Chapter 7: AT Commands and Registers
7-26 CSMIM-T1 Hardware Installation Guide
Auto-reliable mode (\N3) allows the modem to communicate
with remote systems which support the MNP or LAPM reliable
link and with systems that do not support the reliable link. In
auto-reliable mode, the answering modem looks for incoming
MNP or LAPM protocol characters from the remote modem. If it
detects them within approximately three seconds, it tries to
establish a reliable link connection.
When the modem is set to auto-answer in auto-reliable mode, you
can shorten this 3-second period by using the %A command with
\C2.
LAPM reliable mode (\N4) uses the LAPM reliable link to
provide error detection and automatic retransmission of data if an
error occurs. This ensures that communications between your
system and the remote system are error-free. The remote system
must also be equipped to handle an LAPM reliable link. The
modem attempts to establish an LAPM reliable link immediately
after making a connection. If the attempt fails, the modem
disconnects.
LAPM reliable mode with fallback to normal mode (\N5)
attempts to establish an LAPM reliable connection. If the LAPM
connection attempt fails, the modem falls back to a normal
connection.
LAPM reliable mode with fallback to MNP reliable mode
(\N6) attempts to establish an LAPM reliable connection. If the
LAPM connection attempt fails, the modem then tries to establish
an MNP reliable connection.
NOTE You may not want to use certain other protocols, such as HP
Block Mode, with MNP. Such protocols have particular timing
requirements that can interfere with MNP’s effectiveness.
NOTE If both modems are set to auto-reliable mode, a normal
connection or no connection could result due to noise on the
telephone line.