Publication 1756-UM523F-EN-P - December 2006
104 Maintain and Troubleshoot the System
Diagnose a Switchover or
Disqualification
To find and fix the cause of an unplanned switchover or loss of
synchronization, perform this procedure when:
• an unplanned switchover happens.
• a chassis that was synchronized becomes disqualified.
Actions
• Do the 1756-CNB/D/E or 1756-CNBR/D/E modules in the
primary chassis show PwQS?
• Yes — Go to Interpret the SRM Event Log on page 109.
• No — Go to step 2.
• Does any module in the primary chassis show PwNS?
• Yes — Go to step 2.
• No — Go to step 3.
1. Use this table to troubleshoot the secondary chassis.
• Determine the CPU usage of a CNB module
• Reduce the CPU usage of a CNB module
Adjust CPU Usage for a CNB Module 123
• Store a project to the nonvolatile memory of a controller
in a redundant system
• Load a project into the controller from the nonvolatile
memory of the controller
Store or Load a Project Using Nonvolatile
Memory
126
Store an updated project and firmware to the nonvolatile
memory of the controller while the process is running
Store a Project to Nonvolatile Memory
While a Process Is Running
128
If you want to Then see this section Page
Start here.
If the secondary chassis And each communication
module in the primary
chassis
And a secondary
communication module
has a
Then
Has power Has a matching partner in the
secondary chassis
Red OK light A. Power cycle the module.
B. Replace the module if the Red
OK light keeps coming on.
Green OK light Check the 1757-SRC cable for a
proper connection.
Does not have a matching
partner in the secondary chassis
⇒ Install a matching module.
Does not have power ⇒ Restore the power.
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