Rockwell RCV144ACx, Command Reference Manual, Page: 39 / 186

AT Command Reference Manual
1048 3-21
3.2.4 AT% Commands
%En - Enable/Disable Line Quality Monitor and Auto-Retrain or Fallback/Fall Forward
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.
%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 n = 0, 1, or 2.
ERROR Otherwise.
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 (RC288) or V.32 bis/V.32 (RC144)
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.32 bis 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.
%L - Line Signal Level
Returns a value which indicates the received signal level. The value returned is a direct indication (DAA dependent) of the
receive level at the MDP, not at the telephone line connector. For example, 009 = -9 dBm, 043 = -43 dBm, and so on.
Result Codes:
OK
%Q - Line Signal Quality
Reports the line signal quality (DAA dependent). Returns the higher order byte of the EQM value. Based on the EQM value,
retrain or fallback/fall forward may be initiated if enabled by %E1 or %E2.
Example:
AT%Q
015
Result Codes:
OK If connected.
ERROR If not connected, or connected in 300 bps, V.23, or fax modes.