Hello! I am use Redundancy ControlLogix system (1756-L61)? one rack I/O and Redundancy ControlNet (CN2R series B). 1 CN2R in controller rack (main & reserve) and 2 CN2R in I/O rack in slot0 & slot 9. The problem is then I disconnect cables controlnet off from 1 or 2 CN2R in I/O rack - my DO module (1756-OB32)resets its outputs to "0" (losing connection with CN2R) from 1-2 seconds and then outputs restored (connection with another CN2R in rack).

How to prevent this situation? (resetting outputs)

Thank you,
Alex

 

The architecture you are describing is not the way ControlLogix Redundancy is designed to work.

The "R" type ControlNet modules provide media redundancy, and the two CPU racks and 1756-RM modules provide controller redundancy.

But there isn't "network path" or "network bridge module" redundancy; you're not supposed to be able to switch between two or more 1756-CN2R modules in a single I/O chassis.

I have seen systems built this way in order to attempt to fulfill a specification requirement, but that doesn't change the way the ControlLogix Redundancy system works.


When you completely disconnect the 1756-CN2R that is bridging the logical connection to the Rack Object or to an Analog module, that logical connection has to shut down.

Performing a programmatic inhibit/enable of a second logical connection is a clever programming trick, but it's not the way ControlLogix Redundancy is supposed to work.

You could configure the Output module to Hold Last State in the event of a connection failure, but that would not allow you to actually turn the Output off in the event of a "real" network failure.