Chapter 1 – AT Commands, S-Registers and Result Codes
Multi-Tech Systems, Inc. SocketModem MT5600SMI/MT5656SMI Reference Guide (S000306C)
29
Command:
%E
Enable/Disable Line Quality Monitor and Auto-Retrain or
Fallback/Fall Forward
Description:
Controls whether or not the modem will automatically monitor the line
quality and request a retrain (%E1) or fall back when line quality is
insufficient or fall forward when line quality is sufficient (%E2). The
parameter value, if valid, is written to S41 bits 2 and 6.
If enabled, the modem attempts to retrain for a maximum of 30 seconds.
Fallback/Fall
Forward.
When %E2 is active, the modem monitors the line
quality (EQM). When line quality is insufficient, the modem will initiate a
rate renegotiation to a lower speed within the V.34/V.32 bis/V.32 (RC336)
modulation speeds. The modem will keep falling back within the current
modulation if necessary until the speed reaches 2400 bps (V.34) or 4800
bps (V.32). Below this rate, the modem will only do retrains if EQM
thresholds are exceeded. If the EQM is sufficient for at least one minute,
the modem will initiate a rate renegotiation to a higher speed within the
current modulation speeds. The rate renegotiations will be done without a
retrain if a V.32bis connection is established.
Speeds attempted during fallback/fall forward are those shown to be
available in the rate sequences exchanged during the initial connection.
Fallback/fall forward is available in error correction and normal modes, but
not in direct mode or synchronous mode with external clocks.
Default:
2
Defined Values:
%E0 Disable line quality monitor and auto-retrain.
%E1 Enable line quality monitor and auto-retrain.
%E2 Enable line quality monitor and fallback/fall forward. (Default.)
Result Codes:
OK
Otherwise ERROR
Command:
%U
Select µ-Law or A-Law Codec Type
Description:
Selects µ-Law or A-Law codec type for V.90 and 56K modulation.
This command also stores the selected setting directly to NVRAM.
Default:
Default value is country specific
Defined Values:
0
Selects µ-Law.
1
Selects A-Law.
Result Codes:
OK
Otherwise ERROR
Command:
B
Communication Standard Setting – CCITT or Bell
Description:
When the modem is configured to allow either option, the modem will
select Bell or CCITT modulation for a line speed connection of 300 or 1200
bps. Any other line speed will use a CCITT modulation standard. The
parameter value, if valid, is written to S27 bit 6.
Default:
B0 (default for MT5600SMI)
B1 (default for MT5656SMI)
Defined Values:
B0 Selects CCITT operation at 300 or 1200 bps during Call
Establishment and a subsequent connection. (Default.)
B1 Selects BELL operation at 300 or 1200 bps during Call
Establishment and a subsequent connection.
Result Codes:
OK
Otherwise ERROR
