Sierra Wireless MP 700 Series Installation manual

MP 700 Series GPS
Rugged Wireless Modem
AT Command Reference
2130309
Rev 3.2

Important Notice
Safety and Hazards
Limitation of
Liability
Preface
Because of the nature of wireless communications, trans-
mission and reception of data can never be guaranteed. Data
may be delayed, corrupted (i.e., have errors) or be totally lost.
Although significant delays or losses of data are rare when
wireless devices such as the Sierra Wireless modem are used in
a normal manner with a well-constructed network, the Sierra
Wireless modem 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, accepts no responsibility for damages of any kind
resulting from delays or errors in data transmitted or received
using the Sierra Wireless modem, or for failure of the Sierra
Wireless modem to transmit or receive such data.
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 POWERED OFF. The Sierra Wireless modem can
transmit signals that 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 POWERED OFF. When
operating, the Sierra Wireless modem can transmit signals that
could interfere with various onboard systems.
Note: Some airlines may permit the use of cellular phones while the
aircraft is on the ground and the door is open. Sierra Wireless
modems may be used at this time.
The driver or operator of any vehicle should not operate a
computer or any other device connected to 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 commu-
nications devices while in control of a vehicle is an offence.
The information in this manual is subject to change without
notice and does not represent a commitment on the part of
Sierra Wireless. SIERRA WIRELESS AND ITS AFFILIATES
SPECIFICALLY DISCLAIM LIABILITY FOR ANY AND ALL
DIRECT, INDIRECT, SPECIAL, GENERAL, INCIDENTAL,
CONSEQUENTIAL, PUNITIVE OR EXEMPLARY DAMAGES
INCLUDING, BUT NOT LIMITED TO, LOSS OF PROFITS OR
Rev 3.2 Oct.05 1

MP 700 Series GPS AT Command Reference
Patents
Copyright
Trademarks
REVENUE OR ANTICIPATED PROFITS OR REVENUE
ARISING OUT OF THE USE OR INABILITY TO USE ANY
SIERRA WIRELESS PRODUCT, EVEN IF SIERRA WIRELESS
AND/OR ITS AFFILIATES HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES OR THEY ARE
FORESEEABLE OR FOR CLAIMS BY ANY THIRD PARTY.
Notwithstanding the foregoing, in no event shall Sierra
Wireless and/or its affiliates aggregate liability arising under
or in connection with the Sierra Wireless product, regardless of
the number of events, occurrences, or claims giving rise to
liability, be in excess of the price paid by the purchaser for the
Sierra Wireless product.
Portions of this product may be covered by some or all of the
following US patents:
5,515,013 5,629,960 5,845,216 5,847,553 5,878,234
5,890,057 5,929,815 6,169,884 6,191,741 6,199,168
6,339,405 6,359,591 6,400,336 6,643,501 6,516,204
6,561,851 6,653,979 6,697,030 6,785,830 6,845,249
6,847,830 6,876,697 6,879,585 6,886,049 D442,170
D459,303 and other patents pending.
Manufactured or sold by Sierra Wireless or its licensees under
one or more patents licensed from InterDigital Group.
Licensed under the following Nortel Networks Limited
patents:
United States patent numbers: 5128925, 5398247
France patent numbers: 2665993, 2653959, 2659812, 2745091
© 2005 Sierra Wireless. All rights reserved.
AirCard and “Heart of the Wireless Machine” are registered
trademarks of Sierra Wireless.
Sierra Wireless, the Sierra Wireless logo, the red wave design,
the red-tipped antenna, and Watcher are trademarks of Sierra
Wireless.
Windows®is a registered trademark of Microsoft Corporation.
Other trademarks are the property of the respective owners.
2 2130309

Preface
Contact
Information Sales Desk: Phone: [phone]
Hours: 8:00 AM to 5:00 PM Pacific Time
e-mail: [email protected]
Technical Support: e-mail: [email protected]
Web: www.sierrawireless.com/
developers
Post: Sierra Wireless, Inc.
13811 Wireless Way,
Richmond, BC
Canada V6V 3A4
Fax: [phone]
Web: www.sierrawireless.com
Your comments and suggestions on improving this documen-
tation are welcome and appreciated. Please e-mail your
feedback to [email protected]. Thank you.
Consult our website for up-to-date product descriptions,
documentation, application notes, firmware upgrades, trouble-
shooting tips, and press releases:
www.sierrawireless.com
Rev 3.2 Oct.05 3

