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Chapter 4 - Command Mode
#L0
Command The
#L0
Command allows a pair of modems to negotiate which V.42
mode (MNP or LAP-M) will be used in their transmissions.
Originate Mode
a. If both modems have LAP-M capability, the modems use LAP-M
mode.
b. If one or both modems do not have LAP-M capability and both
have MNP, the modems use the MNP mode.
Answer Mode
a. The answering modem responds to either an MNP Link Request
or LAP-M Originator Detection Pattern (ODP) signal depending on
which the originating modem issues.
#L1
Command The
#L1
Command sets your modem to MNP error correction and
disables LAP-M. This command is for Originate mode only. In
Answer mode, the modem still accepts MNP or LAP-M.
#L2
Command The
#L2
Command sets your modem to LAP-M error correction, and
disables MNP. This command is for Originate mode only. Answer
mode still accepts MNP or LAP-M.
#L3
Command In the prior commands, the modems use a two phase process to
establish a V.42 connection (detection to establish whether the
remote modem is also error correcting, and then protocol
establishment to determine parameters and to establish the error
correction connection). If you know that the other modem is a V.42
error correcting modem, and you wish to use LAP-M, the
#L3
command disables the detection phase and goes directly to protocol
establishment. Both modems must have
#L3
in effect.
Auto-Reliable Buffering $A
In Auto-Reliable mode, the modem is given four seconds to establish a Reliable connection. After this
four-second period, the modem drops to Normal mode. Any data which is received during this period
is typically discarded. The
$A
command can be used to cause the modem to buffer (save) data that
is received during this Auto-Reliable time-out period. This data will then be output by the modem after
the
CONNECT
message.
AT$A0
= Discard data received during auto-reliable time period.
AT$A1
= Buffer data received during auto-reliable time period.
The factory default is
$A0
.
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
.