Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 38)

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