PLC5 Multihop IP Address Dissapearing

I have a PLC5/40E that is reading a few FLOATs from a CompactLogix L35E. For some reason, twice over the last 24 hours, the IP address from the Multihop settings has dissapeared, resulting in the MSG instruction erroring out, with error code d3 (you formatted the control block incorrectly). When I go to the Multihop tab, instead of the correct IP, there's what looks like "lh" in its place.

This has happened twice now, both when no programming staff was on site, so I know for a fact this is happening on its own accord. We have added another message instruction to the PLC5 recently, but nothing directly related to this instruction has been changed. Has any one seen anything like this before? Any ideas where I should start looking to troubleshoot?

Thanks in advance!

Photo of the error code: https://i.imgur.com/mQefL7H.jpg

The Multihop settings while erroring: https://i.imgur.com/lIqTqfR.jpg

The correct Multihop settings: https://i.imgur.com/3MgohiP.jpg

As a temporary measure, I have moved the CompactLogix - > PLC5 communication to a write MSG in the CompactLogix, instead of a read MSG in the PLC5. Working so far, but time will tell.

Interesting, how did you correct it every time? Did you contact Rockwell on it?

harryting said:

Interesting, how did you correct it every time? Did you contact Rockwell on it?

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All I did to correct it was edit the IP address in the Multihop tab of the MSG instruction. As soon as the IP was correct, the MSG would complete successfully. Haven't reached out to Rockwell yet, but I likely will in the near future.

An Ethernet message in PLC-5 requires two contiguous elements in the MG file (e.g., MG100:0 and MG100:1) even though you only enter the first one into the instruction. You may want to check if the second one is being used elsewhere.

Mispeld said:

An Ethernet message in PLC-5 requires two contiguous elements in the MG file (e.g., MG100:0 and MG100:1) even though you only enter the first one into the instruction. You may want to check if the second one is being used elsewhere.

Click to expand...

Thanks a bunch! I'm thinking this was the issue. The additional messaging we added used the element directly after this one in the MG file. We have very limited PLC5 ethernet communication, so this is something I wasn't aware of. Thank you!

Mispeld said:

An Ethernet message in PLC-5 requires two contiguous elements in the MG file (e.g., MG100:0 and MG100:1) even though you only enter the first one into the instruction. You may want to check if the second one is being used elsewhere.

Click to expand...

I believed it is the root cause. We got the same issue before.