT Command Set
Table F-4. Commands beginning with asterisk (*) (cont.)
*G
SLIP Multicast Address Selection
Permits the user to specify whether the multicast NEI or the modem’s active point-to-point NEI is
passed, as the multicast data packet’s destination address, across the SLIP interface to the user’s
TCP/IP stack in the MAS. This capability is needed to support certain TCP/IP stacks that can only
receive non-broadcast packets sent to a specific IP destination address, such as the point-to-point NEI.
Format:
AT*G0
Pass received multicast packets across the SLIP interface to the TCP/IP stack
unchanged.
AT*G1
Replace the IP destination address in the received multicast packets with the
active point-to-point NEI before passing them across the SLIP interface to the
TCP/IP stack (default).
Result codes:
OK
Valid argument
Invalid argument
ERROR
*K
TCP PAD Keep-Alive
Provides a facility to allow modems supporting TCP applications to time out, or keep-alive a TCP
session with no current activity.
This capability can work in transmit only mode, receive only mode or in both modes. It makes use of a
keep-alive character (S register 85) and a keep-alive time-out value (S register 86) to implement the
function. The timer is restarted whenever any data is sent or received. The default time-out value is 120
minutes.
If the timer expires in transmit or transmit/receive mode pending data or the keep-alive character is
forwarded. For a half open connection, this transmission eventually causes the connection to close
because the other end is not able to provide a TCP acknowledgment for receipt of the keep-alive data
packet.
If the timer expires in receive or transmit/receive mode the modem switches to command mode and an
ATH command is issued to close the connection. While in receive mode incoming keep-alive packets
are discarded only if the incoming keep-alive character matches the value in S-Register 85.
For one way keep-alives (transmit only at one end and receive only at the other) set the transmit time-
out value as less than the receive time-out value to ensure proper operation. For keep-alives in both
directions (transmit/receive) set the time-out values at each end as equal. The keep-alive algorithm has
a small amount of hysteresis built in to cause the transmit time-out to occur ahead of the receive time-
out in order to maintain the link.
If there is not a DART on both ends of a session using the keep-alive function, the application at the
host computer end must handle keep-alive character generation and/or discarding.
This facility is primarily used with remote modems in telemetry applications to allow them to time out
if the host side of the session terminates abnormally (crashes). Without this facility, the DART ends up
with a half-open TCP connection requiring a trip to the remote location to reset the modem with a
power cycle. The setting for this is *K2 with S86 set to a value in the 3 to 5 minute range.
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F DART AT Command Set
Table F-4. Commands beginning with asterisk (*) (cont.)
Format:
*K
(cont.)
AT*K0
No keep-alives (default)
Transmit only
AT*K1
AT*K2
Receive (and discard) only
Transmit/receive
AT*K3
Result codes:
OK
Valid argument
Invalid argument
ERROR
*L
Set Listen Port
Specifies the port number that the servers (TCP or UDP) listen on for connection requests or incoming
data packets. This command can be issued at any time. However, the new port does not become active
until the server is stopped and restarted or the modem is reset. Save the new port number with an
AT&W.
Format:
AT*L<n>
Where <n> is in the range of 1025 through 4999 for compliance with industry
standards. The default value is 2100 for backward compatibility with earlier
versions of the modem software.
AT*L?
Display current port number.
Result codes:
OK
Valid argument
ERROR
n
Invalid argument
Current port number
*M
Set MAS IP Address for SLIP
Sets the IP Address of the MAS (terminal) connected to the DART’s serial port. It is required for the
modem to operate in SLIP mode. It is recommended that the modem’s active NEI be used for this
address. Refer to Chapter 5, DART Supported Protocols, for more information.
The value entered can be verified by using the AT\S? command
NOTE:
A MAS address is required to permit the DART to operate in SLIP mode.
Format:
AT*Ms
s = IP Address of MAS (terminal). The form is n.n.n.n
Result codes:
OK
Valid argument
Invalid argument
ERROR
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F DART AT Command Set
Table F-4. Commands beginning with asterisk (*) (cont.)
*P
Ping Remote Host
Issues ICMP Echo Requests to a Remote Host and waits for a response. The wait time-out between pings
and the packet size s defined by the values in S-Registers 70 and 71. Ping runs continuously until stopped
by pressing the RETURN key or until 20 consecutive time-outs occur, at which time the ping ceases and a
summary of ping statistics is displayed.
The default packet size is 68 bytes. The data portion is 10 times the value in S-Register 71 (6); the header
portion is fixed at 8 bytes. The default time-out between Pings is 10 seconds and is found in S-Register
70. Both of these registers can be altered if desired.
Format:
AT*Pn
AT*PS[n]
AT*P
n = target IP address to ping. The form for this is n.n.n.n, for example,
AT*P155.197.21.101
[n] = dial directory index (see AT&Z command). If [n] is not specified the
address in slot 0 is used.
Use last address pinged. If none, an ERROR response is returned.
*R
Automatic SLIP Mode
Enables the end-user to specify that the DART always enters SLIP mode following power on or modem
reset. It is provided to enable Winsock applications to be able to rely on the modem always being in SLIP
mode, particularly following a power off/on cycle.
The end-user needs to be aware that the modem will not be in command mode following power on if this
feature is active. If it is necessary to send AT commands to the modem at initial application startup, an
escape function must be performed (see &E or &D commands) before the modem can respond to AT
commands.
Bit 6 of S-Register 57 (value of 64) indicates that auto slip mode is active. A modem that has acquired a
CDPD channel (128), has Auto SLIP Mode Startup (64) active, and used the auto registration feature (32)
to get registered (1) shows a value of 225 in S-Register 57.
This command needs to be saved with the &W command to become a permanent setting. After setting
and saving, the command does not become active until the modem is power cycled or reset with the
AT-R command.
Format:
AT*R0
Auto SLIP disabled (default)
Auto SLIP enabled
AT*R1
Result codes:
OK
Command accepted
Invalid command
ERROR
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F DART AT Command Set
Table F-4. Commands beginning with asterisk (*) (cont.)
*S
Initiate SLIP (Serial Line IP Mode) Session
Initiates a SLIP session on the serial port. It is also used to return to SLIP mode following an escape.
SLIP mode can be escaped by using the escape sequence or by causing an active to inactive transition
of the DTR lead with &D1 or &D2 specified.
Format:
AT*S
Enable SLIP mode
Result codes:
OK
Command complete
DETECTED ILLEGAL
NEI
MAS or SLIP address is missing
*T
Telnet Keep- Alive
Provides a facility to allow modems supporting telnet applications to time out, or keep-alive a telnet
session with no current activity.
This facility can work in transmit only mode, receive only mode, or in both modes. It uses the non-
intrusive telnet NOP command packet and a keep-alive time-out (S-Register 86) to implement the
function. The timer is restarted whenever any data is sent or received. The default time-out value is 120
minutes.
If the timer expires in transmit or transmit/receive mode pending data or the telnet NOP command is
forwarded. For a half open connection this transmission eventually causes the connection to be closed
because the other end is not able to acknowledge receipt of the data packet.
If the timer expires in receive or transmit/receive mode the modem switches to command mode and
issues an ATH command to close the connection. While in receive mode incoming keep-alive packets
(the telnet NOP) is automatically discarded by the telnet protocol.
For one way keep-alives (transmit only at one end and receive only at the other) set the transmit time-
out value to be less than the receive time-out value to ensure proper operation. For keep-alives in both
directions (transmit/receive) set the time-out values at each end as equal.
The keep-alive algorithm has a small amount of hysteresis built in to cause the transmit time-out to
occur ahead of the receive time-out in order to maintain the link. If there is not a DART on the remote
end of a session using the keep-alive function then the application at the remote end must handle keep-
alive generation and/or discarding.
Format:
AT*T0
No keep-alives (default)
Transmit only
AT*T1
AT*T2
Receive (and discard) only
Transmit/receive
AT*T3
Result codes:
OK
Valid argument
Invalid argument
ERROR
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F DART AT Command Set
Table F-4. Commands beginning with asterisk (*) (cont.)
