Thanks Sougata,

I'll have to look into the manual more and try to absorb some of the information on how to do that. I've never used interrupts before so this will be a learning experience for me. After a quick look ay the manual, I take it I can connect my square wave output from the CMOS circuit to either pin INT0 (pin 33), INT1 (pin 34) or INT2 (pin 35).I guess I'll be using the PORTB Interrupt-on-Change feature.

Anyways it's getting late here so I'll have another look tomorrow evening and see what I can come up with between the manual and the archives. When I get a better understanding of what I'll have to do to use the Interrupt-on-Change feature (which will probably take me a few days but will be time well spent) then I'll come back with some questions.

Thanks Again
jessey