Communication modules in redundant chassis – Rockwell Automation 1756-RMxx ControlLogix Enhanced Redundancy System User Manual User Manual
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Rockwell Automation Publication 1756-UM535D-EN-P - November 2012
Chapter 2
Design an Enhanced Redundancy System
Communication Modules in Redundant Chassis
Remember these points when placing ControlLogix ControlNet and
EtherNet/IP communication modules in the redundant chassis pair:
• You must use enhanced communication modules in enhanced redundancy
systems. Enhanced communication modules contain a ‘2’ in their catalog
number. For example, the 1756-EN2T module.
Standard
ControlNet and EtherNet/IP communication modules are not
supported.
• You can use the 1756-EN2TR module only with an enhanced
redundancy system, revision 19.052 or later.
• You can use any combination of up to seven enhanced communication
modules in each redundant chassis.
• If you use a ControlNet network in your redundant chassis pair, you must
have two ControlNet communication modules outside the redundant
chassis pair. When assigning node address numbers, assign the lowest node
number address to a ControlNet communication module outside the
redundant chassis pair.
Use at Least Four ControlNet Network Nodes
Assign Lowest Node Numbers to Remote ControlNet
.
• You cannot use Series A ControlNet communication modules in a
redundancy system.
• The Series for EtherNet/IP communication modules is not required to
match in a partnered set. However, if your application requires a feature
specific to a module series level, you must use the same series level for each
module in a partnered set.
For example, only the 1756-EN2T/C communication module only offers
the double-data rate (DDR) feature. You must use 1756-EN2T/C
modules in each chassis of the redundant chassis pair to use DDR.
• Do not use the USB ports of communication modules to access the
redundant system network while the system is running, that is, online.
Using the USB ports while online can result in a loss of communication
after a switchover.
For a list of the ControlLogix communication modules available for use in an
enhanced redundancy system, see