*U
Unblock Modem - PIN Access
Can be used to unblock the modem if the PIN is forgotten or is entered incorrectly 3 times. The modem
is unblocked for the express purpose of entering a new PIN. Whenever this command is executed,
follow it immediately by the Set PIN command (AT\P=) to set a new (or restore the old) PIN value
when the current PIN is not subject to validation.
If the Set PIN command is not executed the modem remains in the unblocked state until the next power
cycle, or until a command requiring the PIN is successfully executed.
The default unblocking key is 12345678.
If the unblocking key is entered incorrectly 10 times in succession this command also becomes
BLOCKED. This condition can be cleared by using the AT^C command. Refer to Chapter 3, CDPD
Security Features, Modem security management, for more information.
Format:
AT*U+<key>
Result codes:
OK
Enters the Unblocking Key
Valid argument
Invalid argument
Command ignored
ERROR
BLOCKED
Service provider commands
The Service Provider commands provide the user with the means to
initialize the modem for use on the CDPD network, to alter protected
S-Registers, and to execute diagnostic commands.
Table F-5. Enable/Disable Service Provider mode
^P
Enable/Disable Personalization Mode
This command must be issued before any other Service Provider commands can be executed. It puts
the DART into service provider mode and enables the other service provider commands to be executed
as well as permitting data to be stored in protected S-Registers (see Appendix E). The default <key> is
51348954.
Format:
AT^P-
Disable Personalization Mode
Enable Personalization Mode
AT^P+<key>
Result codes:
OK
Valid argument
ERROR
Invalid argument
BLOCKED
An invalid key was used three or more times.
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F DART AT Command Set
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F DART AT Command Set
Clearing BLOCKED status
When the Service Provider key is BLOCKED and an AT^P+ command
is issued, the modem waits 30 seconds before responding with the
BLOCKED response. This is intended to impose a barrier to any
computer-generated attempt to determine the key value by hackers.
Furthermore, at this point only the Master Key clears the BLOCKED
condition.
To clear the BLOCKED condition the AT^P+ command is used with the
Master Key; the default Master Key value is 34895400. This re-enables
the Service Provider key until the modem is power cycled or reset and
the BLOCKED condition is restored.
To permanently clear the blocked condition an AT^C command must be
issued following the AT^P+<master key>. Refer to Chapter 3, CDPD
Security Features, Modem security management, for more information.
Table F-6. Service provider commands beginning with caret (^)
^A
Set IP Address of DART Modem
Loads an IP Address into one of the 10 slots (numbered 0 - 9) in the DART’s NEI list.
This command also resets the authentication credentials (ASN - sequential and ARN - random)
associated with the selected slot.
Format:
AT^A<s>/<n>
<s> =IP Address of the modem followed by /n where <n> is the position in the
modem’s NEI list where the IP Address is stored. Valid values for n are 0 to 9
with the default being 0.
The form of the IP address is nnn.nnn.nnn.nnn/n, for example,
155.174.21.100/5.
AT^A-n
This form of the AT^A command is used to remove the IP address in slot n of
the NEI list. The ASN and ARN for slot n is reset to 0.
Result codes:
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Modem is not in service provider mode
^C
Clear Blocked Status
Clears the blocked status of the PIN, the PIN Unblocking key, and the Service Provider key. It also sets
their respective entry error counters back to 0.
Format:
AT^C
Clear the blocked status of all keys and reset their error counters
Result codes:
OK
Valid argument
NOT ENABLED
Modem is not in service provider mode
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F DART AT Command Set
Table F-6. Service Provider commands beginning with caret (^) (cont.)
^F
Force PIN Usage
Enables the application developer to specify whether or not modem users require PINs. If the carrier
does not require PINs, they can still be required by the user with the AT\P+ command.
Format:
AT^F0
PIN usage is not required (default).
PIN usage is required.
AT^F1
Result codes:
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Modem is not in service provider mode
^G
Set Multicast Group ID (GMID)
Attaches a GMID to the user-defined multicast NEI. It must reference the slot in the NEI table where
the multicast NEI is located.
The GMID is a carrier assigned value and is used by the MDIS, when the multicast NEI is registered,
to put the NEI into the specified multicast group list. Packets directed to the multicast group are
forwarded to all registered group members regardless of their current location.
Format:
AT^G<g>/<n>
where <g> = 0 to 65535
<n> = 0 to 9; default is 0; (see AT^A)
example: AT^G250/2
AT^G-<n>
This form of the AT^G command is used to remove the GMID in slot n of the
NEI list.
Result codes:
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Modem is not in service provider mode
^H
Set Service Provider Identifier (SPI)
Loads an SPI into one of the 10 slots (numbered 0 - 9) in the DART’s SPI table: it applies in CDPD
1.1 mode only. See the \J command in Chapter 2, Installation and Setup, Initial testing, for more
information.
Format:
AT^H<s>/<n>
where <s> = 0 to 65535
<n> = 0 to 9; default is 0; (see AT^A)
example: AT^H250/0
AT^H-<n>
AT^H?
This form of the AT^H command is used to remove the SPI in slot n of the
modem’s SPI table.
Display current SPI table entries
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F DART AT Command Set
Table F-6. Service Provider commands beginning with caret (^) (cont.)
Result codes:
^H
(cont.)
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Modem is not in service provider mode
^I
Set the Service Provider Network ID (SPNI)
Loads a SPNI into one of the 10 slots (numbered 0 - 9) in the DART’s SPNI table. Refer to the \J
command in Chapter 2, Installation and Setup, Initial testing, for more information.
Format:
AT^I<i>/<n>
where: <i> = 0 to 65535
<n> = 0 to 9; default is 0; (see AT^A)
example: AT^I250/0
AT^I-<n>
This form of the AT^I command is used to remove the SPNI in slot n of the
SPNI table.
AT^I?
Display current SPNI table entries
Result codes:
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Modem is not in service provider mode
^L
Set the Local Service Area ID (LSAI) for CDPD 1.0 mode, or the Wide Area
Service Identifier (WASI) for CDPD 1.1 mode
Loads the LSAI or the WASI into one of the 10 slots (numbered 0 - 9) in the DART’s LSAI/WASI
table. Refer to the \J command in Chapter 2, Installation and Setup, Initial testing, for more
information.
Format:
AT^L<w>/<n>
where:
<w> = 0 to 65535
<n> = 0 to 9; default is 0; (see AT^A)
example AT^L250/0
AT^L-<n>
This form of the AT^L command is used to remove the WASI in slot n of the
LSAI/WASI table.
AT^L?
Display current LSAI/WASI table entries
Result codes:
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Modem is not in service provider mode
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F DART AT Command Set
Table F-6. Service Provider commands beginning with caret (^) (cont.)
^S
Set DART SLIP Address
Sets the SLIP IP Address of the Modem. This internal address is a private address between the modem
and the terminal connected to the serial port and is unknown to the network. This address is often
referred to as being the gateway, router or server address by the TCP/IP stacks that support SLIP
operation.
Since the SLIP address is known only to the terminal and the modem, the convention is to use 1.1.1.2
for this address.
NOTE:
A SLIP address is required to permit the DART to operate in SLIP mode.
Format:
AT^Sn
Where n = the IP address of the modem SLIP port. The format is
nnn.nnn.nnn.nnn.
Result codes:
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Modem is not in service provider mode
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F DART AT Command Set
Table F-7 Service Provider commands beginning with dash (-)
-L
Lock on a Specific Channel
Permits the DART to override normal Radio Resource Management functions and lock itself on a
specific channel.
This is useful at Trade Shows where exhibitors are often requested to operate on a specific channel. It is
also helpful during initial testing when it sometimes is necessary to seek out a specific channel.
The modem continues to operate on the assigned channel until the lock is removed, changed to another
channel, or bit 2 in S-Register 60 is turned off.
