198 Rockwell Automation Publication 1756-UM535D-EN-P - November 2012
Chapter 8 Monitor and Maintain an Enhanced Redundancy System
CPU Usage
The CPU usage of the ControlNet modules must be at 80%, or less. Keeping the
CPU usage below 80% reserves enough CPU functionality for the ControlNet
module to properly facilitate a switchover.
If the CPU usage is above 80%, the secondary chassis may not be able to
synchronize with the primary chassis after a switchover occurs. In addition,
unscheduled communication may be slowed.
If you need to reduce the CPU usage of your ControlNet modules, consider
making the changes described in this list:
• Increase the Network Update Time (NUT) of the ControlNet network.
• Increase the Requested Packet Interval (RPI) of your connections.
• Reduce the amount of connections through the ControlNet modules.
• Reduce the number of messages used in the program.
Connections Used
If your ControlNet modules’ connections used are near the limits of the module,
you may experience difficulty when attempting to go online with the system or
when attempting to add modules to the system.
For information about connections available with ControlNet modules, see
ControlNet Network Requirements on page 38
.
Monitor the ControlNet Network
For most redundant applications, monitoring the status of the ControlNet
network is important for maintenance and troubleshooting purposes.
For programming samples to monitor the ControlNet network, visit the
Rockwell Automation Sample Code Library at http://
samplecode.rockwellautomation.com. Applicable sample programs include the
following:
• ME Faceplates for ControlNet Diagnostics
• ControlNet Connection and Media Status
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