Rockwell Automation 1756-RMxx ControlLogix Enhanced Redundancy System User Manual - Manual (Page 39)

Rockwell Automation Publication 1756-UM535D-EN-P - November 2012 39
Design an Enhanced Redundancy System Chapter 2
Assign Lowest Node Numbers to Remote ControlNet Modules
Do not assign the lowest ControlNet node addresses to ControlNet modules in
the redundant chassis pair.
If you assign the lowest ControlNet node addresses to ControlNet modules in
the redundant chassis pair, you can experience these system behaviors:
• Upon a switchover, you can lose communication with I/O modules,
produced tags, and consumed tags.
• Removing a ControlNet module from the redundant chassis can result in
lost communication with I/O modules, produced tags, and consumed
tags.
• If the entire system loses power, you can be required to cycle power to the
primary chassis to restore communication.
Set Partnered ControlNet Module Switches to the Same Address
Where ControlNet modules are used as partners in a redundant chassis pair, you
must set the node address switches to the same node address. The primary
ControlNet modules can be at even or odd node addresses.
For example, if partnered ControlNet modules are assigned to nodes 12 and 13
of the ControlNet network, set the node address switches of the modules to the
same address of 12.
Figure 6 - Example of Switch Address for Partnered ControlNet Modules
CH2 CH1 OK CH2 CH1 OK
ControlNet Module Switches