Redundant clx processors


Thread Starter


Where can I find info. on designing a system with redundant clx processors? I assume this type of app. will require 2 5555 processors ( I dont believe there is a special cpu like cnbr ).
How can two processors own the same I/O modules?
Get in touch with your local A-B office and have their PLC manager explain how the 1756-SRM (system redundancy module) works with the 1756-L55
controllers and RSLogix 5000 version 8.52. It's not a general-release product (you haven't seen it in the release notes) because it represents a branch of the development path of RSLogix, but it is a real product in production service today.

It's a lot like the way the old 1785-BCMs worked, with a high-speed fiber optic link between the SRM modules to synchronize programs and data, and the I/O network scanners (1756-CNBR) impersonating each other's node numbers. It's less work, as the SRM's take care of the crossloading behind the scenes, but it's not undertaken lightly; you can get quite serious with redundant power supplies and redundant ControlNet Media and redundant control processors.

It takes some time to crossload and qualify the processors, when you boot it the first time, but once it's up it's solid and fast. Make sure that
the I/O you use can support the redundant ControlNet logical functions, as some popular devices (like the 1203-CN1 and the 1788-CN2DN) don't support redundant type connections from PLC-5C15 hot backup or ControlLogix hot backup systems.

Ken Roach
A-B Seattle
[email protected]

Leith Tull (Rockwell at Alcoa)

Redundant ControlLogix is available and currently in use. The 2 processors reside in a 4 slot chassis each with cnb module (ControlNet Interface) and a 2 slot redundancy module (redundancy is done via dedicated fibre optic link) All I/O for the system is then remotely addressed via the cnb modules. Some consideration does need to be taken with network communications

For information contact your local rockwell automation office who will be able to direct you through to the appropriate people.

Leith Tull
Rockwell Automation Australia
West Australia Technical Support