Rockwell Automation Publication 1756-UM001M-EN-P - February 2012 183
Chapter 12
Redundant Systems
ControlLogix Redundancy
Overview
Redundancy provides more system availability by switching control to a
secondary controller chassis if a fault occurs in the primary controller chassis.
The redundant system switches control from the primary to the secondary when
these faults occur:
• Power loss to primary chassis
• Hardware or firmware failure of any module in the primary chassis
• A major fault in the user program on the primary controller
• Loss of communication between the primary chassis and remote
ControlNet or EtherNet/IP modules
• Disconnection of an Ethernet patch cable from an EtherNet/IP
communication module in the primary chassis
• Removal or insertion of any module in the primary chassis
• A user command that causes a switchover
Topic Page
ControlLogix Redundancy Overview 183
System Requirements 185
System Considerations 186
Build a Redundant System 188
ControlNet Considerations in Redundant Systems 188
EtherNet/IP Considerations in Redundant Systems 189
Redundancy and Scan Time 190
Additional Resources 191
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