Clgx to SLC5/03 Message Error

On a job site where we swapped out an old SLC 5/03 and replaced with a Clgx. There is another SLC 5/03 that used to message to the SLC 5/03 via Ethernet over NET-ENI module.

We have had the Clgx messaging back and forth with no issues since last Sunday. As per Murphy's law, after yet another 15 hour day and only having my head on the pillow 3 hours, the plant calls me at the hotel and all symptoms are pointing to communications errors between the 2 PLCs.

Fortunately there is an AB ethernet modem that I used to connect to the PLCs. I can go online with both the SLC 5/03 and the Clgx, but the message blocks from the Clgx to SLC 5/03 were stuck with the following error:

Only way I could resolve the issue was to reset the 1756-ENBT module and comms took off again. I was playing with network settings on the 1756-ENBT last night , trying to make the 1756-ENBT appear in Advanced IPScanner's list with a Hostname attached to the card's IP address. Any potential me messing with the card caused the comms to lock up?

That error code is "Unconnected Message Timeout". You could be swamping the 5/03 with messages being sent too rapidly.

How are you triggering the messages. It would not be good to re-trigger them as so0n as they are done - use a timer to trigger them.

I'd be tempted to put a READ message in the 5/03. you get traceability via x-ref if you use reads rather that writes. If you do put a Read MSG in the 5/03, you will have to add the tag F8 to the "Map PLC/SLC Messages" table in the "Logic" menu.

I too think it's a timing issue, like daba suggests. The CLX is a racecar compared to the unicycle it's talking to...

This typically how I do it. In trying to troubleshoot the error I placed an AFI in front of each MSG rung. Each of the 3 msg blocks had their enable bit ON and stayed ON even when I disabled the rung. Only resetting the 1756-ENBT resolved the issue. I have been online all week with the SLC 5/03 using ethernet while messaging was occuring . It was not till after I was messing with IP Scanning and Hostname of the 1756-ENBT card that the problem showed up.