Format:
AT-L<n>
Locks the modem on channel <n>
AT-L-
Releases the channel lock
Result codes:
OK
Valid argument
ERROR
Invalid argument
NOT ENABLED
Modem is not in service provider mode
-R
Software Reboot of the DART
Reboots (restarts) the DART. It is equivalent to power cycling the modem. Use this command to
activate changes in the modems operating parameters such as \J, \N, *A, *L, IP Address, and CDPD
operating mode (SReg95).
Format:
AT-R
Reboot (restart) the DART
Result codes:
NOT ENABLED
Modem is not in service provider mode
-V
View Radio Resource Management Data
Displays the current value of pertinent Radio Resource Management Data. Some of this data are the
Carrier operating (XID) parameters to be used by the modem; other data is statistical accumulations of
channel acquisition and channel hopping data that is accumulated between modem resets.
NOTE:
To avoid clearing the accumulated statistical data you must not reset the modem.
Format:
AT-V2
View channel stream, quality, and access parameters
View Adjacent Cell Configuration Information
View channel acquisition statistics
AT-V3
AT-V4
AT-V5
View channel hopping statistics
Result codes:
ERROR
Invalid Argument
NOT ENABLED
Modem is not in service provider mode
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F DART AT Command Set
Table F-7. Service Provider commands beginning with dash (^) (cont.)
-Z
Display Current Authentication Credentials
A diagnostic aid when modem registration fails after it has previously been able to successfully
register. It shows the current values for the ASN (sequential) and ARN (random) authentication
numbers.
Zero values imply that the user has inadvertently reset the modem’s credentials, usually by reloading
the IP Address.
Non-zero values imply that the carrier has for some reason reset the IP Address being used, or that the
modem and MDIS have gotten out of synch due to registration protocol issues under marginal
coverage conditions (quite unlikely). The credentials must be forced to match. In the former case, the
carrier must be asked to rest the IP address. In the latter case, both the user and the carrier must reset
the IP Address
Format:
AT-Z?
Display current authentication credentials
Result codes:
ERROR
Invalid Argument
NOT ENABLED
Modem is not in service provider mode
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Appendix
G
Loading DART 200
Firmware
Periodically, the DART 200 firmware needs to be updated, because of
improvements to the DART’s capabilities, corrections for problems, or to
keep pace with the evolving CDPD standard. When this need occurs, a
ZIP file containing the upgrade materials will be available on the Sierra
Wireless Web site. If you do not have Internet access this file will also be
available on diskette. The ZIP file will contain the new firmware, a
download program, and a README file with instructions for loading the
firmware onto your DART 200 modem.
The download program runs under DOS, and can run as standalone or in
a DOS window under Windows. To reduce the possibility of time-outs it
is recommended that the files and program be copied to a hardfile before
starting execution. Time-outs can still occur if running under Windows.
If a retry or two does not eliminate the timeout problem, try to download
at a lower speed. If that also times out then run the download function as
a standalone program outside of Windows.
When the download is complete the last step in the process is for the
loader to issue an AT&F&W to restore and save the DART’s factory
defaults. If the modem is personalized for application use, reprogram the
modem with its application specific profile and S-Register settings.
However, loading the new firmware does not disturb the modem’s IP
address(s) and associated credentials. When the download is complete,
the modem registers on the CDPD network with no problems.
?
NOTE:
The download function
will reset the modem
profile but not the IP
Address or credentials.
Firmware download procedure
Perform the following steps to download the new software to the DART
200.
1. Make the appropriate connections by:
·
·
Connecting the modem to a 12 VDC power supply
Connecting the modem’s RS-232 interface to a serial port on
your PC
2. Power on the modem.
3. Check that the modem’s server functions are inactive before starting
the download process. Start your ASCII terminal emulator and enter
an AT&V command.
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G Loading DART 200 Firmware
·
·
If you see an *A1 or *A2 in the modem’s active profile enter:
AT*A0&W
If you see an *A0, or do not see an *A at all, then proceed to step
4
4. Insert the download diskette into a floppy disk drive on your PC.
Make that drive the active drive by typing the drive identifying letter
(usually a:) at the DOS prompt followed by a colon ‘:’. For example,
C:\> a:
5. The command to download the new firmware is:
download [-fFilename] [-cCOMx] [-bBaud] [-iInterrupt]
where:
-f specifies the file name the download started with
-c specifies the COM port to use (COM1, COM2, COM3, COM4)
-b specifies the baud (9600, 19200, 38400)
-i specifies the port interrupt number (3, 4, 5, 7)
[ ] indicate optional parameters
?
NOTE:
The COM2 default
might not be correct for
many machines;
however, the remaining
defaults are usually
correct.
The defaults are: file.hdr, COM2, 38400 baud, interrupt 3.
6. To use all the default settings simply enter: download
7. An example using COM1 at 19200 baud is:
download -cCOM1 -b19200
8. If any errors occur during the download they are displayed along
with instructions on what to do about it.
9. The completion status is shown in the download window.
10. Help information can be displayed any time the DOS prompt is
displayed by entering: download -h.
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Appendix
H
Problem Sheet
If you are having trouble with your modem, please call Sierra Wireless
Support (604.231.1100). If it is necessary to return the modem for repair,
you will be given an RMA number and asked to fill out this form and
return it with the modem. Do not return the modem without obtaining an
RMA number.
Sierra Wireless Inc.
#260 13151 Vanier Place
Richmond, British Columbia
V2V 2J2
Tel. 604.231.1100
Fax. 604.231.1109
Date:___________________
RMA No.________________
Company Name
Contact
Address
City
State/Province
Zip/Postal Code
Telephone
Fax
Email
Serial Number
Problem Description
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H Problem Sheet
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Glossary
Acronyms
AMPS
Advanced Mobile Phone System
Original name given to the analog voice cellular
telephone system. The standard for cellular telephone
service in North and South America plus some Pacific
rim countries. CDPD uses the same cells and RF channels
as AMPS.
API
Application Programming Interface
Authentication Random Number
ARN
One of two numbers used as part of the CDPD
authentication procedure. See also, ASN.
ASCII
American Standard Code for Information Interchange
An 8-bit data code used by most PCs and many telemetry
devices.
ASN
Authentication Sequential Number
One of two numbers used as part of the CDPD
authentication procedure. See also, ARN.
AT command
A set of modem commands, preceded by an AT,
originally developed by Hayes, Inc. for their modems.
The structure, but not the specific commands that vary
greatly from manufacturer to manufacturer, is a de facto
modem industry standard.
BLER
bps
Block Error Rate
A measure of the percentage of data blocks that could not
be fully corrected by the FEC scheme.
bits per second
The actual data speed over the transmission medium. It is
not necessarily equivalent to baud. See also, baud.
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Glossary
CDPD
Cellular Digital Packet Data
Wireless radio frequency (RF) packet switched data
communication services. A communications system,
operating over the existing AMPS cellular infrastructure,
that provides services between Fixed End Systems (F-ES)
and Mobile End Systems (M-ES).
CLNP
CMIP
COM
ISO Connectionless Network Protocol
Common Management Information Protocol
Abbreviation for communications
Generally referring to the serial communications port of
a computer.
CTS
Clear To Send
One of the RS-232 signal lines. Used in hardware flow
control
DART
Data Access Radio Transceiver
Short form of MC-DART, the original product name that
stood for Mobile Cellular Data Access Radio Transceiver.
dBm
dBW
DB-9
DB-25
DCD
A logarithmic (base 10) measure of relative power (dB
for decibels); relative to milliwatts (m).
A logarithmic (base 10) measure of relative power (dB
for decibels); relative to one watt.
A standard 9-pin connector of a type commonly found on
communications cables and used by PCs and modems.
A standard 25-pin connector of a type commonly found
on communications cables and used by PCs and modems.
Data Carrier Detect
One of the RS-232 signal lines. Usually used to indicate
the presence of the carrier frequency.
DCE
DNS
DSR
Data Communication Equipment
The official carrier name for the modem. A DCE is
designed to be interconnected with a DTE.
Domain Name Server
Internet server that supplies mapping from domain names
to IP addresses.
