1756-EN2TR communication error

[mkab 0]

Presently we are using 1756-EN2TR modules for the communication, upto now plant was running without any issue but recently we have started to experience 1756-EN2TR communication failure , Due to the communication failure one of the analog channel is showing high value during the comms failure and hence plant is getting trip. We have replaced EN2TR but still no luck so i'm not sure about real issue.

I will really appreciate help on the above issue. Thanks   

[Ken Roach 194]

If you are experiencing communication failures, you should condition your logic using the connection status of the remote I/O devices so that a "stale" value will not cause your system to malfunction.    I generally use a GSV instruction to read the EntryStatus value for a remote I/O module.

 

"Communication failure" is too general a complaint to diagnose.    Is the 1756-EN2T module firmware crashing ?   Is it losing connection to only one remote device ?  What is that remote device ?  Do you have any diagnostic ability on the switch ports or devices ports to determine if you have a cable or noise problem ?