Publication 1756-UM523F-EN-P - December 2006
Maintain and Troubleshoot the System 123
Check the Allocation of
Unused Memory
The controller reserves a specific amount of unused memory for tags
and the rest for logic. Depending on how you configure the memory
usage, you might not have memory for the required operation.
Adjust CPU Usage for a
CNB Module
For each CNB module in a redundant chassis, keep CPU usage to less
than 75 percent.
• Each redundant CNB module needs enough additional
processing time for redundancy operations.
• At peak operations such as synchronization, redundancy uses an
additional 8 percent (approximately) of the CPU of the CNB
module.
• A total CPU usage that is higher than 75 percent may prevent a
secondary chassis from synchronizing after a switchover.
To reduce the CPU usage of a module, take any of these actions:
• Change the network update time (NUT) of the ControlNet
network (Typically, increase the NUT to reduce the CPU usage
of a CNB module.)
• Increase the requested packet interval (RPI) of your connections.
• Reduce the number of connections to (through) the CNB.
• Reduce the number of MSG instructions.
• Add another CNB module to each redundant chassis.
If Then Important
You are unable to perform online edits
OPC communications error or fail Make sure the slider is not all the way to Tags. You are able to change this setting only
while:
• offline.
• online in program mode.
You are unable to create tags while online Make sure the slider is not all the way to Logic.
To display this dialog:
1. Choose Edit ⇒ Controller Properties.
2. On the Redundancy tab, choose the Advanced button.
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