Logix5K / CLX 5563: Corrupted Tags or Instructions?

In a certain part of this program, we are looping through instances of a control module.

The data is stored in a UDT array of 7 elements (CM_Motor[7]).

Before the JSR to the subroutine, we set up the pointer and max limit of instances to scan:

MOV 1 CM_Index
SIZE CM_Motor[0] 0 CM_MAX

Here the index starts at 1, pulls the max number of elements in CM_Motor (7) and the subsequent logic loops through the index until CM_MAX is hit.

However, the SIZE instruction is failing to pull the size of the array into CM_Max. I've tested it, and the SIZE works on other arrays (for other CMs). I also replaced the SIZE instruction with a:

MOV 7 CM_MAX

and it worked fine. So the loop is functioning correctly, it just doesn't like the SIZE instruction.

Additionally, when I do a RSLogix Compare on the version I'm having issues with (as the Base) and a development version (as the Compare) which works fine, the CM_Motor controller tag fails to appear in the compare.

Is it possible to the controller to have a corrupted tag, or maybe the SIZE instruction for that rung was compiled erroneously?

Has anyone else run into this before?

Maybe this can help.

Thanks for the link.

However I have read the help file (in RSLogix) multiple times, and I understand well how the instruction works. That is how I know it is not doing what it is supposed to be, besides I have already established via testing that it is not working.

I have circumvented the issue, but I am just wondering if anyone has encountered this before, and if it is possible for databases or rungs of instructions to become corrupted.

Export the file to an L5K, and re-import it.

This will re-create the user-program and tag databases.

If the problem persists, then the SIZE instruction must be bugged, as it says it works with structures.

Thanks for the suggestions daba.

Do you happen to know if things like this are common on ControlLogix? I've never run into this issue before.

I recently had an issue with a CLX processor where, on a save, Logix5K told me there was some tag corruption and asked if I wanted to save what it could. Generally speaking the save worked and I couldn't find anyting in the offline file that lead me to believe there was an isue. In my cse I exported to LK5 format, imported it back in to Logix5K and downloaded the result. That fixed me up.

So, yes, I have seen cases where tags get corrupted. In my case it didn't seem to affect the operation of the machine. It was also an AB-defined tag that was unhappy (a servo axis tag). Then again, it could be the tag was simply not being used.

Keith

kdcui said:

Thanks for the suggestions daba.

Do you happen to know if things like this are common on ControlLogix? I've never run into this issue before.

Click to expand...

Has re-creating the processor file fixed the problem with SIZE ?

And I have never had any issues like this in over 10 years of working with ControlLogix.

I determined that the issue was not the SIZE instruction, but the actual tag itself (a UDT). Somehow the program was having trouble executing certain instructions on it, and sometimes would not show up in a Compare of two programs.

In any case, I needed to re-download a new version to the processor and that seemed to fix the problem. I did not get a chance to try the L5K export / import technique, as it is all cGMP is this point and it would have been a big hassle, though I did delete and re-add the instruction from the rung which did not do anything. The re-download was already schedules and I figured it would resolve the issue without having to edit / delete / export things from the program.

Thanks for the suggestions.