Quote Originally Posted by Chris Barron View Post
...Sometimes, the Seconds counter increments by two instead of one, suggesting that the ISR is called twice and the TMR3 interrupt is serviced twice for only one TMR3 overflow condition.

Totally off the top of my head; are you supposed to disable the interrupt handler as soon as you enter your interrupt routine and then re-enable it before leaving?

(I forgot assembler, 1983 is a long time away from now)

Robert