Multi-Tech Systems MT2834MR6 manual V.42 Mode Select Command #L, 1 #L0 Command, 2 #L1 Command

Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.5V.42 Mode Select Command (#L)

The V.42 Mode Select command (#L) selects which type of error correction your MT2834MR6 will use for transmissions. The V.42 standard implements both MNP Class 3 & 4 and LAP-M error correction protocols. When you execute one of the #L commands, you instruct your MT2834MR6 how to operate with each protocol. For example, the factory default setting (#L0) tells your MT2834MR6 to negotiate the protocol with the remote modem.

The following sections detail the operation of the #Ln command.

5.5.1 #L0 Command

The #L0 command, which is the factory default, allows a pair of modems to negotiate which V.42 mode (MNP or LAP-M) will be used.

5.5.1.1Originate Mode

If both modems have LAP-M capability, the modems will use LAP-M mode. If one or both modems do not have LAP-M capability and both have MNP, the modems will use the MNP.

5.5.1.2Answer Mode

The answering modem will respond to either an MNP Link Request or a LAP-M ODP signal, depending on which is issued by the originating modem.

5.5.2 #L1 Command

The #L1 command enables MNP error correction and disables LAP-M. This command is for originate mode only. Answer mode still accepts MNP or LAP-M.

5.5.3 #L2 Command

The #L2 command enables LAP-M error correction and disables MNP. This command is for originate mode only. Answer mode still accepts MNP or LAP-M.

5.5.4 #L3 Command

In the previous 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 “Protocol Establishment” to determine parameters and 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, use the #L3 command to disable the Detection phase and go directly to Protocol Establishment. Both modems must have #L3 in effect.

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