slc503 cpu fault question

aroland said:

Hi,

The scenario:
The system has been working fine for many years. There is an intermittent issue somewhere. I have yet to look for error codes.

1) No fault.
2) Pwr down, unplug wired terminal block from NI4 or NO4I card.
3) Pwr up and immediately get flashing FLT on CPU card.
4) Pwr down, plug in TB.
5) Pwr up, no FLT, system works as desired.

Here is my question:
How does the CPU know to give a flashing FLT light when the "wired terminal block" is unplugged from the 1746-NI4 or NO4I card?
(when the wired TB is plugged in the system works as desired.)

Thanks!
Adam

Click to expand...

The multiply operation will generate an overflow bit and minor error
flag whenever the results exceed 16 bits. Since the divide is carried
out on the 32 bit result in the math register, the overflow does not
present a problem. The minor error flag has to be cleared before the
end of the program scan to avoid a system error

Click to expand...

kwade said:

What is the fault/fault code?
Analog Input:
Could be a math error(over/under-range scaling) escalating to hard fault.
(ref http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1746-um005_-en-p.pdf PG 6-21)
Analog Output card:
Does the card detect interrupted OUTPUT current?

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