Feature on RSLogix500

Hi All,

Through this forum, I would like to discuss with you all about feature that has on RSLogix500.What I mean is about FAULT/POWERDOWN(Rung#)S:20, (File#)S:21.(to access it, go to Controller tab-Processor status , and Error tab)
What function of this feature?
If I am not wrong, those addresses doesn't detect/mentioned automatically that there is a problem on rung or file.(let's say on Program File5, rung 25 there is a calculation that reach over 32767 that cause a overflow condition, and then processor will be fault)
I have simulated this condition with the small program with RSLogix500 and RSEmulate500, and caused the processor fault).
The message is "A minor error bit is set at the end of the scan. refer to S:5 minor error bits".
On RSLogix500, Fault/powerdown(rung#)S:20 = 50, (File#) S:21 = 2.
But the actual I have made this problem on program File5 and rung 25, not on File2 rung 50.
Any comment about it ?

Regards,

Deer

You had a MINOR error.

MINOR errors are OK (sort of). The SLC can live through a minor error. All you have to do is clear the minor error bit (most likely S:5/0 - math overflow (number greater than 32767 or less than -32768 trying to go into an N register).

You can clear the error immediately after calculation (recommededed). Some calculation almost ALWAYS cause math errors (but produce the desired results in the math registers, S:13 & S:14).

You could clear the error at the end of the subroutine that the calculation is in.

You can clear the error at the end of the program.

But you didn't. The program got to the end of the program scan, and the error was still there. Since it "knew" that it was going to hit the error next scan (and also, with the bit set, had no way of trapping any new errors), it figured that the programmer must have made a mistake, and so faulted itself.

The last rung it had scanned was 2:50, so that's where it reported the error at. If you had had an OTU S:5/0 on that rung, the SLC wouldn't have faulted, so in a sense, it DID tell you the location of the error. It just didn't tell you what you were expecting - the rung on which the minor error bit got set.

That proabably would be a good firmware change in future SLCs (and PLC-5s), but AB's been doing it this way for so long, that they are not likely to change it.

Now if you had had a MAJOR fault (like having an indirect address point to a non-existant address), then you would have been pointed to exactly the file:rung of the offending code.

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