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Host-Based Controller Modem Data Addendum
AT Command Set June 15,
1998
6 Version 1.0 Lucent Technologies Inc.
AT Commands Reference
AT commands are issued to the modem to control the modem's operation and software configuration. AT
commands can only be entered while the modem is in command mode. The format for entering AT commands is:
TYPE: ATXn where X is the AT command and n is the specific value for that
command.
PRESS: Enter If n is omitted from a command that takes a parameter valu, the
value 0 I(zero)
is assumed.
Any command issued is acknowledged with a response in either text or numeric values known as result codes.
Table 2 lists all the valid result codes.
In the following listing, all commands and command-values accepted by the modem are shown; any entries other
than those shown cause the ERROR result code.
+++ Escape sequence
The escape sequence allows the modem to exit data mode and enter on-line command mode. While in on-line
command mode, you may communicate directly to your modem using AT commands. Once you are finished, you
may return to data mode using the ATO command.
A pause, the length which is set by the Escape Guard Time (S12), must be used before and after an escape
sequence is issued. This pause prevents the modem from interpreting the escape sequence as data.
The value of the escape sequence character may be changed using Register S2.
A/ Repeat Last Command
This command repeats the last command string entered. Do not precede this command with an AT prefix or
conclude it by pressing Enter.
A Answer Command
This command instructs the modem to go off-hook and answer an incoming call.
Bn Communication Standard Setting
This command determines CCITT vs. Bell standard.
B0: Selects CCITT V.22 mode when the modem is at 1200 bits/s.
B1: Selects Bell 212A when the modem is at 1200 bits/s (default).
B2: Unselects V23 reverse channel (same as B3 ).
B3: Unselects V23 reverse channel (same as B2 ).
B15: Selects V.21 when the modem is at 300 bits/s.
B16: Selects Bell 103J when the modem is at 300 bits/s (default).
Result Codes:
OK n = 0, 1, 2, 3, 15, 16
ERROR Otherwise
Cn Carrier Control
The modem will accept the C1 command without error in order to assure backward compatibility with
communications software that issues the C1 command. However, this modem does not support the C0
command. The C0 command may instruct some other modems not to send carrier (i.e., it puts them in a receive-
only mode).
C0: Transmit carrier always off.
C1: Normal transmit carrier switching.
Result Codes:
OK n = 1
ERROR Otherwise