8 AT Command Reference
All modem functions are controlled using the same industry-standard AT commands that
are used to control landline modems. A knowledge of these commands is not required by
most users, but are provided here as a reference.
8.1 The Six Types Of Commands:
There are six types of AT commands as defined in the following list;
•
Basic AT Parameters
•
S-Registers
•
Basic Action Commands
•
Extended AT Configuration Commands
•
Cellular AT Commands
•
Land-Cellular Proprietary AT Commands
The parameters set by the various AT commands in this section are applied to all subsequent calls
and will be used each time you place a call. As such, your custom settings (if not saved in a
profile) will be available until you power down the modem. These settings are lost upon power-
down if not saved.
The CDM-819s also gives you automatic support of all AT commands that are unknown to the
modem but are supported by your cellular carrier’s IWF. Since the carrier may charge you for the
airtime used for this connection, the modem's auto-connect ability is disabled by default. Issue
the:
AT+CXT=1
command to enable this mode, if needed.
8.2 Command Line Syntax
A command line consists of the attention code followed by one or more commands and
terminated by an end of line code. The attention code is the character pair "
AT
" or "
at
". By
default, the end of line character is the ASCII CR character (decimal 13), unless it is changed by
the S3 command. The ASCII CR character is equivalent to one keystroke of the ENTER key.
Refer to the "S-Registers" section 10.5 for more information on this command. Spaces are
ignored (unless within quotes) and may be inserted between arguments within the AT command
line to make it more legible, if desired.
The Basic and S-Register commands may follow each other on the command line without any
separating delimiters. The Extended Format Commands (those beginning with a "+" character)
must be terminated with a semicolon ";" if they are followed by another command on the same
line. The ";" character is not required after the last command on the line.
Commands may be edited using the backspace key, but the backspace will not delete the AT
attention command at the beginning of the command line.
8.3 Result Codes
After issuing a command, a result code will typically be displayed on the screen to inform you if
the command was successful, unsuccessful, improperly formatted, etc. When in the command
mode, eight possible result codes may be returned. The result codes can be set to display as either
digits or words by accessing the Verbose command. The digit code is returned when the Verbose
mode is OFF (
V0
); the word code is returned when Verbose is ON (
V1
). See the
"Basic AT
Parameters Table"
, section 10.4 for more information on Verbose. Extended result codes may
also be returned. The result codes are listed in the following table.
