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3.4
AT Commands
The modem will respond to the commands detailed below. Parameters applicable to each
command are listed with the command description. The defaults shown for each configu-
ration command are those used in the Rockwell factory profile.
A/ - Re-execute Command
The modem behaves as though the last command line had been re-sent by the DTE. "A/"
will repeat all the commands in the command buffer.
The principal application of this command is to place another call (using the Dial com-
mand) that failed to connect due to a busy line, no answer, or a wrong number. This
command must appear alone on a command line. This command should not be termi-
nated by a carriage return.
AT= x - Write to Selected S register
This command writes the value x to the currently selected S register. An S register can be
selected by using the ATSn command. All of the S registers will return the OK response if
x is a number. Some registers may not be written due to country-specific PTT limitations.
Result Codes:
OK
For all arguments.
AT? - Read Selected S register
This command reads and displays the selected S register. An S register can be selected by
using the ATSn command.
Result Codes:
OK
For all arguments.
A - Answer
The modem will go off-hook and attempt to answer an incoming call if correct conditions
are met. Upon successful completion of answer handshake, the modem will go on-line in
answer mode. This command may be affected by the state of Line Current Sense, if ena-
bled. (Most countries do not require Line Current Sense.) The operation is also dependent
upon country-specific requirements.
Bn - CCITT or Bell
When the modem is configured to allow either option, the modem will select Bell or
CCITT modulation for a line speed connection of 300 or 1200 bps according to the
parameter supplied. Any other line speed will use a CCITT modulation standard. The
parameter value, if valid, is written to S27 bit 6. (Also, see ATFn command.)
B0
Selects CCITT operation at 300 or 1200 bps during Call Establishment and a
subsequent connection. (Default.)
B1
Selects BELL operation at 300 or 1200 bps during Call Establishment and a subse-
quent connection.
Result Codes:
OK
n = 0 or 1.
ERROR
Otherwise.
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