Multitech MMH900, User Manual

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Appendix J - Internal MMH2834 Composite Link Modem Commands
J.1.8 Error Correction Commands
You can use AT commands to place your MMH2834 one of three V.42 (error
correction) modes of operation.
V.42 Mode Select The V.42 standard implements both MNP Class 3 & 4 and LAP-M
error correction methods. The V.42 Mode Select command (#L)
#L selects which type of error correction (MNP or LAP-M) your
MMH2834 uses for transmissions.
The various #L command options are as follows.
#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 In Auto-Reliable mode, the modem is given four seconds to
Buffering establish a Reliable connection. After this four-second period,
the modem drops to Normal mode.
$A 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.