> I am writing a safety-related software and need to detect if
> an input pin gets stuck at 1 (or 0). Could any one tell me how
> to do it in the software?

"Stuck" implies the pin remains at 1 for a certain length of time,
(how long ?) so you could use the pin test to reset the timer

btfsc  pin
return
clrf  tmr1l     ;or here you could clear WDT if using WDT timeout
clrf  tmr1h

if the pin doesn't go to 0 before the timer rolls over then an IRQ
or WDT timeout is generated, or you could test tmr1if. You don't
give enough info for many more suggestions

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