Message frozen on Enable

The Message block is set so that it is triggered Buy the message EN bit going to 0.
so when the message goes to DN it re-enables it. I did not right this routine but the error as reoccurred and I had to reboot the PLC again. I think I will put some timers in to control the messaging and see if that stops the fault.

The Message block is set so that it is triggered by the message .EN bit going to 0.

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This "fanning the trigger" method causes the message to execute as fast as possible, which often ends up consuming far more bandwidth than you expect on the target device.

This can appear to be "stuck on .EN" because it enables immediately after it times out. If it can't reach the target device, that timeout is 30 seconds by default.

This also suggests that the author hasn't paid much attention to her messaging logic; I've seen it most frequently where MSG instructions are all triggering simultaneously and without consideration of buffers.

I strongly prefer to use a repeating timer to trigger the MSG instruction, in addition to the XIC instruction addressed to the /EN bit, so it won't re-trigger the instruction if it's still Enabled when the timer wants to trigger it again.

The Message block does stop because the message is never sent after it stops.
and it never times out or gets an error message.
I put a heart beat in it and it stops too when the message block locks up.

If this was the only MSG in the program, I would be willing to investigate why it appears to fail in a "frozen" manner. It's not impossible that you have encountered a firmware bug.

If it's not, then you should take a step back and re-write at least this one MSG so that it doesn't use this triggering method.

There are three Messages, at first only the read and write to the SLC5/05 were effected. But then the message block to the L61S went out. I rebooted the system and all three worked for a time. I wrote the sequence so that the next message block is enabled as soon as the one before it is done That way only one bloc is enabled at any time.
The two Blocks to the SLC5/05 now refuse to come on no matter what.

I don't think the MSG outlet valve is stuck, but you could lubricate it with blinker fluid then blow it out with sailboat fuel and try again.

I also recommend against self-triggering sequences. They work as long as the conditions on the network are perfect. As soon as you start getting lost packets or message errors, they don't work the way you expect.

I strongly recommend triggering messages with a sequencer or with a timer, not with the /DN or /EN bits from itself or another MSG.

I think I got it. The original programmer had another routine with messaging 22 motors with 3 messages each. the line is only using 12 motors. so the Buffers were getting filled and over taxed. A Rockwell engineer down under hit it right off the bat when I described the symptoms I just had to find the routine that had all the message blocks in it. It appears to be working. And I learned quit a few new thing to day. so it is a good day.
Thanks for the help.

the Buffers were getting filled and over taxed

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Yup, that'll do it.


Thanks very much for the followup !

I also should mention that the 30 Messages I took out were also all faulting which contributed to problem.