User Manual

Publication 1747-UM010B-EN-P - September 2003
1-24 Overview
Role of the 1747-BSN Module
As an integral part of the backup system, the 1747-BSN modules
enable high-speed communication between the two SLC processors
and permit the secondary processor to assume control of the process.
In addition, the 1747-BSN module provides:
high-speed transfer of the data table values from the primary to
the secondary system (HSSL), to ensure that the secondary
system’s data table is a copy of the primary system’s (2K words
maximum per BSN module pair)
exchange of information on the status of the primary and
secondary systems (LSL)
automatic transfer to the secondary system of the remote input
transfer of control from the primary processor to the secondary
processor when one of the following conditions occur:
power failure or power loss
major processor fault
1747-BSN module fault
change in the primary processor’s mode from:
RUN to PROGRAM (manual switchover)
REM RUN to REM PROG
REM RUN to REM TEST
transfer of control from the primary processor to the secondary
when one of the following conditions is detected by the
secondary processor:
communication timeout in the HSSL between the two
1747-BSN modules and primary system is not updating the
remote I/O
transfer of control command from the primary 1747-BSN
substitution of equipment without interruption of the process;
that is, the faulted system can be repaired while the other system
is controlling the process
connections for remote I/O and Data Highway Plus network
(the 1747-BSN module routes the remote I/O network and the
Data Highway Plus network to the primary processor)
isolation of the systems, in order to guarantee that a fault in one
system does not affect the other
diagnostics information
remote programming capability for secondary processor. The
secondary processor is in the DH+ network
the capability of switching two communication channels (one
configurable as RIO or DH+ and one RS-232/485 for DH485)
minimal user programming impact
use of standard SLC 5/02 or later and 1746 platform