PLC 5/03 fault blinking

Hi,
I have an experience in my plant.our PLC AB SLC 5/03 sometimes become faulty with the led flashing.Can somebody tell me what happened?Can SCP causing faulty,especially when analog input become minus(-)(below 3277 INT)?
Please give me a direction..

Go online with the processor when it is in the faulted condition and click on "Processor Status" then click on the error tab and tell us what the error code and description is.

If you think the "SCP" instruction is causing the problem then check for limits before executing the instruction.

See picture..

and yes, if a value has a overflow, the SLC geoes into fault mode. Depending on the scale factors of your SCP, that could happen.