Rockwell Automation Publication 1756-UM535D-EN-P - November 2012 29
Design an Enhanced Redundancy System Chapter 2
Controllers in Redundant Chassis
Remember these points when placing controllers in the redundant chassis pair:
• Controllers are typically included, but not required, in enhanced
redundancy systems.
• The differences between controller types are described in this table.
• You can place up to two controllers in the same chassis. When you use two
controllers in the same chassis, they must be of the same product family.
For example, you cannot place a1756-L6x controller and a 1756-L7x
controller in the same chassis.
• You can use different catalog numbers from the same product family in the
same chassis. For example, you can use two 1756-L6x controllers in a
chassis.
• Each controller must have enough data memory to store twice the amount
of tag data associated with a redundant controller project.
Table 5 - Controller Features
Feature 1756-L7x Controllers 1756-L6x Controllers
Clock support and backup used for
memory retention at powerdown
Energy Storage Module (ESM) Battery
Communication ports (built-in) USB Serial
Connections, controller 500 250
Logix CPU (processor) Dual-core Single-core
Memory, nonvolatile Secure Digital (SD) card CompactFlash card
Status display and status indicators Scrolling status display and four
status indicators
6 status indicators
Unconnected buffer defaults 20 (40, max) 10 (40, max)
When using a ControlLogix enhanced redundancy system, revision
16.081 or earlier, you cannot use two 1756-L64 controllers in the same
chassis. You can, however, use a 1756-L64 controller in the same
chassis as a 1756-L61, 1756-L62, or 1756-L63 controller.
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