Rockwell Automation 1794-L34 FlexLogix Controller System User Manual - Manual (Page 103)

103 Publication 1794-UM001G-EN-P - January 2007
Appendix
B
FlexLogix Back-Up on DeviceNet
Using This Appendix
This chapter offers a solution to back-up your FlexLogix controller on
DeviceNet. FlexLogix Back-Up on DeviceNet 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 will:
• minimize downtime in case of controller failure when the same
program is used in both programs.
• mitigate the risk of changes adversely affecting the application
(use old, proven program in one controller and new, untested
program in 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 FlexLogix Back-Up on DeviceNet 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 communications between primary and secondary
controllers determines which scanner is the master and which scanner
remains in stand-by mode.
For information about: See page
How the Back-up Works 104
Power-Up and System Start-up 106
Developing the FlexLogix Back-Up Application 108
Using Indicators to Check Status 115
Development and Debugging Tips 115