2.3
SNM15
Functional Features
Digicom SpA
MNP
3 classes of operation as well as a series of options have been
defined.
Classes 1 & 2 make use, on line basis, of an asynchronous
protocol, whereas class 3 is supported by a HDLC type
synchronous protocol.
This allows you to check the presence of errors in the transmission
blocks (due to interference present on line) and to request the
wrong blocks received to be transmitted again.
Before listing the features of the MNP supported by the SNM 15
modem, we will give a brief informative summary of the 5 levels
defined by this protocol.
MNP CLASS 1
Asynchronous error correction protocol, half-duplex or byte
oriented; it is now practically out of use with a line efficiency equal
to 70% of the nominal value of the set speed on a RS232 interface
level.
MNP CLASS 2
Asynchronous error correction protocol, full-duplex and byte
oriented with a line efficiency equal to 84% of the nominal value.
MNP CLASS 3
Synchronous error correction protocol, full-duplex and bit oriented
with a structure similar to the HDLC.
Its line efficiency is equal to about 108 of the nominal value, thus
with a total increase of 8%.