Maxim Integrated 73M2901CE AT Command - Manual (Page 7)

UG_2901CE_027 73M2901CE AT Command User Guide
Rev. 2.0 7
1 Introduction
The Teridian Semiconductor 73M2901CE supports an optimized version of the industry standard Hayes AT
Command Set. The primary distinction between the Hayes AT Command Set and the 73M2901CE AT
Command Set is in the use of the & (ampersand) command. The 73M2901CE does not use the &
command. Many 73M2901CE commands relate directly to the Hayes & commands but this is not always
the case. For instance the 73M2901CE ATC[n] command is similar to the Hayes AT&C[n] command but it
is not identical. Please be aware that these differences exist.
AT commands are issued using the following convention:
AT
AT commands must be preceded by the characters “AT”. The modem uses this sequence of ASCII
characters to determine the speed and parity of the DTE. The modem expects a command or string of
commands to follow.
Command String Conventions
The command string may consist of a letter, for example F.
The command string may consist of a letter followed by a number, for example N2.
The command string may consist of an S-register set equal to a value, for example S30=4.
The command string may consist of a string of all of the above, for example FS99=1B2C1X4S30=4.
Generally the order of the commands is not significant unless S-registers are set. Refer to Section 4,
S-registers.
Enter
AT Commands must be followed by an
EXAMPLES:
ATFS99=1Y6K3C1R2S30=4 V.22bis using flow control (U.S.)
ATDT2 Go off hook and dial the number 2
ATS95+$10 Set the Caller ID enable pin
There are two exceptions to this convention, the commands A/ (repeats last instruction issued) and +++
(enter online command mode) are neither preceded by an “AT” nor followed by a “CR”, nor do they take
any arguments. They are each described under the AT Commands heading in this section.
Online Command Mode
Online command mode allows the user to issue AT commands, including setting and reading some
S-registers, while connected. After a connection has been established, and in the absence of streaming
data, one can enter online command mode and send instructions to the modem. Not all commands issued
while in online command mode will take effect immediately. Some AT commands, including S-Register
settings, will not take effect until after the connection has been broken. For instance you would not be able
to change modulation standards or from synchronous to asynchronous data while connected. In addition
values read from some S-registers while in online command mode may not accurately reflect certain states.
Entering Online Command Mode
Issue this command to the modem (neither preceded by “AT” nor followed by ): +++
Timing is critical when entering this command, enter each “+” character one after another at a steady rate. If
the modem does not respond, repeat the command adjusting the speed of the key presses.
The modem should respond with:
OK
The modem is now ready to accept AT Commands just as if it were in idle mode. The “+++” can be followed
by an AT command without waiting for the OK, so the string “+++ATS10=255O” could be sent to cause the
modem to go into the command mode change the setting of S10 and go back on line without waiting for the
modem to return the OK message.