MP 700 Series GPS AT Command Reference
4 2130309

Table of Contents
About This Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Terminology and acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Currency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Upgrading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Document Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Modem Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
GSM, GPRS, and EDGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Establishing a communication session. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Host connection basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Hardware structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Host and network connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Modem modes, states, and conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Connection Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
State Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Command to data state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Data to command state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Modem Buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Command buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Data buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Command Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Concatenation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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MP 700 Series GPS AT Command Reference
Responses and Result Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Possible result codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Human vs. machine interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Response and Result Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Response framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Result code framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
GPS data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Command Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Command Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Standard Modem Commands (V.25ter) . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
GSM Voice and Circuit-Switched Data Commands (GSM 07.07) . . . . . . 26
SMS Commands (GSM 07.05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
GPRS Packet Data Commands (GSM 07.07) . . . . . . . . . . . . . . . . . . . . . . . 28
EDGE Data Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Modem Control Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Command Reference Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Result Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Basic Result Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Factory Default Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6 2130309

1: About This Guide 1
• Introduction
• References
• Currency
• Document Structure
• Conventions
Note: For additional background
on the use of modems and AT
commands generally you may
consult the University of
Manitoba web site at:
www.umanitoba.ca/campus/acn/
remote/faq/at-cmds.html.
Introduction
This reference details the Attention (AT) command set
supported by the MP 700 Series GPS rugged wireless modem.
You should be familiar with the use of AT commands with
standard wireline modems to use this document.
The Sierra Wireless GSM products present two methods of
controlling the modem: AT commands and CnS (Control and
Status) language. Some features or capabilities of the modem
require the use of CnS. This document presumes that the AT
interface is the only interface available to you; features
requiring CnS are not discussed.
References
This guide covers only the command set used by the
MP 700 Series GPS and does not deal with operational use.
Refer to the product documentation for instructions on using
your modem.
Not all commands include detailed descriptions. Commands
are implemented to be compliant with industry standards and
reference is often made to the following standards:
• IS-131 (Data Transmission Systems and Equipment -
Extensions to Serial Asynchronous dialing and Control)
• EIA/TIA-592 (Asynchronous Facsimile DCE Control
Standard, Service Class 2)
• EIA/TIA/IS-134 (Amendments to TIA-592 to Support T.30-
1993 (Facsimile protocol standard))
Electronic copies of these standards can be purchased at the
ANSI Electronic Standards Store at: webstore.ansi.org. ANSI
Customer Service will respond to inquiries about standards
information at: [email protected].
Requests for hard copies of standards should be directed to the
Global Engineering Documents Division of Information
Handling Services:
voice: 800-854-7179 or 303-397-7956
Rev 3.2 Oct.05 7

MP 700 Series GPS AT Command Reference
Note: For additional background
on the use of modems and AT
commands generally you may
consult the University of
Manitoba web site at:
www.umanitoba.ca/campus/acn/
remote/faq/at-cmds.html.
fax: [phone]
e-mail: [email protected]
web: http://global.ihs.com
post: Global Engineering Documents,
15 Inverness Way East,
Englewood, CO 80112
Global Engineering operates offices around the world. Consult
the web site above for locations.
Other standards referenced in this document are available
through the 3rd Generation Partnership Project (3GPP) web
site at www.3gpp.org, and the International Telecommunications
Union Standards Division (ITU-T) at www.itu.int. They include:
• ETSI TS 100 916 V7.5.0 (1999-12) (AT Command Set for
GSM Mobile Equipment)
• V. 2 5 ter (ITU-T recommendation V.250), GSM 07.07, and
GSM 07.05 standards
• 3GPP TS 24.008: 3rd Generation Partnership Project; Mobile
Radio Interface Layer 3 specification; Core Network Protocols-
Stage 3
You may also want to consult the other documents available
on the Sierra Wireless web site at www.sierrawireless.com.
Terminology and acronyms
This document makes wide use of acronyms that are in
common use in data communications and cellular technology.
Our Internet site provides a Glossary (document #2110032)
that may be helpful in understanding some acronyms and
terminology used in this guide.
Currency
This document is current with version R2_2_7ap of the
MP 750 GPS firmware and version R3_1_2ap of the
MP 775 GPS firmware.
Upgrading
If your modem firmware is an earlier version, you can acquire
updated firmware from our web site
(www.sierrawireless.com) or by contacting your wireless
carrier.
8 2130309

