6
YML545
Appendix A: AT Command 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 value, 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.