Egg on face or food for thought?...
GraemeTownsend said:
...So lesson to me: create a blank MSG data type and enter from scratch. DON'T cut and paste!...
Lesson to all you mean! I would advise always creating and configuring MSG instruction instances from scratch. Too often in the past had I encountered troublesome messages after taking such shortcuts only to later realize that a fresh instance resolved the issue.
Unexpected operations, after copying and pasting MSG instruction based logic, has long been an admitted but unresolved anomaly by Rockwell Automation. They will often to always advise you to recreate MSG instructions in these situations, if the advisor is properly informed, that is.
One explanation a Rockwell contact once gave me was that the MSG instruction's configuration data does not copy and paste well. For instance, often the MSG backing tags become corrupted, hence requiring recreation of the MSG instruction instance to reestablish the backing tag references.
There's "some" percentage chance that copying and pasting MSG instruction logic will or will not cause issue. What that percentage is, I have no idea? Maybe some are just luckier than others? I just default to never doing it. If you have been doing so, and will continue to do so, then that's A-OK. At least if you've read this thread you might remember it should the need ever arise. However, for me, the fact that a modern L24 CompactLogix controller, with more recent firmware on board, is still capable of producing this anomaly, would further dissuade me from reverting to type.
GraemeTownsend said:
...And I need to wipe the egg off my face...
Don't wipe it off. Lick it off. Taste it. It is an acquired taste. It is the delectable flavour of having learned something valuable, the hard way. Enjoy it. Savour it. Then you will be sure to remember it.
Regards,
George