About This Guide
Document Structure
Following this introduction is a section on basic elements
important to understanding and communicating with the
MP 700 Series GPS. This includes notes on the connection
between the host computer and the modem.
The document then presents the commands, registers, result
codes, and defaults provided in the command state of the
modem.
Commands are often termed AT commands. Hayes™ origi-
nated the convention of prefixing commands with an
“ATtention” string for wireline modems.
In addition to the commands, this document also describes the
definitions and use of status registers.
Commands are referenced in strict alphabetical order. This
facilitates searches for the syntax, parameters, and operation of
specific commands. To help locate whether or not a command
exists to perform a desired function, there are tables
organizing the commands into groups.
Descriptions of the definitions and use of status registers, as
well as a table of the factory/reset defaults, follow, along with
result codes, both numeric and verbose.
Conventions
The following format conventions are used in this reference:
• Character codes or keystrokes which are described with
words or standard abbreviations are shown within angle
brackets using a different font: such as <CR> for Carriage
Return and <space> for a blank space (spacebar) character.
• Numeric values are decimal unless prefixed as noted
below.
• Hexadecimal values are shown with a prefix of 0x, i.e. in
the form 0x3D.
• Binary values are shown with a prefix of 0b, i.e. in the form
0b00111101.
• Command and register syntax is noted using an alternate
font: ATD6045559010.
Note: The AT characters must be included before all commands,
except as noted in the reference tables.
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MP 700 Series GPS AT Command Reference
• Characters that are required are shown in uppercase;
parameters are noted in lowercase. Parameters are
enclosed in angle brackets (<i>) to indicate that they should
be replaced with a value. Optional parameters are
described in the text, and may also be enclosed in square
brackets ([<m>]) for clarity.
• Supported parameter values (either set or returned) are
described in the text.
Note: The brackets shown with parameters are not to be included in
the command string.
The default settings are noted in the command tables. Note
that these are the factory default settings and not the default
parameter value assumed if no parameter is specified. The
factory defaults are also noted in a section at the end of the
Commands chapter, on page 107.
Result Code This is a numeric or text code that is returned
after all commands (except resets). Only one result code is
returned for a command line regardless of the number of
individual commands contained on the line.
Response This term indicates a response from the modem
that is issued prior to a result code. Reading registers or
issuing commands that report information will provide a
response followed by a result code unless the command
generates an error.
See page 20 for a discussion of how the modem frames these
two elements.
In this document, responses and result codes from the modem,
or host system software prompts, are shown in this font:
CONNECT 14400
OK
10 2130309