Data Set Ready
One of the RS-232 signal lines. Used to signal the
attached device (DTE) that the modem (DCE) is ready to
communicate (powered on).
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Glossary
DTE
Data Terminal Equipment
The official carrier name for the device (PC, MDT, RTU)
attached to the modem (DCE).
DTR
Data Terminal Ready
One of the RS-232 signal lines. Used to signal the modem
(DCE) that the attached device (DTE) is ready to
communicate (powered on). Can also be used by the
modem to escape from data mode to command mode.
EIA
EID
Electronic Industries Association
A standards setting body.
Electronic Identifier
This is a unique, 48 bit number permanently installed in
the modem.This is used by the MDIS to identify the
modem.
ESH
End System Hello
The M-ES initiated final step in the registration process, it
contains the M-ES authentication credentials as well as
additional optional parameters.
ESN
F-ES
FEC
Electronic Serial Number
For CSC only. The ESN serves the same basic purpose in
circuit-switched as the EID does for CDPD.
Fixed End System
This refers to the host computer as a component in the
CDPD network.
Forward Error Correction
Used by MAC layer protocol to correct for airlink data
errors. Implementation uses Reed-Soloman algorithm that
divides the 378-bit airlink block into 63, 6-bit symbols
and can correct a block with errors in up to seven
symbols.
FTP
File Transfer Protocol
A TCP/IP based file transfer protocol.
(Multicast) Group Member Identifier
GMID
A unique ID for a specific multicast group to which
multiple modems can belong. A modem can be a member
of several multicast groups. Used by the MDIS in
combination with the multicast NSAP to facilitate routing
of multicast messages.
GMSK
Gaussian Minimum Shift Keying modulation
The CDPD modulation scheme.
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Glossary
IEEE
Institute of Electrical and Electronics Engineers
A standards setting organization.
MDIS Key Exchange
IKE
IP
The MDIS initiated first step in exchanging encryption
keys with the M-ES.
Internet Protocol
The basic Internet transport mechanism. In CDPD it
operates above the MDLP layer. Also, a layer 3 network
layer protocol.
IP Address
ISC
Your unique address on the Internet. This is the
equivalent of your phone number on the CDPD network.
Each modem must have an IP Address to operate on the
network
Intermediate System Configuration
Set by the MDIS as the final step in the registration
process. It contains the registration status code, and also
the updated random authentication number if the
registration was successful.
ISO
International Standards Organization
A communications standards setting group.
Local Area Network
LAN
In CDPD, the LAN usually attaches the F-ES to a
network router
LCI
Local Cell Identifier
LSAI
Local Service Area ID
CDPD 1.0 term; replaced by WASI in CDPD 1.1.
Medium Access Control
MAC
The CDPD Airlink protocol, that also provides FEC.
Controls the sharing of the Airlink resource among
multiple users. Operates between the physical and MDLP
layers.
MAS
Mobile Application Subsystem
Refers to the combination of the DART and the attached
remote device (PC or user terminal device).
MDIS
Mobile Data Intermediate Station
Computer device that serves as the control point for
CDPD in a specific area. The MDIS accepts information
from the MDBS and processes and sends the information
by routers to the appropriate F-ES.
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Glossary
M-ES
Mobile End System
Refers to the DART as a component in the CDPD
network
MDBS
MDIS
Mobile Data Base Station
Cellular tower serving a specific geographical area.
Communicates by radio with the DART and by landline,
microwave, etc. with the MDIS. See also, cell.
Mobile Data Intermediate Station
Computer device that serves as the control point for
CDPD in a specific area. Accepts information from
MDBS and processes and sends the information by
routers to the appropriate F-ES.
MDLP
MDT
Mobile Data Link Protocol
The link layer protocol used in CDPD. Operates between
the SNDCP and MAC layers. Provides framing, data link
connection, sequence control, and flow control functions.
Mobile Data Terminal
An alternate name for a mobile MAS.
Mobile Network Registration Protocol
Mobile Telephone Switching Office
MNRP
MTSO
Some carriers locate their MDIS at the MTSO
(pronounced mitso).
NEI
Network Entity Identifier
The official name for the IP Address. A 32-bit identifier
normally expressed in dotted decimal (162.147.11.49).
The NEI is a component of the NSAP.
NEMA
NSAP
National Electrical Manufacturer’s Association
A standards setting body.
Network Service Access Point
The definition of the point where the service user and
service provider systems meet. The NEI is accessed
through the NSAP by end-users.
OPR
Abbreviation for the Operate light on the DART
Indicates power on status (slow blink), and relative signal
strength (faster blink to solid on).
PAD
PIN
Packet Assembler - Disassembler
Personal Identification Number
Part of the optional CDPD security system.
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Glossary
PPP
Point-to-point protocol
An alternative communications protocol used between
computers, or between computers and routers on the
Internet. An enhanced SLIP. See also, SLIP.
RC4
The encryption algorithm used by CDPD for data
transmissions between the M-ES and the MDIS.
RF
RI
Radio Frequency
Ring Indicator
One of the RS-232 signal lines. Not currently used by the
DART.
RRM
Radio Resource Management
The process of managing CDPD channel acquisition,
channel hopping, cell transfer, and transmitted signal
strength.
RS-232
An EIA hardware standard; it defines the most common
type of serial communications port hardware. It covers
signal definitions, pin assignments, voltage and
impedance levels, and inter device-signaling rules.
RSSI
RTS
RTU
Receive Signal Strength Indication
The signal power level at the antenna of the modem,
usually measured in dBm. See also, dBm.
Request To Send
One of the RS-232 signal lines. Used in hardware flow
control.
Remote Terminal Unit
Another name for a MAS; usually implies a fixed location
telemetry device
RXD
Received Data
One of the RS-232 data lines.
Set Asynchronous Balanced Mode Extended
SABME
Sent by the M-ES as the first step in CDPD link
establishment.
S-Registers
Status Registers
A set of storage locations within the modem that hold
status and control information for use by the modem
firmware and the users application. Many can be set by
the user when configuring the modem, or when activating
diagnostic functions.
SER
Symbol Error Rate
Percentage of symbols in error. See also, SIE.
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Glossary
SIE
Symbols In Error
Count of how many 6-bit symbols (used by the FEC to
organize the data stream) were in error in the last data
block. See also, FEC.
SIM
Subscriber Identity Module.
The part of the modem containing the IP Address and
authentication credentials
SLIP
Serial Line Internet Protocol
The original alternative communications protocol used
between computers, or between computers and routers on
the Internet. See also, PPP.
In CDPD the modem will operate in SLIP mode when the
TCP stack function is provided by software rather than
the modem.
SPI
Service Provider Identifier
An alternate identifier for a CDPD service provider. Can
be used for special services or billing purposes (CDPD
1.1 only).
SPNI
SNDCP
SNMP
SU
Service Provider Network Identifier
A unique numeric code used to identify the CDPD service
provider.
Subnetwork Dependent Convergence Protocol
Operates between the MDLP and IP layers. Provides
compression, encryption, and segmenting functions.
Simplified Network Management Protocol
Permits remote monitoring and control of communication
devices.
Subscriber Unit
This refers to the DART as a component in the CDPD
network
TCP
Transmission Control Protocol.
A guaranteed packet delivery Internet protocol that is
built on (uses) Internet Protocol (IP) as a base. Often
referred to as TCP/IP
TEI
Temporary Equipment Identifier
A data link layer frame address that identifies a specific
M-ES as the source or destination.
TNC
TXD
An RF connector type commonly used with the coaxial
cables on cellular antennas
Transmitted Data. One of the RS-232 data lines
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Glossary
UA
Unnumbered Acknowledgement
The MDIS response to a SABME from the M-ES when a
CDPD link is being established.
UDP
User Datagram Protocol
A low overhead, nonguaranteed packet delivery IP
protocol A standard TCP/IP protocol that allows an
application on one machine to send a datagram to another
application on another machine.
