As PIC16F877 has no priority of outer interruption requests,a method of using priority encoder 74LS148 to expand its outer interruption requests is proposed.

• 由于PIC16F 877单片机没有设置外部的中断优先级,提出了一种用74LS148优先权编码器来扩展PIC16F 877单片机的外部中断源。