SLC 5/05 Minor Error Bit

[Tim Ganz]

I have a SLC 5/05 that faulted with a S:5 minor error bit and I can't figure out what that is.

It says "A minor error bit is set at the end of the scan. Refer to S:5 minor error bit"

On the errors tab sone of the S:5 bits are high. they all have 0 in the box? I have S:5/0 through S:5/4 and S:5/11 and S:5/15

How can I find what caused this?

 

[strantor]

Probably a math overflow.

 

[daba]

As each instruction executes, it may affect the arithmetic status bits, so these will be going on and off rapidly during the scan, and there is no "memory" of these.

Math Overflow status also latches a "trap bit" S:5/0, which if still set at the end of the scan will cause the processor to go into fault mode.

IMHO it's too late to deal with the math overflow at the end of the scan, it should have been detected immediately after the instruction that flagged it, and dealt with there.

The simplest, and MOST COMMON solution, is to put a rung at the end of LAD2 with just a single OTU of S:5/0

But be aware that at least one of your math instructions is causing an overflow status to be set !!