B - compactlogix backup on the devicenet network, Introduction, Appendix b – Rockwell Automation 1769-SDN Compact I/O DeviceNet Scanner Module User Manual User Manual
Page 129: Compactlogix backup on the devicenet network, Appendix
Publication 1769-UM009E-EN-P - August 2009
129
Appendix
B
CompactLogix Backup on the
DeviceNet Network
Introduction
This appendix offers a solution to back up your CompactLogix controller on
the DeviceNet network. CompactLogix system backup on the DeviceNet
network is a simple, low-cost, back-up system most effective when used in
smaller applications that require fast switchovers from a primary to a
secondary controller.
This back-up solution:
• minimizes downtime in case of controller failure when the same
program is used in both controllers.
• mitigates the risk of changes adversely affecting the application (use old,
proven program in one controller and new, untested program in the
other controller). If the new untested program causes a problem, a
forced switchover can be made to the older proven program without
downloading the program again.
The CompactLogix backup on the DeviceNet network solution takes
advantage of Shared DeviceNet Mastership of Slave I/O Devices technology.
Typically, only a single DeviceNet master exists for any particular slave. With
Shared DeviceNet Mastership, two masters can exist. Heartbeat
communication between primary and secondary controllers determines which
scanner module is the master and which scanner module remains in Standby
mode.
Topic
Page
Develop the CompactLogix Backup
Application
Using Indicators to Check Status