HMS Communicator network issue

[bagged2drag 0]

Hello, 

We have a system a vendor built which utilizes a Compact Logix PLC and a peripheral piece of equipment tied in via use of an HMS communicator.  This system is also on the same network as 1 or 2 other plcs (depending what job is being run).  The 3 plcs share some handshaking signals via produced and consumed tags.  The system works just fine aside from 1 issue I don't seem to be able to resolve yet.   When we boot up the system with the HMS communicator, we are not getting any data back and forth between the PLC and the HMS communicator if either of the other 2 systems are plugged in at bootup.  Occasionally, even if the other 2 systems aren't hooked up, we also experience the same issue at bootup only.   This issue is easily rectified if we momentarily unplug the other PLC's physically.   Connection is immediately restored and works fine after.  I had looked at all settings I know to, but I don't see anything that could cause this.  I have set Unicast to disabled in the HMS device communication settings within Logix5000, thinking that it would help (which it has, as before we would often have the issue frequently when the machine was operating without the 2 additional systems hooked up).   

Any ideas what I should be looking for?

[Joe E. 236]

Only thing I can think of to check is to look at the other PLCs and make sure the HMS device isn't set up as a device in their I/O trees. If one of them takes control of it, the correct one can't.

How do you resolve it if the other 2 PLCs aren't connected at boot? You said that it sometimes happens without them there but that disconnecting them is what resolves it.

[bagged2drag 0]

Oddly, shortly after I posted this, I decided to check the other PLC program, and indeed, the HMS communicator was also configured in that PLC as well with the same communication settings.  I am guessing the machine builder just reused and modified the same plc program for the 2nd fixture.  Next time I get to tha plant. I will be uploading an update with that device removed from the configuration.

[Joe E. 236]

If it's used in the PLC program somewhere, you can just inhibit the HMS module in the PLC that doesn't need it. That way you can restore it later easily if you do need it.