Resetting SLC 5/03 minor error


Thread Starter



i have slc5/03 and its giving error that "a minor error bit is set at the end of scan. refer to s5 minor error bits." and when i reset error and change plc to run mode, i get the same error. please help me to reset it permanently..

Bob Peterson

In the status table there will be a place where it tells you the file and rung number where the error was generated.

This is almost always a programming error.

one answer to the problem is to program in an unlatch instruction for the minor error bit at the very end of the program so it just gets unlatched every scan so it is never on at the end of the scan. but really, you need to find the programming error and fix it.
If memory serves, some errors don't give meaningful file:rung locations, I think they just list the last rung in File 2 because they're "End of Scan" type errors. If this is the case, you'll have to arrange to selectively disable large parts of your code, to narrow down where the error is occurring.

If your code is divided up into many ladder files called with JSR's, put a unique control bit in front of each JSR. Turn them all off, switch the processor to run mode, then re-enable the JSR's till the fault recurs. The subroutine you just enable contains the error.

To locate the code within the subroutine, or within LAD2 if you haven't segmented it, place JMP's to divide and conquer till you find the culprit. Probably something stupid like a divide by zero or an overflow caused by an ADD or something. If so, put some range checking on the rung to prevent that condition and review to see if there's another error causing the fault-causing value to occur in the first place. Obviously it wasn't anticipated at development time so it may indicate another issue.
You can also check the status of the error flags at the end of each JSR (or after math instructions if it's the over flow trap bit) to isolate it if it doesn't happen immediately upon switching from program-to-run.