V.42bis
WASI
A data compression standard. Optionally used in CDPD
to reduce traffic between the modem and the MDIS. Can
improve throughput in high volume applications.
Wide Area Service Identifier
A unique identifier for a business group of licensed
CDPD service providers. Used as a marketing identifier
(CDPD 1.1 only)
XID
A type of MDLP frame used to exchange configurable
communication protocol parameters between an M-ES,
MDBS and/or MD-IS.
X-OFF
Transmission (of data) Off
A short message, sent by the receiver to the sender, to
cause data transmission to the be suspended. When the
receiver is ready to proceed, it sends an X-ON to cause
transmit resumed.
X-ON
Transmission (of data) On
A short message, sent by the receiver to the sender, to
cause a suspended transmission to be resumed.
Terms
asynchronous
A method developed to transmit randomly occurring
characters as they appear. Each character (usually 8 bits)
is preceded by a start bit and followed by at least one stop
bit to maintain bit synchronization between the
transmitting device and the modem.
authentication
The CDPD procedure used to ensure that the user of an
NEI is legitimate. This procedure occurs during modem
registration.
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Glossary
baud
A unit of signaling speed which represents the number of
discrete conditions or signaling events per send that are
transmitted or received over the link.
The frequency at which the transmission medium is
modulated.
Often used incorrectly to state data transmission speed.
By using various modulation schemes it is possible to
encode multiple bits/baud. See also, bps.
block
byte
In CDPD, a 378 bit Reed-Solomon codeword, consisting
of 63 6-bit symbols, 47 of which are data, and 16 of
which provide block parity.
An 8 bit data symbol of which there are 256 possible
combinations. Bytes are normally represented by 2
hexadecimal (0-F) digits. If the symbol can be displayed,
printed, or is used for control purposes it can also be
referred to as a character (ASCII for example). Not all
bytes are characters by this definition.
carrier
cell
The signal you hear from your modem when it is not
transmitting information, but is still in communication
with another modem.
The area surrounding a cellular tower where RF
transmissions can be received at an acceptable signal
strength. For CDPD operations the MDBS is located at
the cell site.
character
Any symbol that is text that can be displayed on the screen,
such as ASCII. Generally represents an 8-bit element of data.
See byte.
color code
A numeric identifier used to distinguish between adjacent
components of CDPD networks (MDBSs, MDISs). Used
to detect interference, or transfers between network
components.
CONNECT
With a Hayes-compatible modem, when this message
shows up on your screen, the modem is telling you it has
dialed the phone number (in Originate mode), got an
answer, received a carrier, and responded. You can now
start communications with the other computer.
data
Information exchanged between a source and
destination. This can consist of a single bit or a long
string of bits, depending on the application.
flow control
A standard for controlling the flow of data, in either
direction, between a modem and an attached device to
prevent overruns. Implementation can be by hardware
(RTS/CTS) or software (XON/XOFF) means. Sometimes
called handshaking.
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full duplex
Communications operation where simultaneous two-way
data transmission occurs across the data link. Devices
using this method can send and receive at the same time.
half duplex
Communications operation where data transmission
occurs in either direction but not at the same time.
Devices using this method can’t receive while sending or
vice versa.
handshaking
parity
Another term for flow control.
A simple method of detecting if the character just
received over the link is what was transmitted. A single
bit is added to the binary string of bits representing the
character to be transmitted. This bit is set to make the
total number of binary ones in the character string plus
the parity bit equal to an even or an odd number. There
are three types of parity: (E)ven, (O)dd, or (N)one.
port
A standard piece of the Internet Protocol address
structure. The port serves as an extension of the IP
Address to permit a single host (one IP Address) to
provide multiple servers (applications) each defined by its
unique port number.
power
product
A carrier configurable MDBS parameter defining the
desired relationship between received and transmitted
signal strength.
Restart
To turn off and then turn on a computer.
roaming
Used to describe the situation where a user from carrier A
is operating in the service area of carrier B.
Status
Registers or
S-Registers
RAM locations inside the modem that hold information
about certain functions that the modem performs. An
example is S9 (the ninth S-Register) that holds the
information on how long to wait for the modem tone
(carrier) to show up before hanging up.
stack
Refers to the TCP protocol stack, so-called because it is
composed of a number of protocol layers (physical, data
link, network, transport, and so on). Required to operate
with Internet Protocol. Can be implemented in software
(PC), or hardware (DART firmware). Trumpet is a
software stack.
start bit
stop bit
The bit preceding each asynchronous character. Signals
the receiving modem that a new character is starting.
There is always 1 start bit.
There is at least 1 stop bit at the end of each character to
be transmitted (sometimes two). One is typical. Resets the
modem chip in preparation for receiving the next
character.
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Glossary
synchronous
A method developed to transmit multiple characters (a
data block) at one time. Each block of multiple 8-bit
characters is preceded and followed by a synchronizing
bit sequence to maintain character synchronization with
the modem.
Telnet
A protocol used for remote terminal connection service,
allowing a user to login to a remote host computer and
operate as if they were directly connected to that host.
Winsock
wireless
The Windows Socket interface. A standard API for use
between a user application and the software TCP/IP
stack. Used if the modem is to run in SLIP mode.
A communications link which does not involve a
hardwired connection. An example of a wireless link is
radio.
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wireline
A communications link which does involve a hardwired
connection. An example of a wireline link is the public
switched telephone network.
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Index
Symbols
A (cont.)
&C, 8-16
&C1, 8-4
&C4, 8-4
&D, 5-10, 5-24
&D0, 8-5
&D1, 8-5, 8-11
&D2, 8-5, 8-11
&Dn, 8-3
ATDT, 5-15, 5-17
ATDTSn, 5-15, 8-24
ATH, 5-9, 5-10, 5-29
ATHn, 5-10, 8-20
ATO, 5-10, 5-30
AT?, 1-5
AT&C0, 5-23
AT&D1, 8-16
&E, 5-24
AT&D2, 8-16
&E0, 8-20
&E1, 8-20
&E2, 8-20
&S, 8-16
AT&L, 8-16, 8-21
AT&L1, 8-23
AT&L &W, 5-23
AT&V, 1-5, 2-6, 2-7, 2-9, 2-13, 2-14, 2-15, 5-3, 5-10,
8-22
&S0, 8-4
&S1, 8-4
&S2, 8-4
&S3, 8-4
AT&V+, 2-13, 2-14
AT&W, 2-7, 2-8, 2-9, 2-14, 2-15, 5-6, 8-7, 8-8,
8-12, 8-23
&W, 5-24
AT&Z, 5-14
&Z, 5-2, 5-15, 8-24
AT&Z?, 8-24
AT&Zn=, 8-24
AT*A1, 5-17, 8-3, 8-11
AT*A2, 5-6, 8-3, 8-11
AT*An, 8-12
AT*Bn, 5-5
AT*E, 8-2
AT*G, 4-4
AT*G0, 4-4
AT*G1, 4-4
A
A side
definition, 1-3, 2-7
accessories
DART 200, 1-2
hardware, 1-2
power, 1-2
RF, 1-2
software, 1-2
airlink, 8-17
AT*Ln, 5-6, 5-18, 8-12
AT*P, 2-21, 5-27
AT*PSn, 8-24
role in CDPD network, 1-4
security, 3-1
AT*R0, 5-24
AT*R1, 5-24
speed, 8-23
AT*S, 5-26, 8-6
antennas
ATI1, 2-6, 2-8
ground planes, 2-3
proximity to other antennas, 7-2
See also cellular antenna
AT\J0, 2-7, 2-14
AT\Jn, 8-22
AT\M, 8-17
ASCII
AT\Mn, 5-28, 8-9
AT\N, 1-5
terminal emulators, 2-3, 8-1, 8-2
terminals, 5-28, 8-1
AT\N?, 1-5
keying data on, 8-19
AT\N0, 1-5
AT commands, 1-4
AT\N1, 2-7
echoing, 8-21
AT,\N2 2-7
for setting up DCD and DSR, 8-16
required for setting up TCP, 5-19
required for setting up UDP, 5-11
ATA, 5-6, 5-9, 5-16, 5-18, 8-3, 8-12
ATD, 5-2, 5-15, 8-3, 8-5
AT\Nn, 2-7
ATQ1, 8-12
AT\R, 2-15
AT-R, 2-8, 2-21, 5-24, 8-8
AT\R0, 8-8
ATDn, 8-2
AT\R1, 2-15, 2-19, 8-7
ATDP, 5-2, 5-3, 5-6, 5-7, 5-8, 5-9
ATDPSn, 5-2, 5-8, 8-24
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Index
A (cont.)
