146 Rockwell Automation Publication 1756-UM535D-EN-P - November 2012
Chapter 7 Program the Redundant Controller
Continuous Task with Crossloads at Each Program End
This diagram demonstrates how programs set to crossload and synchronize at
each program-end are executed after a switchover. As is shown, the new primary
controller begins executing at the beginning of the program that was interrupted
by the switchover. This is the switchover execution that occurs if you use the
default crossload and synchronization setting for a program.
Figure 33 - Program Execution After a Switchover (crossload after each program)
Continuous Task with Varying Crossloads at Program End
This diagram demonstrates how programs set to crossload and synchronize at
varying intervals are executed after a switchover. As is shown, the new primary
controller begins executing the program that follows the last crossload and
synchronization point.
Figure 34 - Program Execution After a Switchover (no crossload after each program)
For information about how to change the point in a task where a crossload
occurs, see Changing Crossload and Synchronization Settings
on page 144.
Program 1
Program 3
Program 1 Program 2 Program 3
Crossload
Program 2
Switchover
Crossload Crossload
Primary Controller
New Primary Controller
Program 1
Program 3
Program 1 Program 2 Program 3
Crossload
Program 2
Switchover
Crossload
Primary Controller
New Primary Controller
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