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Command Syntax
The attention or “AT” prefix is required prior to entering any command. All commands require a carriage return or
<CR> following the entry of the desired command. All command responses are encapsulated by a carriage return
and line feed or <CR><LF>. The ASCII display of these characters is suppressed with only the modem response
being presented.
In addition to terminating AT commands, the carriage return <CR> is also used to abort commands that are
executing.
Most AT commands complete immediately so there is no opportunity to abort them, for instance ATI. However,
Some commands like AT+COPS or AT+CFUN can actually take several seconds to complete. The AT command
interface is said to be in execution mode when a command is running and has not returned a result code
(OK/ERROR). A second <CR> entered while the AT command interface is in execution mode will abort the
command and return the interface to command mode.
Some AT commands require additional input, for instance AT+CMGS. After terminating the AT+CMGS command
with a <CR> the AT command interface enters line edit mode. While in line edit mode all characters are accepted
except CNTL-Z. CNTL-Z terminates line edit mode and the AT command interface enters execution mode. Like
before, at this point another <CR> will abort the command.
AT message concatenation can be done using the ; <semicolon> between commands.
The following examples demonstrate the potential usage of AT commands presented:
Type Example Description
Syntax Query AT+GXXX=? When entered will return the command format and value ranges.
Read Syntax AT+GXXX? When entered will return the current value assigned to the command.
Write Syntax AT+GXXX=<value>,<value>, When entered will set the command to specified value(s).
Execute Syntax AT+GXXX When entered will execute the specified command.
Command Concatenation AT+CRC=1;S0=1 When entered it will execute both the CRC and S0 command.