Z02215
Single Chip Modem with Integrated Controller, Data Pump, and AFE
16
.
Table 3. AT Command Set
Command
Function and Description
A
Answer
The A command causes the modem to go off-hook and respond to an incoming
call. This command is issued after the modem has returned the RING result
code.
If the modems successfully complete the answering process, each returns a
CONNECT result code and enters the ON-LINE state. If no transmit carrier
signal is received from the calling modem within the time specified in S-register
S7, the modem hangs up, returns the NO CARRIER result code, and enters the
IDLE state.
If the modem is in the COMMAND state or &Q2 or &Q3 is selected then the
ERROR result code is returned. Any commands following the A command on
the command line are ignored.
This command is aborted if a character is received from the terminal before the
answer process is completed, or when DTR drops if certain options in the &Q or
&D commands have been used.
Note: North American default values are designated by bold type. The operation of these commands, and the default
values of option commands, are configurable for operation in different countries.
B
Communicat The B command specifies special telephone line modulation standards required
ion Standard for the connection. The modem can be configured to use:
Option
1 – Bell 212A instead of ITU-T V.22 at 1200 bps
2 – Bell 103 instead of ITU-T V.21 at 300 bps
3 – ITU-T V.23 or Bell 202 in data modes with receive and transmit speeds that
differ whether the caller or answerer transmits data at a higher data rate.
4 – In ITU-T V.23 data mode, Minitel line reversals.
5 – ITU-T V.23 or Bell 202T in data modes when the receive and transmit
speeds are different, and with a 4-wire telephone interface instead of a 2-wire
telephone interface
When ON-LINE in data modes with differing receive and transmit speeds (V.23,
Bell 202), the modem recognizes only the Escape Sequence (+++) and modem
commands at the higher of the speeds.
S-register S37 also contributes to the selection of the modulation standard.
This register sets the telephone line data rate, and the split rate data mode (Bell
202/ Bell 202T or V.23).
Both modems must be configured identically to prevent communication failures
caused by incompatible telephone line modulation standards.
PS001907-0904
AT Command Set
ZILOG [ ZILOG, INC. ]
