i-modul Modem 336 LL
Functions
6.6
Error correction
The i-modul Modem 336 LL 3.0 masters the V.42 error correction protocol including the
Microcom Networking Protocol Levels 2/3/4 (MNP-2, MNP-3, MNP-4) and the data
throughput optimization MNP-10. The V.42 error correction includes the protocols LAPM
(Link Access Procedure for Modem) and MNP-4. LAPM is the preferred error correction.
MNP-4 is supported to maintain the compatibility with other MNP modems. Both meth-
ods determine frames to transfer net data and use CRC (Cyclic Redundancy Check) check
sums for error tests. In V.42, there is the option to have the modem identify if the partner
is a V.42 modem, a MNP modem, or a modem without error correction. The modem can
then autonomously adjust to the partner.
As default, the automatic selection of V.42 LAPM or MNP-4 or no correction is set.
Configuration with AT commands
To define the type of error correction, use the
command
AT\N<n>
To set V.42 LAPM or MNP-4 error correction
exclusively, use the command
AT\N2
Use the following command for the i-modul
Modem 336 LL 3.0 to automatically select V.42
LAPM, MNP-4, or an error-corrected connec-
tion:
AT\N3
To set V.42 LAPM error correction exclusively,
use the command
AT\N4
For the buffered mode without error correc-
tion, use the command
AT\N0
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