Thanks Steve for your quick reply. I'm glad that the code is working somewhere. What I posted is the entire program, there is no other programming. The LED at rb3 lights up fine.

I'm assuming, first of all, that grounding the rb0 pin will result in the interrupt routine being executed (but it's not). The schematic for the picdem2+ board is available at:

http://ww1.microchip.com/downloads/e...Doc/51275b.pdf

As shown in the schematic rb0 also has an LED attached, but neither the LED nor the pullup should have any effect on the interrupt (at least as far as I see it).

What exactly do you mean by "set oscillator to XT"?

Thanks
Klaus