User's Manual

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TECHNICAL MANUAL
Telit GM862 PCS
Tri Band GPRS Data Terminal System Rev.1
2.2 AT Command Syntax
GSM commands use syntax rules of extended commands.
Every extended command has a test command (trailing =?) to test the existence of the command
and to give information about the type of its subparameters. There are two types of extended
command:
- Parameter type commands which also have a read command (trailing ?) to check the current
values of subparameters.
- Action type commands do not store the values of any of their possible subparameters, and
therefore do not have a read command.
2.2.1 Command lines
The basic structure of the command lines are:
• ATCMD1<CR> where AT is the command line prefix, CMD1 is a basic command (i.e. it have
not + prefix) and CR is the command line terminator character
• ATCMD2=10<CR> where 10 is a subparameter
• AT+CMD1;+CMD2=, ,10<CR> These are two examples of extended commands (which have a
+ prefix). They are delimited with semicolon. In the second command the subparameter is
omitted
• +CMD1?<CR> This is a read command for checking current subparameter values
• +CMD1=?<CR> This is a test command for checking possible subparameter values
These commands might be performed in a single command line as shown below:
ATCMD1 CMD2=10+CMD1;+CMD2=, ,10;+CMD1?;+CMD1=?<CR>
anyway it is always preferable to separate into different command lines the basic commands (i.e.
without + prefix) and the extended commands (the ones with + prefix); furthermore it is suggested
to avoid placing several action commands in the same command line, because if one of them fails,
then an error message is received but it is not possible to argue which one of them has failed the
execution.
If command V1 is enabled (verbose responses codes) and all commands in a command line has
been performed successfully, result code <CR><LF>OK<CR><LF> is sent from the TA to the TE,
if subparameter values of a command are not accepted by the TA or command itself is invalid, or
command cannot be performed for some reason, result code <CR><LF>ERROR<CR><LF> is sent
and no subsequent commands in the command line are processed.
If command V0 is enabled (numeric responses codes), and all commands in a command line has
been performed successfully, result code 0<CR> is sent from the TA to the TE, if sub-parameter
values of a command are not accepted by the TA or command itself is invalid, or command cannot
be performed for some reason, result code 4<CR> and no subsequent commands in the command
line are processed.
In case of errors depending on ME operation, ERROR (or 4) response may be replaced by +CME
ERROR: <err> or +CMS ERROR: <err>.