Rockwell Automation 1756-RMxx ControlLogix Enhanced Redundancy System User Manual - Manual (Page 31)

Rockwell Automation Publication 1756-UM535D-EN-P - November 2012 31
Design an Enhanced Redundancy System Chapter 2
Plan for Controller Connections
Consider these conditions when planning controller connection use:
• 1756-L6 x controllers provide 250 total connections.
• 1756-L7 x controllers provide 500 total connections.
If you use the redundant controller at, or very near the connection limits, you can
experience difficulty synchronizing your chassis.
Redundancy Modules in Redundant Chassis
Two redundancy modules, one in each chassis of the redundant chassis pair,
jointly supervise the control system operating states and transitions, establishing
the framework for system redundancy. This bridge between chassis facilitates the
exchange of control data and synchronization of operations.
The redundancy modules let you commission the redundant system in a plug-
and-play manner without any programming. You connect a redundancy module
pair with the default configuration in the redundant chassis pair and set up the
redundant system.
You can establish redundancy between chassis in either of these manners:
• Inserting a redundancy module pair into two powered chassis that contain
redundancy-compliant components and redundancy-enabled application
programs, and then connecting the redundancy modules.
• Inserting and connecting the redundancy modules in two chassis and then
inserting redundancy-compliant components into each chassis.
Once the redundant chassis pair contains all desired components, including
controllers configured for redundancy, and are powered, no further tasks are
required in the redundancy modules to activate system redundancy. The
redundancy modules automatically determine the operational state of each of the
chassis pair and are ready to accept commands and provide system monitoring.
IMPORTANT You are not required to develop any programming to migrate from a
nonredundant to an enhanced redundancy system if your application meets
these conditions:
• Your application meets the points listed in
Restrictions on page 22 .
• The controller properties in your RSLogix 5000 software project has
Redundancy enabled.