C
AT\R2, 8-8
CDPD
AT\R3, 8-8
AT\R4, 2-13, 2-15, 8-7, 8-8
AT\R5, 8-7
acquiring a channel on, 2-4
advantages, 1-3
airlink, 8-23
AT\Rn, 8-6
AT\S, 5-26
AT\S?, 2-6, 2-7, 2-8, 4-3, 5-26
ATS0=1, 5-6, 5-18, 8-12
AT\S+n, 4-3
application structure, 8-2
block transfers, 8-23
broadcast messages, 4-2
broadcast mode, 4-1
channels
AT\S-n, 4-3
BLER of, 2-12
ATSn?, 8-6
ATS13 = 0, 8-8
searching for, 2-10
strongest, 2-11
ATS102?, 2-13
ATS126?, 2-16
ATS13=0, 2-15
ATS53?, 5-3, 5-7, 5-10, 5-15, 5-16
ATS56?, 2-16
class addresses, 5-24
forced hopping, 2-10
initiating communication with, 1-4
Internet addresses, 5-24
modems
ATS57?, 2-12, 2-13, 2-15, 7-2, 8-15
ATS60=1, 2-15
Attention commands. See AT commands
AT\T, 8-17
checking, 4-3
network,1-1, 5-22
authentication services, 3-1, 3-2
carriers, 1-3
AT\Tn, 8-9
auto answer, 5-2, 5-11, 5-14, 5-19, 8-1, 8-12
difference between synchronous, 8-3
enabling the DART on, 5-17
forwarding data to, 8-8
functions, 1-3
IP Addresses, 1-3
operating the DART 200 on, 5-4
overview, 1-3
setting, 5-6, 8-12
Auto SLIP, 1-2, 5-24, 7-2
autobaud, 8-3, 8-18
function, 8-22
reactivating, 8-23
authentication
parity, 8-17
services, 3-1
pinging, 5-27
registering DART on, 5-15, 8-6
role of DART in, 1-4
types, 2-10
protocol layers, 5-26
protocols
B
B side
definition, 1-3, 2-7
backward compatibility, 5-6, 5-9, 5-18, 8-12
function, 5-6
TCP, 5-15
UDP, 5-5
with basic UDP, 5-6
bandpass filter, 7-3
Basic UDP. See UDP
batteries, 7-1
registration, 2-16
security, 3-1
selecting versions, 2-8
session
BLER, 2-11, 2-12, 2-15
checking, 2-11
shutting down, 8-19
signal, 2-10
block error rate. See BLER
broadcast
status sensing, 8-15
supported versions, 1-1
telnet session, 5-28
vulnerability, 3-1
CDPD 1.0, 2-8, 2-12
CDPD 1.1, 2-8
datagrams, 4-2
messages, 5-5
NEI, 4-2
broadcast mode
definition, 4-1
when to use, 4-2
main objective of, 2-11
requirements, 2-12
signal strength, 2-15
switching to, 2-8
CDPD Forum, 1-4
cell dragging
avoiding, 2-12
definition, 2-11
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DART 200 CDPD Modem User’s Guide
Index
C (cont.)
D (cont.)
cellular antennas, 1-2
preferred, 2-5
requirements for DART 200, 2-3
cellular carriers
DART 200 (cont.)
changing profile parameters, 5-30
channel searching, 2-10
client mode, 8-18
contacting, 1-3
client-server capability, 5-14
COM port settings
default, 8-22
command mode, 8-13, 8-16
customizing, 2-6
Wireless Data Forurm, 1-4
Cellular Digital Packet Data. See CDPD
central client application
setting up, 5-19
channel hopping, 2-10
channels
data forwarding feature, 8-8
deregistering, 8-8
cellular, 2-11
description, 1-1
changing in mobile environment, 2-12
forcing, 2-10
dial directory, 8-24
dial list, 5-2, 5-15
hops, 2-10
echo options, 8-21
MDBS, 2-10
EID, 1-3
operating on best, 2-12
RF limitations, 8-22
sorting, 2-11
enabling changes, 8-8
encrypting, 1-4
error handling, 8-1
Clear to Send. See CTS
client mode, 5-6, 5-8, 5-10, 5-17, 8-18
client-server models, 5-6
compressed SLIP. See CSLIP
command mode, 8-5, 8-16
during a reset, 7-1
escape sequence, 8-20
feature limitations, 8-16
firmware capabilities, 1-1
flow control, 8-13
hardware, 8-14
in multicast mode, 4-3, 4-4
initiating UDP communication with, 5-2
installing
definition, 8-3
echo, 8-21
modem lockup in, 8-13
reading S-Registers in, 8-6
returning to, 8-3, 8-20
using autobaud in, 8-22
credentials
in a wet environment, 2-1
in a vehicle, 7-1
Interrupt Service buffer, 8-13
issuing a UDP dial with, 5-2
locating the antenna for, 7-2
leads, 8-15
authentication of, 3-1
CSLIP, 5-23
locating, 2-2
CTS, 8-12
locating the antenna for, 7-2
maximum packet size, 8-10
maximum power output, 2-4
messages, 8-25
lead, 8-14
D
migrating from, 1-2
DART
minimum distance from personnel, 2-1
minimum distance to another antenna, 2-3
online mode, 8-3
built-in protocols, 8-1
firmware, 2-8
UDP server, 5-5, 5-6
DART 100
as compared to 200 and 300, 1-1
basic UDP feature, 5-2
DART 200
operating with CDPD 1.1, 2-11
outages when installed in a vehicle, 7-1
ping values, 5-27
default, 5-27
power cord, 1-2
accessories, 1-2
power requirements, 2-1
putting in online mode, 5-2
registering, 2-15, 3-1, 8-6
automatically at power up, 8-2
response codes, 8-25
role in CDPD network, 1-4
RS-232 DB9 interface, 6-1
RS-232 interface, 8-17
receiving application data from client, 5-9
receiving data blocks from MAS with, 5-3
receiving data from the MAS, 5-15
receiving datagram from another M-ES, 5-4
acquiring channels with, 2-10
antenna requirements, 2-3
applications, 2-1
as compared to 300, 1-2
as compared to DART 100, 1-1
auto registration at power-on, 8-7
autobaud, 8-22
automatic SLIP restart, 5-24
basic UDP feature, 5-2
before you start installing, 2-5
buffer space, 5-10
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DART 200 CDPD Modem User’s Guide
Index
D (cont.)
D (cont.)
DART 200 (cont.)
