Hi Phillip,

Not a foolish question, since the kind of mistakes I make are foolish...but I double checked, and timer 0 is in mode 1. At least in the initialization code. I'd better go back to check to see what it is at the time of the fault. Maybe TMOD is getting stepped on later? That still doesn't explain though why it works most of the time.

In any case, it *is* working most of the time...and if timer 0 was in mode 3, then whenever the LSB overflowed, TF0 should have set.

I guess I still have my previous question: if I really wanted to stop TF0 from setting when the timer overflowed, would it be possible to do?

Thanks for the ideas guys, I'll keep looking at it!

Dennis