Summary - Multitech MT2834MR Owner's Manual

PN 88300150
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.
Type AT$F0 to cause the modem to not fall back to normal connect if a CARRIAGE
RETURN is received.
Type AT$F1 to cause the modem to fall back to normal connect if a CARRIAGE RETURN is
received.
The factory default setting is $F1.
#P Parity Selection
The #P command enables the setting of Callback modem parity for the prompt message sent
by the Callback modem. AT#P0 selects no parity. AT#P1 selects odd parity. AT#P2 selects
even parity.
The factory default setting is #P0.
$R Retransmit Count
If errors are received during a Reliable connection, the modem will resend the block of data
which contained errors. If another error occurs, the block will be re-sent again. The modem
counts the number of times that a data block is resent. If the same block of data is resent 12
times and still has not been received properly, the modem will abort the connection, as
dictated by the AT$R0 command.
This retransmit counter can be disabled with the $R1 command. When the retransmit counter
is disabled, the modem will keep trying to send data and will not abort, not matter how many
times the same block is resent.
Type AT$R0 to disconnect if the retransmit count is exceeded.
Type AT$R1 to not disconnect due to excessive retransmits.
The factory default setting is $R0.
$E V.42 Error Correction at 300 bps
At 300 bps, error correction is not normally used. $E1 lets the MT2834MR to function in either
Normal (&E0), Auto-Reliable (&E1) or Reliable (&E2) mode. $E0, which is the factory default
setting, disables V.42 error correction altogether.

5.17 Summary

This chapter has covered the commands necessary for the MT2834MR to operate as a V.42 device.
Briefly, we'll summarize these sections here. If something here doesn't seem clear, now may be a good
time to refer to the appropriate section.
V.42 error correction is built into the MT2834MR's hardware, and detects virtually 100% of transmission
errors, which are usually caused by noisy phone lines. When errors are detected, the V.42 protocol
causes the modem to retransmit the errant data block.
V.42bis and MNP data compression, also built into the MT2834MR's hardware, provides an effective
throughput higher than the modem's bps transmission speed. The amount of increase depends on the
type of data being transmitted.
The MNP protocol is divided into several "classes", which for our purposes are numbered 3 through 5.
The MT2834MR uses all of these MNP classes, which yields a higher throughput and error free
transmissions. LAP-M provides another type of error correction.
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