DTR
dropping, 5-10, 5-26, 8-3
registering, 5-15, 3-1
selecting ports to listen to with, 5-17
sending data to the MAS, 5-3
security, 3-2
lead, 8-16
controlling, 8-20
line, 8-16
server
dropping, 8-20
setting up, 8-12
server mode, 8-18
setting up, 2-5, 2-6, 5-4, 8-2
auto answer, 8-11
E
echo
characters, 8-21
for CDPD network, 5-17
for TCP application, 5-19
for UDP application, 5-11
S-Registers, 2-9
SLIP capability, 5-22
SLIP IP Address, 5-25
standard message from, 8-25
telnet keep-alive feature, 5-29
telnet support, 5-28
for AT commands, 8-21
for online mode, 8-21
in online mode, 5-28, 8-20
locally, 5-29
options, 8-21
request, 5-27
selecting options, 8-21
EID, 1-3
encrypting data
testing, 2-21, 5-27
with airlink, 1-4
encryption, 4-1
services, 3-1
Equipment Identifier. See EID
error codes
troubleshooting, 2-4, 2-16, 8-13
UDP protocol support, 5-1
UDP server capability, 5-4
using AT commands with, 8-3
verifying set up, 2-8
Data Access Radio Transceiver. See DART
data carrier detect. See DCD
Data Communications Equipment. See DCE
data forwarding
obtaining, 8-4
escape characters, 8-20
for telnet, 5-30, 5-31
for DART 200, 8-20
characters, 8-9, 8-11
considerations, 8-17
definition, 8-8
F
F-ES, 4-1, 4-2, 5-11, 5-15, 5-19, 8-17, 8-18, 8-21
role in CDPD network, 1-4
FIFO
operation, 5-29
data packets
for TCP and UDP, 8-11
encrypting, 1-4
queue, 5-7, 5-10
File Transfer Protocol. See FTP
filtering, 2-3, 7-3
firmware
fragmentation of, 8-10
maximum size, 8-23
optimal size, 8-10
supported by DART 200, 2-8
First-In-First-Out. See FIFO
Fixed End System. See F-ES
flow control, 8-14, 8-16, 8-17
considerations, 8-17
for hardware, 8-12, 8-13
for software, 8-12
data set ready. See DSR
Data Terminal Equipment. See DTE
Data Terminating Equipment. See DTE
data terminal ready. See DTR
DCD
setting up lead, 8-16
signals, 8-4
problems for the new user, 8-13
purpose, 8-12
DCE, 6-1, 6-2
interface, 6-1, 6-2, 6-3
modem, 6-2
dial command. See ATD
dial directory, 5-7, 5-14, 8-24
dedicated network, 2-10
DSR
in online mode, 8-13
troubleshooting, 2-4, 8-12
forced hopping, 2-10
friends list, 5-7, 5-15
friends only mode, 1-2, 5-14, 8-24
description, 5-14
lead, 8-16
purpose, 5-7
signals, 8-4
FTP, 5-22
DTE, 5-8, 6-1, 6-2
testing, 5-25
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Index-4
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DART 200 CDPD Modem User’s Guide
Index
G
M
GMID, 2-6, 2-8, 4-3
defining, 4-3
MAS, 4-1, 5-1, 5-3, 5-6, 5-7, 5-9, 5-10, 5-14, 5-15, 5-16,
5-17, 5-26, 8-4, 8-5, 8-6, 8-8, 8-9, 8-11, 8-14,
8-16, 8-18, 8-25
field, 4-3
ground plane, 2-3
Group Multicast Identifier field. See GMID
application operating mode, 5-6
as a server, 5-3, 5-10
AT command support, 8-1
buffer size, 8-13
H
bypass, 8-17
host echo, 5-28
Hardware Flow Control, 8-13,8-14, 8-17
Hayes-compatible. See AT commands
CDPD status sensing, 8-15
data forwarding characters, 8-9
definition, 2-11
determining if server or client, 7-2
devices, 8-13
buffers, 8-13
I
ICMP PING, 4-1
Internet, 5-22
escape sequences, 8-20
function, 8-3
in active mode, 5-8
address classes, 5-24
browsers, 5-22
connection, 5-12, 5-21
IP Addresses
in online mode, 5-8, 7-2
IP Adresses, 5-25
viewing, 5-26
assigning, 1-3
parity, 8-17
DART 200’s list, 4-3
determining if preloaded, 2-6
entering in list, 8-24
entering in the dial directory, 5-14
for DART 200s, 2-6, 5-26
for the DART SLIP Interface, 5-23
for friends only mode, 5-5
for multicast mode, 4-3, 4-4
for SLIP, 5-24, 5-25
for the server, 5-27
friendly, 8-24
responsibilities, 5-16
setting up result codes for, 8-20
timing out, 8-18
MC-DART, 5-2
MDBSs
channel list, 2-10, 4-2
power output control by, 2-4
role in acquiring a channel, 2-10
role in CDPD network, 1-3
sniff -and-hop capability, 2-10
MDIS, 1-4, 3-1, 4-1, 5-12, 5-21
accepting credentials,3-1
authentication, 3-1
in broadcast mode, 4-1
obtaining, 2-21
pinging, 5-27
table, 3-1
referencing in the dial list, 5-15
testing, 2-22
broadcast mode, 4-2
credentials, 3-1
troubleshooting, 8-25
viewing list, 5-26
multicast mode, 4-1, 4-2
role in CDPD network, 1-3
testing, 2-21, 5-27
M-ES, 2-11, 5-4, 5-7
authentication, 3-1
K
keep-alives
broadcast mode, 4-2
cell dragging, 2-12
timer expiry for, 8-19
echoing, 8-21
encryption, 3-1
L
in a multicast group, 4-2
initiating CDPD communication with, 1-4
list of, 4-2
local echo, 5-29
local service area ID. See LSAI
LSAI, 8-22
multicast mode, 4-1
online mode, 5-8, 5-9
PAD, 5-16
storing values for, 8-22
role in CDPD network, 1-3
server mode, 5-7, 5-9, 5-10, 5-13, 5-17
PN1197-00 Revision 1.0
Index-5
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DART 200 CDPD Modem User’s Guide
Index
M (cont.)
O
messages
online mode, 2-19, 5-2, 5-3, 5-8, 5-28, 5-29, 7-1, 8-4
checking character formats in, 8-18
data forwarding when in, 8-9
echo, 5-28, 8-21
broadcast, 4-1, 4-4
receiving, 4-2
DART 200, 8-25
encrypting, 4-1
echo default, 8-21
error, 8-25
listening for incoming, 5-6, 5-18
multicast, 4-1, 4-2
establishing for DART 200, 5-15
for DART 200, 5-9, 5-10
for M-ES, 5-9
starting with AT, 7-2
for the MAS, 5-3
Mobile Application Subsystem. See MAS
Mobile Data Base Stations. See MDBSs
Mobile Data Intermediate System. See MDIS
Mobile End Station. See M-ES
modem echo, 5-28
inter-character time-out data forwarding when in, 8-9
putting DART 200 in, 5-2
troubleshooting, 8-4
P
modes of operation
Packet Assembler - Disassembler. See PAD
PAD
data stream, 4-1
keep-alives, 8-18
PAD operating mode, 5-18, 8-14
client mode, 5-6, 5-8, 5-10, 5-11, 5-17, 8-18
command mode, 5-10, 5-17, 5-24, 7-1, 7-2 8-3, 8-4,
8-5, 8-6, 8-11, 8-13, 8-15, 8-16, 8-18, 8-21, 8-22
online mode, 5-2, 5-3, 5-8, 5-9, 5-10, 5-15, 7-2, 8-3,
8-4, 8-6, 8-9, 8-18, 8-21
parameters
PAD, 5-18
blocksize, 8-23
key, 5-5
server mode, 5-7, 5-9, 5-10, 5-14, 5-15, 5-19, 8-18
Molex connector, 2-1
setting up for PAD operating mode, 5-18
setting up for UDP server, 5-6
using with AT commands, 1-5
XID, 2-11, 2-12
multicast mode
definition, 4-1
set up, 4-2
parity
N
considerations, 8-17
disabling, 5-23
NEI, 2-8, 3-1
active, 5-26
settings, 5-22
broadcast, 4-2
multicast, 4-2, 4-3
defining, 4-3
Personal Identification Number. See PIN
PIN
command, 8-2
entering, 4-3
verifying, 4-3
management system, 3-2
purpose, 3-2
multiple, 5-26
network address, 5-25
point-to-point, 4-4
registered, 5-26
registering, 4-3
troubleshooting, 8-25
NEMA enclosure, 2-1
null modem
requirement, 3-2
ping, 1-3, 5-22
an IP Address, 5-26
command, 2-21
device, 2-21
format, 5-27
network server, 2-21
packet size, 2-21
adapter, 6-2
server, 5-27
cables, 6-3
connector, 6-2
location, 6-2
targetting port numbers, 8-25
testing, 2-6, 2-21
times, 5-27
requirement, 6-1, 6-3
troubleshooting, 2-21, 8-13
to validate SLIP session, 5-27
troubleshooting, 2-19
for DART 200, 5-25
values
for DART 200, 5-27
polling, 5-12, 5-19, 5-21
by host UDP, 5-11
power cord, 1-2, 2-1
Sierra Wireless, Inc.
