Multi-Tech Systems BL-Series - Manual (Page 65)

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Chapter 5 - Command Mode
Enable/Disable Auto Reliable Fallback Character $F
In Auto-Reliable mode, the modem is given four seconds to establish a Reliable connection. If a
single CARRIAGE RETURN is received from the remote modem during this four second period, the
Auto-Reliable modem assumes that the remote modem is not in Reliable mode and drops to Normal
(non-error correcting) mode. The CARRIAGE RETURN is the only character which causes the
modem to drop to Normal mode. Any other character will either be buffered or discarded.
The $F command can be used to disable this fallback-to-Normal-due-to-CARRIAGE-RETURN
feature.
The Auto-Reliable fallback character ($F) and Auto Reliable buffering ($A) commands can be used
together to cause the modem to buffer all data received up until the CARRIAGE RETURN, and then
drop to Normal mode. All data received will then be output following the CONNECT message.
AT$F0 = Do not fall back to Normal if CARRIAGE RETURN received.
AT$F1 = Fall back to Normal mode if CARRIAGE RETURN received.
The factory default is $F0.
Retransmit Count $R
If errors are received during a Reliable connection, the modem re-sends the block of data which
contained an error. With the $R0 command, if another error occurs, the block will be re-sent again.
The modem counts the number of times that a data block is re-sent. If the same block of data is
resent 12 times and still has not been received properly, the modem assumes that the transmission
line is unsuitable for transmission, and abort the connection.
This retransmit counter is disabled by the $R1 command. When the retransmit counter is disabled,
the modem keeps trying to send data and will not abort, no matter how many times the same block is
resent.
AT$R0 = Disconnect if retransmit count is exceeded.
AT$R1 = Do not disconnect due to retransmits.
The factory default setting is $R0.
V.42 Error Correction/300bps $E
At 300 bps, error correction is not typically used. $E1 lets the modem function at 300 bps in either
Normal (&E0), Auto-Reliable (&E1) or Reliable (&E2) mode. $E0, which is the modem’s default,
disables 300 bps/V.42 error correction altogether.
AT$E0 = No V.42 Error correction at 300 bps.
AT$E1 = V.42 Error Correction at 300 bps.
The factory default setting is $E0.