ORG		00H
TICK	EQU		10000				;10000×100us=1s
T100us	EQU		256-100				;100us時間常數(shù)（12M）
C100us	EQU		30H					;100us計數(shù)單元
LEDBUF	EQU		40H			   	
LED		BIT		P1.0
LJMP	START						;跳至主程序
		ORG		000BH				;中斷子程序起始地址
T0INT:	PUSH	PSW					;狀態(tài)保護
		MOV		A,C100us+1
		JNZ		GOON
		DEC		C100us				;秒計數(shù)值減1
GOON:	DEC		C100us+1
		MOV		A,C100us
		ORL		A,C100us+1
		JNZ		EXIT				;100us計數(shù)器不為0，返回
		MOV		C100us,#HIGH(TICK)	;100us計數(shù)器為0，重置計數(shù)器
		MOV		C100us+1,#LOW(TICK)
		CPL		LEDBUF				;取反LED
EXIT:	POP		PSW
		RETI
	
START:	MOV		TMOD,#02H			;方式2，定時器
		MOV		TH0,#T100us			;置定時器初值
		MOV		TL0,#T100us
		MOV		IE,#10000010B		;EA=1，IT0=1
		SETB	TR0					;開始定時
		CLR		LEDBUF
		CLR		LED
		MOV		C100us,#HIGH(TICK)	;設置10000次計數(shù)值
		MOV		C100us+1,#LOW(TICK)
LOOP:	MOV		C,LEDBUF
		MOV		LED,C
		LJMP	LOOP
		END