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$En
V.42 Error Correction at 300 bps
n = 0 or 1
Default: $E0
At 300 bps, error correction is not normally used.
$E0 disables 300 bps/V.42 error correction altogether.
$E1 enables the modem to function at 300 bps in non-error correction (&E0), autoreliable
(&E1), or reliable (&E2) mode.
$An
Autoreliable Buffering
n = 0 or 1
Default: $A0
In autoreliable mode, the modem has four seconds to establish a reliable connection, after
which the modem drops to non-error correction mode. Any data received during this period
will normally be discarded. The $A command causes the modem to buffer (store) data that
is received during the autoreliable time-out period. This data is then output by the modem
after the CONNECT message.
$A0 discards the data received during the autoreliable time-out period.
$A1 buffers data received during the autoreliable time-out period.
$Fn
Autoreliable Fallback Character Enable/Disable
n = 0 or 1
Default: $F0
In autoreliable mode, the modem has four seconds to establish a reliable connection. If a
single carriage return is received from the remote modem during this period, the
autoreliable modem assumes that the remote modem is not in reliable mode, and drops to
non-error correction mode. The carriage return is the only character that causes the modem
to drop to non-error correction mode. Any other data is either buffered or discarded.
Use the $F command to enable this feature.
You can use the autoreliable fallback character ($F) and autoreliable buffering ($A)
commands together to cause the modem to buffer all data received up until the carriage
return, and then drop to non-error correction mode. All data received is then output
following the CONNECT message.
$F0 causes the modem not to fall back to non-error correction connect if a carriage return is
received.
$F1 causes the modem to fall back to non-error correction connect if a carriage return is
received.
$Rn
Retransmit Count
n = 0 or 1
Default: $R0
If errors are received during a reliable connection, the modem re-sends the block of data
that contained an error. If another error occurs, it re-sends the block again. The modem
counts the number of times that a data block is re-sent.
$R0 causes the modem to disconnect if the same block of data is re-sent 12 times without
being received properly, on the assumption that the line is unsuitable for transmission.
$R1 causes the modem to disable the retransmit counter, so that the modem keeps trying to
send data and will not abort, no matter how many times the same block is resent. Type
AT$R0 to disconnect the modem if all attempts to re-send the block fail.
Chapter 3 - AT Commands
44
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