PLC to PLC Communications Issues

J. Feldman

Member
Join Date
Sep 2021
Location
Utica, New York
Posts
16
Hi All,

I have 2 ControlLogix 5570's that are supposed to each send each other some info over Produce/Consume tags. For convenience, I'll call them PLCs 1 and 2.

Each PLC is running all related controls normally. PLC 2 is even receiving all the info from PLC 1. However, PLC 1 is NOT receiving info from 2. When I'm live in the logic, I see that PLC 1 has an I/O fault, and in the I/O Configuration Ladder, the EN2TR and 5570 for PLC 2 are flagged with a warning. I have double checked that the correct revision is in each program for both the EN2TR's and the 5570s, and that PLC 1 is looking for the correct IP for PLC 2.

Any ideas/advice on why 1 is not pulling correctly from 2 would be greatly appreciated!
 
Right click on the PLC that's showing the warning and select Properties. On the Connection tab it should give you an error code and a message.

My two wild guesses would be that the tag name is typed wrong in the consumed tag setup, or the tag that it's trying to consume was not set to produced. There are other possibilities, and the error code will probably help nail them down, but those two are my most common culprits.
 
Thanks for the pointers ASF. I found the issue: chassis size!

In PLC 1's I/O Configuration tree, PLC 2's EN2TR was configured as in the correct slot, but in a 17-slot chassis (should have been 4). Correcting that has fixed my I/O fault.
 
That would not have been my guess ! Thank you for posting that feedback and followup.

By default when you create a remote 1756 chassis in the I/O tree, there is a Rack Optimized connection to the chassis.

If you are not using any I/O from that chassis, you can set the chassis connection type to "None" and run only the Produced/Consumed Tags.
 

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