Multi-Tech Systems DT102/xx Enable/Disable Auto-Reliable Fallback Character, Retransmit Count

Appendix F - MMH2834 Modem Commands

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 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

Retransmit Count 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 MMH2834 function at 300 bps in either Normal (&E0), Auto-Reliable (&E1) or Reliable (&E2) mode. $E0, which is the the MMH2834’s default, disables 300 bps/V.42 error correction altogether.

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