PLC5 BTW & BTR Error Handling

[SCADA_Dude]

When performing a Block Transfer Write and Read operations from analog cards on a A\B PLC 5, is it recommended to utilize the error (ER) bit for error handling or is this really not a concern. If ER isn't utilized, I'm wondering how one would know if the board stops responding to BTR/BTW's, aside from an obvious (possibly) process excursion.

The boards in this case are in the same rack as the processor. On one hand I think this is a moot point given that most of the time if a board fails (in my experience at least); the processor faults - I am puzzled by the ER bit in this sense.

Thanks

 

[Mickey]

Yes, check it, why not?. If for no other reason to at least alarm it. See picture below.
In addition to the error bit you might also check the analog value for limits ( under range or over range)

 

[Clay B.]

The error bit can be used to help with finding the problem. It will tell you which Block transfer faulted which can be made into a log.

Example: Off shift tells you the PLC faulted out 3 times last night. You can go to the logs and see that it was this error bit that was set. Now you can narrow your search for problems.

 

[OkiePC]

I have seen both 1771-IFE and 1771-OFE2 cards fail without causing a PLC5 to fault. In those cases, it was the ER bits on the block transfers that shut down the machines safely even though the analog values were "still there" and in range.

 

[SCADA_Dude]

That would be a nice troubleshooting tool and doesn't require that much additional programming. Thanks for explaining it that way, I can convince others to see the light now.