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Chapter 5 – AT Commands, S-Registers, and Result Codes
Multi-Tech Systems, Inc. SocketModem MT5600SMI Developer’s Guide 43
Command: A Answer
Description: 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 +FCLASS command and country-specific requirements.
If +FCLASS=0 is selected, 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.
If +FCLASS=1, 1.0, or 2 is selected, the modem will go off-hook in V.21
answer mode. It will generate the V.21 2100 Hz answer tone for 3 ± 0.5
seconds and, following a delay of 70 ms, will proceed as if the +FTH=3
command were issued. At any stage up to (but excluding) the +FTH=3
command state, any character will abort the communication. (See the
description of the +FTH command for details.)
Command: H Disconnect (Hang-Up)
Description: Initiates a hang up sequence. This command may not be available for
some countries due to PTT restrictions.
Default: None
Defined Values: H0 The modem will release the line if the modem is currently on-line,
and will terminate any test (AT&T) that is in progress. Country
specific, modulation specific, and error correction protocol specific
(S38) processing is handled outside of the H0 command.
H1 If on-hook, the modem will go off-hook and enter command mode.
For US models, the modem will remain off-hook. For W-class
models, the modem will return on-hook after a period of time
determined by S7.
Result Codes: OK
Otherwise ERROR
Command: O Return to Online Data Mode
Description: Determines how the modem will enter the online data mode. If in the online
command mode, the modem enters the online data mode with or without a
retrain. If in the off-line command mode (no connection), the modem
reports ERROR.
Default: None
Defined Values: O0 Enters on-line data mode without a retrain.
Handling is determined by the Call Establishment task. Generally, if
a connection exists, this command connects the DTE back to the
remote modem after an escape (+++).
O1 Enters on-line data mode with a retrain before returning to on-line
data mode.
O2 Fast retrain without speed change (used for diagnostic purpose
only).
O3 Renegotiate rate without speed change (used for diagnostic purpose
only.
O4 Renegotiate rate down one speed (used for diagnostic purpose
only).
O5 Renegotiate rate up one speed (used for diagnostic purpose only).
Result Codes: OK
Otherwise ERROR (or if not connected)