Hi Acetronics. Thanks for your reply. As I said I wanted to use Interrupt from "Change on portB", but it didnot work. I use PIC16F84 in my project so I should optimize use of pins. I defined all of pins of PORTB as output except for one of them. I connected a push button to that. It didnot work normally. Why? Can you help me? How can I do that? Have you any example of method of using Change on port B interrupt?