User Manual

20
Modem AT Commands
Appendix A
Mini PCI User’s Guide Xircom Inc
AT Command Reference
A Answer
Typing
ATA
causes the modem to go off-hook and respond to an incoming call by generating a carrier
signal and starting the handshaking process. This must be the only command or the final command in the
command line.
If the handshaking process is successful and a connection is established, the normal
CONNECT
message
is displayed. If the carrier signal is not detected within the time specified in S-Register
S7
, a
NO
CARRIER
result code is displayed.
Bn Select Communications Standard
The
ATBn
command selects the communication standard (ITU or Bell) to be used by the modem, as
follows:
B0 Use ITU V.22 at 1200bps. B0 selects ITU V.22 at 1200bps and ITU V.21 at 300bps.
B1 Use Bell 212A at 1200bps. B1 selects Bell 212A at 1200bps and Bell 103J at 300bps.
B2 Unselect V.23 reverse channel.
B3 Select V.23 reverse channel.
B15 Selects V.21 when the modem is at 300bps (same as B0).
B16 Selects Bell103J when the modem is at 300bps (same as B1).
The ATB1 and ATB16 parameter settings are not available in some countries. Defaults are country-specific.
Break (Escape) command
See Special Commands.
Cn Carrier Control
The ATCn command, where n is 1, guarantees backward compatibility with communications software that issues the
C1 command. C0 is not supported; it may set some modems to "receive only mode."
C0 Transmit carrier always off (
not supported
).
C1
Normal transmit carrier switching.
Dn Dial A Telephone Number
The ATDn command is used to dial a telephone number. The n represents a dial
string consisting of dial digits/characters and dial modifiers (see below) and must not exceed 40 characters. Spaces,
hyphens, and parentheses can be used for clarity, but they are ignored by the modem.
The Dial command can be used for either pulse (rotary) or tone dialing. The dial digits/characters
are 0 - 9 A B C D # *. The characters A B C D and the symbols # and * represent specific tone
pairs and can be used only when tone dialing. These characters and symbols are ignored when
pulse dialing is used. Some countries restrict or prohibit the use of some of these characters.
Dial Modifiers
Dial modifiers are recognized by the modem only when they are part of a dial string following
the ATD command. Possible dial modifiers are:
L Redial Last Number
Redials last number if used as first character following ATD. Otherwise it is ignored.