Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 35)

Publication 1747-UM010B-EN-P - September 2003
Overview 1-21
Backup Concepts for the
SLC 500 System Why Use a Backup System?
The objective of any redundant system (backup system) is to improve
the amount of up-time of a machine or process by ensuring consistent
availability of that machine, and by reducing costs associated with
equipment failure. By using this backup system, you can guard your
application against shutdowns caused by the programmable
controller.
The backup option is used when you must transfer the control of the
process to a secondary system, without interrupting the
machine/process operation.
To guard against system shutdown, a backup system must provide:
•
equipment with exceptional reliability
•
automatic fault isolation
•
minimal disturbance of the process when switching from the
primary to the secondary system
Applying 1747-BSN Backup Scanner Modules to the
SLC-500 Programmable Controller
An SLC 500 system configured with 1747-BSN modules provides
high-speed backup communication and switchover of the Data
Highway Plus, remote I/O links, and RS232 channel (on 5/03 and later
processors). In this section, we
•
show a typical SLC 500 backup configuration,
•
explain how the backup system works, and
•
describe the role of the 1747-BSN module
ATTENTION
!
Backup does not protect you from faults caused by
programming errors or system timeouts because
such an error or timeout also occurs in the
secondary processor.