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Chapter 10 − Modem Mode AT Commands, S-Registers, and Result Codes
Multi-Tech Systems, Inc. MultiConnect Serial-to-Serial Adapter User Guide (S000354A) 88
Command Detail
Command: AT Attention Code
Values: n/a
Description: The attention code precedes all command lines except for escape sequences.
Command: ENTER Key
Values: n/a
Description: Press the E
NTER (RETURN) key to execute most commands.
Command: A Answer
Values: n/a
Description: Answer call before final ring. The modem will go off-hook and attempt to answer an
incoming call if correct conditions are met. Upon successful completion of answer
handshake, the modem will go on-line in answer mode. This command may be
affected by the state of Line Current Sense, if enabled. (Most countries do not
require Line Current Sense.) Operation is also dependent upon country-specific
requirements.
The modem will enter the connect state after exchanging carrier with the remote
modem.
If no carrier is detected within a period specified in register S7, the modem hangs
up.
Any character entered during the connect sequence will abort the connection
attempt.
Command: A/ Repeat Last Command
Values: n/a
Description: Repeats the last command string. Do not precede this command with AT. Do not press
Enter to execute.
Command: Bn Communication Standard Setting – ITU-T or Bell
Values: n = 0, 1
Default: 0
Description: When the modem is configured to allow either option, the modem will select Bell or ITU-T
modulation for a line speed connection of 300 or 1200 bps. Any other line speed will use an
ITU-T modulation standard. The parameter value, if valid, is written to S27 bit 6.
B0 Selects ITU-T operation at 300 or 1200 bps during Call Establishment and a
subsequent connection.
B1 Selects Bell operation at 300 or 1200 bps during Call Establishment and a subsequent
connection.
B2 Selects V.23 half-duplex operation at 1200 bps during Call Establishment and a
subsequent connection. (V.22bis only).
B3 Disables V.23 half-duplex operation. (V.22bis only).
Command: Ds Dial
Values: s = dial string (phone number and dial modifiers)
Default: none
Description: This command directs the modem to go on-line, dial according to the string entered and
attempt to establish a connection. If no dial string is supplied, the modem will go on-line and
attempt the handshake in originate mode.
Note: If the ATD command is issued before the S1 register has cleared, the modem will
respond with the NO CARRIER result code.
Dial Modifiers
0-9
DTMF digits 0 to 9.
* The 'star' digit (tone dialing only).
# The 'gate' digit (tone dialing only).
A-D Some countries may prohibit sending of these digits during dialing (tone dialing
only)
L Redial last number. (Must be placed immediately after ATD.)