Rockwell Automation 1756-RMxx ControlLogix Enhanced Redundancy System User Manual - Manual (Page 153)

Rockwell Automation Publication 1756-UM535D-EN-P - November 2012 153
Program the Redundant Controller Chapter 7
Minimize the Number of Programs
When programming a redundant controller, use the fewest programs possible.
Using the fewest programs possible is especially important if you plan to
crossload data and synchronize the controllers after the execution of each
program.
If you need to crossload data at the end of each program, make these
programming considerations to minimize the crossload impact on the program
scan time:
• Use only one or a few programs.
• Divide each program into the number of routines that is appropriate for
your application. A routine does not cause a crossload or increase the scan
time.
• Use the main routine of each program to call the other routines of the
program.
• If you want to use more than one task for different scan periods, use only
one program in each task.
Figure 39 - Use of Multiple Routines (preferred) Figure 39 - Use of Multiple Programs (not
preferred)