Rockwell Automation 1756-RMxx ControlLogix Enhanced Redundancy System User Manual - Manual (Page 30)

30 Rockwell Automation Publication 1756-UM535D-EN-P - November 2012
Chapter 2 Design an Enhanced Redundancy System
• Each controller must have enough I/O memory to store twice the amount
of I/O memory used. To check the I/O memory used and available, access
the Memory tab of the Controller Properties dialog box in RSLogix 5000
software.
For more information about data and I/O memory, see Knowledgebase
Answer ID 28972.
• When you use the redundancy system update (RSU) feature to update an
enhanced redundancy system while the system continues operation, the
updated secondary controllers must provide the same or greater memory
than the primary controllers.
A secondary controller provides greater memory than the primary
controller if it is a higher catalog number, for example, a 1756-L63 primary
controller and a 1756-L65 secondary controller.
This table describes the secondary controllers to which you can upgrade,
based on the primary controller used, when using RSU.
Differences in controller types between chassis can exist only during the
system upgrade process. When you complete the system upgrade, the
controllers in the redundant chassis pair must match for the system to
synchronize.
For more information on using RSU, see Appendix C , Upgrade from a
Standard Redundancy System or to Another Enhanced Redundancy
System on page 239 .
• In an enhanced redundancy system, revision 19.052 or later, the 1756-L65
controller’s performance differs from that of the 1756-L64 controller.
Some controller operations can take slightly longer for the 1756-L65
controller to complete.
For example, in some applications the 1756-L65 controller can experience
longer scan times than the 1756-L64 controller.
Table 6 - Controller Compatibility
Primary Controller Compatible Secondary Controller
1756-L61 1756-L61, 1756-L62, 1756-L63, 1756-L64, 1756-L65
1756-L62 1756-L62, 1756-L63, 1756-L64, 1756-L65
1756-L63 1756-L63, 1756-L64, 1756-L65
1756-L64 1756-L64, 1756-L65
1756-L65 1756-L65
1756-L71 1756-L71, 1756-L72, 1756-L73, 1756-L74, 1756-L75
1756-L72 1756-L72, 1756-L73, 1756-L74, 1756-L75
1756-L73 1756-L73, 1756-L74, 1756-L75
1756-L74 1756-L74, 1756-L75
1756-L75 1756-L75