2: Modem Basics 2
• GSM, GPRS, and
EDGE
• Modem modes, states,
and conditions
• State Transitions
• Modem Buffers
• Command Handling
• Responses and Result
Codes
• Response and Result
Framing
• GPS data format This section provides the information required to:
• Establish a communications session with the modem that
will allow you to enter AT commands
• Understand the operating modes and states of the modem
and what causes the modem to transition between them
• Understand which commands are available during
connections and which are not
• Understand how the modem’s results and responses are
framed and change the framing where required
GSM, GPRS, and EDGE
The MP 700 Series GPS operates on GSM network technology.
GSM (Global System for Mobile communications) is a type of
wireless communications network designed for mobile phones
that is widely deployed throughout the world. GPRS (General
Packet Radio Service) and EDGE (Enhanced Data rates for
GSM Evolution) are add-on data services to GSM networks.
GPRS provides a maximum data transmission speed of
56 kbps while EDGE provides a maximum data transmission
speed of 216 kbps. The MP 750 GPS supports GPRS while the
MP 775 GPS supports GPRS and EDGE service.
GPRS service has been implemented on most GSM networks
but there are a few areas (mainly rural areas in Europe) with
GSM coverage but no GPRS service. EDGE is less widely
implemented. The MP 700 Series GPS modem is primarily
designed to provide GPRS/EDGE data connections but the
modem can also be configured (using the Fallback feature) to
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MP 700 Series GPS AT Command Reference
establish CSD (Circuit-Switched Data) connections in areas
that have GSM but no GPRS/EDGE service (assuming CSD is
supported by your service provider).
Establishing a communication
session
Any terminal emulation program can be used to create a
communications session that will allow you to issue AT
commands to the modem. This section describes how to use
HyperTerminal, a program typically installed with Windows,
to establish a session with the modem.
To establish the communications session:
1. If the modem is not already connected to a serial port on
your computer, connect it.
2. If open, close Watcher (or any other program that commu-
nicates with the modem).
3. Launch HyperTerminal. (Depending on your version of
Windows and how it was installed, you can launch the
program by selecting Start > Programs > Accessories >
Communications > HyperTerminal.)
4. Enter any name and select any icon in the Connection
Description window and click OK.
5. Select the COM port to which the modem is connected
(usually COM1) in the Connect using field, and click OK.
6. Select these port settings:
· Bits per second 115,200
· Data bits 8
· Parity None
· Stop bits 1
· Flow control Hardware
Click OK.
To verify that the communications session is functional, enter
AT. The modem should respond with OK.
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Modem Basics
Host connection basics
Hardware structure
The MP 700 Series GPS has two main components: the
AirCard® wireless network card and the controller board.
Each of these components has its own firmware (resident
software). There is a serial link between the AirCard and the
controller board.
All AT commands that begin with AT!MP are handled by the
controller board and all others are handled by the AirCard.
It is important to recognize these two command types because
during modem-to-network connections, the MP 700 Series GPS
does not respond to AirCard AT commands. (That is, only
AT!MP commands will work.) This means that it is not possible
to, for example, check the signal strength using the command
AT!RSSI? during a modem-to-network connection.
Host and network connections
When the MP 700 Series GPS is used to access Internet services
or retrieve data over a VPN connection, two connections are
required: the host-to-modem connection and the modem-to-
network connection.
Modem-to-network
connection
Host-to-modem
connection
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MP 700 Series GPS AT Command Reference
Note: If you are developing a
network application to control or
monitor MP 700 Series GPS
modems installed in a fleet of
vehicles, it is usually best to use
Always On mode. (With On
Demand mode, it can be difficult
to track the modems’ IP
addresses.)
Note: The AT command
AT!MPOPMODE is used to set
the operating mode.
Modem-to-network connection
The operating mode determines how the modem-to-network
connection is established. In Always On mode, the modem-to-
network connection is established whenever the modem is
powered and GPRS/EDGE service is available. In On Demand
mode, the modem-to-network connection is established only
when the host-to-modem connection is requested.
Regardless of the operating mode, the modem-to-network
connection is established as needed, if the modem has been
configured to send MTP data. (See the AT!MPMTCONF
command on page 50.)
Host-to-modem connection
The MP 700 Series GPS supports serial and USB host connec-
tions. To issue AT commands to the modem, the serial
connection is required. Having a USB connection in addition to
the serial connection has two main advantages:
• USB provides a higher data rate between the host and the
modem
• With a USB connection, the modem connects instantly to
the network on startup. With only a serial connection, you
must establish the connection using Watcher or Windows
DUN (Dial-Up Networking.) With a USB host connection,
and the operating mode set to Always On, it is not necessary
to run Watcher or DUN to make connections.
If you intend to have both a serial and USB connection, you
must install the modem using the USB option. (When you
install the modem software, you are prompted to indicate
whether you are using a serial or USB connection. When you
select the USB option, both the serial and USB drivers are
installed.) If you install the modem using the serial option and
then connect a USB cable, the host computer will not be able to
communicate with the modem.
Modem modes, states, and
conditions
This document uses the words mode (circuit-switched data,
packet-switched data, fax, or voice), state (command or data), and
condition (online or offline) to describe the modem’s operational
status.
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Modem Basics
Connection Modes
The MP 700 Series GPS operates in three modes:
Circuit-switched data (CSD) In Circuit Switched Data
(CSD) mode, the modem operates much like a landline
modem.
The Fallback feature must be configured to allow for this type
of connection. (See !MPFBSETUP on page 41.)
Packet-switched data In this mode the modem establishes a
high-speed packet data connection using GPRS or EDGE service.
Voice If your account allows for it, you can attach a headset to
your modem and use it as a mobile phone. You require a 4-wire