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DART 200 CDPD Modem User’s Guide
Index
Q
S (cont.)
quiet mode, 8-12
definition, 8-20
signals (cont.)
determining if strong, 2-10
determining strength of, 2-15
determining strength of RF, 2-3
DSR, 8-4
R
radio interference
troubleshooting, 2-15
Receive Signal Strength Indication. See RSSI
receive locking
DTR, 8-5
for the DART 200, 2-3
maximizing reception of RF, 2-3
minimizing blocking of, 2-3
red OPR light indicator, 2-5
RTS, 8-13
definition, 5-6
remote telemetry application
setting up, 5-19
status, 8-4
Remote Terminal Units. See RTUs
Request to Send. See RTS
response codes, 8-25
formats, 8-25
staying on, 2-11
strength for RF, 8-6
strongest, 2-11
testing for loss of, 8-4
result codes
SLIP
extended, 8-21, 8-25
return codes
address for DART 200, 5-25
automatic restart, 7-2
capability, 5-22
enabling, 8-21
for troubleshooting, 2-16
RF signals
blocking, 2-3
RS-232, 6-1
compressing headers, 5-23
description, 5-22
error handling, 8-1
interface, 4-4, 5-25
IP Address, 5-25, 5-26
messages, 4-1
mode, 1-2, 4-2, 4-4, 5-22
automatic, 5-24
escaping, 5-26, 8-20
parameters, 5-23
cable, 2-4
requirements, 6-1
gender changer, 6-3
interface, 7-2, 8-4, 8-12
leads, 7-2, 8-15, 8-18, 8-20
popularization of, 6-1
port, 5-9, 5-15
on DART 200, 1-2
serial port, 8-3
ping, 5-27
specification, 6-1
RSSI, 2-3, 2-11, 2-12
viewing, 2-13
requirements, 8-16
setup for, 5-22
stacks used with, 5-25
starting, 5-26
RTS, 8-12
lead, 8-14
testing, 5-27
RTUs, 5-5
SLIP Header Compression, 5-23
sniff-and-hop, 8-24
channels in, 2-12
S
MDBS capability, 2-10
network, 2-10
security
airlink, 1-4
for DART 200s, 3-2
Software Flow Control, 8-17
SPI, 8-22
friends only mode, 5-7
managment feature, 3-2
Serial Line Internet Protocol. See SLIP
server mode, 5-7, 5-9, 5-10, 5-11, 5-14, 5-15, 5-19, 8-18
service provider ID. See SPI
service provider network ID. See SPNI
Service Provider Key. See SPK
signals
multiple entries for, 8-20
storing values for, 8-20
spiral search, 2-11
SPK
mandatory use of, 3-2
purpose, 3-2
SPNI, 8-22
multiple entries for, 8-22
storing values for, 8-22
attenuation, 7-3
blocking of RF, 2-3
CDPD, 2-10
change in strength, 2-12
DCD, 8-4
PN1197-00 Revision 1.0
Index-7
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DART 200 CDPD Modem User’s Guide
Index
S (cont.)
T (cont.)
S-Registers, 2-5, 2-8, 2-9, 2-12, 2-13, 2-14, 2-15, 2-16,
2-17, 2-18, 2-20
telent (cont.)
echoing, 5-28
escaping, 5-30
13, 8-8
keep-alives, 5-29
50, 2-3, 2-8, 2-9, 2-12, 2-13, 2-15, 2-16, 2-17, 2-19,
2-20, 2-22, 5-3, 5-4, 5-6, 5-7, 5-8, 5-10, 5-14, 5-15,
limitations in binary mode, 8-16
mode, 8-8, 8-12
5-18, 5-19, 5-24, 5-29, 5-30, 8-2, 8-5, 8-6, 8-7, 8-9,
NOP, 5-29
8-11, 8-12, 8-17, 8-19, 8-20, 8-22
port, 5-8, 5-15
51, 5-29, 8-9, 8-11
protocols, 1-2
52, 5-29, 8-9, 8-10
purpose, 8-1
56, 2-17, 8-4
57, 8-4, 8-8
62, 8-4
63, 8-4
remote login, 5-31
removal of binary mode, 5-31
returning to, 5-30
setting up, 5-28
70, 2-21
using, 5-31
71, 2-21
101, 8-4
terminal emulation, 2-6, 5-24
mode, 2-5
102, 8-4
terminal emulators, 2-3, 8-1, 8-2
terse mode, 8-3, 8-12
Transmission Control Protocol. See TCP
Trumpet, 5-26
126, , 2-17, 5-50, 5-3, 5-4, 5-6, 5-7, 5-10, 4-15, 5-8, 5-
15, 5-16, 5-17, 5-18, 5-22, 5-23, 5-27, 5-28, 5-29,
5-30, 8-4
displaying, 2-6
TSR
reading in command mode, 8-6
definition, 2-21
representing, 2-9
reviewing, 2-6
status information
U
UDP, 1-2, 4-1, 4-2, 8-21
application programs, 5-1
basic
analyzing, 8-4
Status Registers. See S-Registers
characteristics, 5-2
T
communication, 5-2
enabling/disabling, 5-4
setting up, 5-4
clients, 5-10
datagrams, 5-9, 5-10
definition, 5-1
dial command, 5-2, 5-3
headers, 5-3, 5-9, 5-10
host setup, 5-11, 5-12
modes, 8-12
multiple applications, 5-22
programming effort, 5-2
receiving multicast messages, 5-5
recovery, 7-2
TCP, 1-2, 8-8, 8-10
activating server, 8-11
capabilities of the DART 200, 5-14
CONNECT message, 8-12
connected state, 7-2
definition, 5-14
friends only, 1-2
headers, 5-15, 8-10
keep-alives, 5-19, 8-18
mode, 8-1
multiple applications, 5-21
port specification, 8-11
recovery, 7-2
server, 5-19
reliability, 5-1
activating, 5-17
remote setup, 5-11
server mode, 5-16
setting up, 5-17
for remote modem, 5-19
host modem, 5-21
samples, 5-19
server, 4-2, 5-2, 5-4, 5-5, 5-10, 8-18
backward compatibility, 5-7
receive locking, 5-7
setting up, 5-6, 5-11
User Datagram Protocol. See UDP
starting a session, 5-14
usage considerations, 8-11
TCP/IP, 5-22
V
vehicle
stacks, 5-22
installing a DART 200 in, 7-1
verbose mode, 8-3, 8-11, 8-21
telnet capability, 5-28
telnet, 4-1, 5-22, 8-10
binary mode considerations, 5-31
description, 5-28
Sierra Wireless, Inc.
Index-8
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DART 200 CDPD Modem User’s Guide
Index
W, X, Y, Z
WASI, 8-22
multiple entries for, 8-22
storing values for, 8-22
wide area service ID. See WASI
Winsock, 5-26
Wireless Data Forum, 1-4
XID parameters, 2-11, 2-12
XID threshold, 2-12
XON/XOFF, 8-12
characters, 5-23, 5-31, 5-29, 8-13, 8-17
PN1197-00 Revision 1.0
Index-9
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DART 200 CDPD Modem User’s Guide
Index
Sierra Wireless, Inc.
Index-10
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NOTES
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PN1197-00 Revision 1.0
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DART 200 CDPD Modem User’s Guide
Notes
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Sierra Wireless, Inc.
Notes-2
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DART 200 CDPD Modem User’s Guide
Notes
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PN1197-00 Revision 1.0
Notes-3
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DART 200 CDPD Modem User’s Guide
Notes
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Sierra Wireless, Inc.
Notes-4
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