When I think about controller redundancy, the first thought that crosses my mind is

“I better do my research, because the components have to be exact.”

If you are familiar with the redundancy setup, you know what I am referring to. Only certain models and revisions are compatible to use in a redundant configuration.

If you have never used a ControlLogix redundancy configuration, then maybe this will be a helpful guide to get you started.

Redundant System. Image by Brandon Cooper

Recommendations and Prerequisites – Before you begin:

  • Decide which version of redundant controller firmware to use. If you have an L556X version of processor, then you will be at version 20.054 or below, but if you are using an L557X controller, then you can use redundancy firmware 24.053, 30.051, 31.052 and 32.051 depending on your current preference.
  • The first thing I recommend upon choosing your revision is to print and read the release notes for the chosen revision. The release notes will give you a list of every module’s compatibility and correct firmware version that you will need to install in each module in your redundant chassis configuration.
  • Download and install Control Flash. If using redundancy version 24.053, you can use Control Flash version 14.01, but anything newer, you will need at least Control Flash version 15.01.
  • Download and Install the Redundancy Firmware Bundle and Redundancy Module Configuration Tool (RMCT). *It is important to uninstall previous versions of RMCT before installing the latest version. You will need RMCT version 8.4.1 for firmware version 30.051.
  • I also highly recommend reading Rockwell Tech Note 765961 for understanding the correct placement of .DMK files that you will need to use to update your firmware.
  • Also, you will need to understand the path of progression when updating firmware. You cannot jump from redundancy version 20.054 straight to version 30.051. You must upgrade from version 20.054 to version 24.053, then you can flash to version 30.051. There is also a path for going higher than version 30.051 that you must take, so read carefully before starting.
  • Save your existing project and make backups, then you will need to update your Studio 5000 project to the selected version. Have the project ready for download.

Basic Steps of updating your redundancy system:

  • Using the RMCT, set the “Auto Synchronization” parameter to “Never” and disqualify the secondary chassis for update
  • Update the redundancy module firmware in the primary chassis using Control Flash software
  • Update the redundancy module firmware in the secondary chassis using Control Flash software
  • Update all other module firmware in the secondary chassis using Control Flash software
  • Download the updated Studio 5000 project to the secondary controller and place in Run Mode
  • Using the RMCT, Lock the System and Initiate a Switchover
  • Update the firmware in the NEW secondary chassis using Control Flash Software
  • Using the RMCT, synchronize the redundant chassis and set “Auto Synchronization” parameter to “Always”

Reference: “1756-RM010D-EN-P from Rockwell Automation for step by step instructions for updating your redundancy system


Many times, we install systems and tend to leave them at their current revision without updating them to stay with a current release.

I tend to be in favor of staying a revision or two behind the newest release, but also, to have a stable revision that you are confident in.

This way, you deal with less software version compatibility or feature differences in the control systems across your facility. My best to you in keeping your control systems concurrent.

Written by Brandon Cooper
Senior Controls Engineer and Freelance Writer

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Brandon Cooper


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