external interrupt.asm

数字钟

LED			BIT		P1.0
LEDBUF	EQU		30H

				ORG		00H
				LJMP	START
		
				ORG		03H
				LJMP	INTERRUPT
		
START:	
				CLR		LEDBUF
				CLR		LED
				MOV		TCON,#01H		;外部中断0下降沿触发
				MOV		IE,#81H			;打开外部中断允许位（EX0）
													;及总中断允许位（EA）
				LJMP	$						;等待中断
				
INTERRUPT:
			PUSH	PSW					;保护现场
			
			CPL		LEDBUF			;取反LED
			MOV		C,LEDBUF
			MOV		LED,C
			
			POP		PSW					;恢复现场
			RETI
			END