headset with a 2.5 mm connector, to use your modem as a phone.
(This plugs into the Audio connector on the back of the
modem. You may need an extension cable if the modem is
installed in the trunk. Contact your service provider to
determine what extension cables are supported.)
States
The modem’s state indicates what form of communication is
occurring between the modem and the host computer.
At any time the modem is in one of two states:
Command The modem exchanges data with the host
computer as AT commands and replies. During voice commu-
nications the modem is always in command state.
Data The modem exchanges computer data with the host.
Note: The modem cannot be in voice mode and data state. Even
while off-hook with a voice call active, the modem still communicates
over the serial connection in command state. Commands can be
issued and executed while a voice call is in progress.
Conditions
The modem’s condition indicates whether there is a network
connection (airlink). At any time, the modem is in one of two
conditions:
Online Actively connected to a remote terminal or network
(off-hook). In the online condition, the modem can either be in
command state or in data state.
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MP 700 Series GPS AT Command Reference
Note: A transition to command
state from data state does not
require that the session be
closed. This means that DCD will
remain asserted while the
modem is in command state,
online condition.
Offline Disconnected from any remote terminal or network
(on-hook). While in offline condition, the modem can only be
in command state (without an airlink).
The following tables show the possible combinations of
modes, states, and conditions:
Table 2-1: Functional combinations of modem state
and mode
Command State Data State
CSD Mode Yes Yes
GPRS Mode Yes Yes
Voice Mode Yes No
Table 2-2: Functional combinations of modem state
and condition
Command State Data State
Online Condition Yes Yes
Offline Condition Yes No
State Transitions
The auto connect feature (see !MPPADSETUP on page 54) deter-
mines what state is established when the modem is powered:
• If autoconnect is enabled, on start-up the modem is in data
state. (A PAD session is established, but not necessarily an
Internet connection.)
• If autoconnect is disabled, on start-up the modem is in
command state.
Command to data state
The modem changes from command to data state when a
session is opened either by dialing a connection, or by
answering a data call. When a session opens, the modem
issues the CONNECT message and, depending on the DCD
setting (see page 58), asserts the DCD control signal.
Data to command state
The modem changes from data to command state when:
• The DTR de-asserts (depending on settings made, &D1 or
&D2).
• The modem is reset or power-cycled (if autoconnect is
disabled).
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Modem Basics
• If there is an active PAD (Packet Assembler/Disassembler)
session and the PAD is configured to use TIES (Time
Independent Escape Sequence), the modem switches to
command state on receipt of “AT+++”. (The “AT” must be
in upper case.) The command !MPPADCONF (described
on page 52) is used to enable and disable TIES.
When the modem changes to command state, it will issue an OK
result. This may be preceded by another result (such as NO
CARRIER) to indicate that the session was closed by an event
outside the modem. The modem returns to command state when
a session is closed.
Modem Buffers
Communication between the host and modem is buffered
based on the modem’s state.
Command buffer
When in command state, the modem buffers the input from
the host until a <CR> is entered. The buffered data can be
edited using the backspace <BS>. The modem (unless Echo is
enabled) echoes the sequence <BS><space><BS> for human
readability.
There is a limit of 200 characters to one command line,
including the AT prefix and the <CR> termination (i.e. 197
characters of useful command buffer). If the command buffer
length is exceeded the modem will continue to echo input
(which is not buffered) until the <CR> is received. When the
<CR> is entered, the modem returns the ERROR result code
without executing any commands in the line. Once over the
limit, the <BS> will not bring you back under the limit; the
ERROR code is still returned.
The command buffer is distinct from the data receive and
transmit buffers. The command buffer retains the contents of
the last issued command until the AT command prefix is
received for the next command. This allows repeating of the
last issued command by entering A/.
Data buffers
Data being transmitted or received is buffered in several ways
depending on the mode and nature of the connection. Some
caution must be taken when disconnecting to ensure that any
buffered data in the modem has been properly processed prior
to breaking the connection.
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MP 700 Series GPS AT Command Reference
Note: When concatenated
together, AT commands may not
function predictably. It is best to
avoid concatenating commands
without first testing and verifying
the results.
Specific settings for buffer controls are described in the
relevant commands and registers. Normal configuration of the
modem will not require you to adjust these settings.
Data flow control The modem’s CTS and RTS lines control
data flow. Where large amounts of data are being exchanged,
local hardware flow control must be used to prevent buffer
overflows; it is required for PPP connections. Hardware flow
control is enabled by default. (See the +IPR command on
page 98).
Command Handling
AT can be issued as a command without parameters. It acts like
a “ping” to the modem and always gives a result code of OK
(unless quiet mode is enabled).
Commands are not case-sensitive; they may be entered in
upper or lower case, or a combination. Arguments to
commands may be case-sensitive.
Concatenation
More than one command can be included in a single line,
although some commands or their parameters must be placed
at the end of the line. When concatenating commands, a space
between basic commands is optional. Where extended
commands (those beginning with a non-alphabetic character
after the AT) are concatenated, they must be separated by a
semicolon (;).
Commands are executed in the order entered. If a command
results in the ERROR result code the balance of the command
line is ignored. Only one result code is returned for the entire
command line. The complete concatenated command string
must not exceed the 200-character command buffer limit. (See
page 17).
Parameters
Most AT commands support one or more parameters, usually
a number. Allowed values are specified in this reference.
Commands that normally accept a single numeric option
switch ([<n>]) and are issued without that parameter will
assume a value of zero (0).
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