0000dao9999.asm.asm

采用8051单片机驱动四位数码管的定时器系统。采用keil编译

    	ORG	0000H
	AJMP	main
	ORG	000BH
	LJMP	int
	ORG	0030H	


main:   

	mov 	70h,	#00	;定时器初始化9999		
	mov 	71h,	#00
	mov 	72h,	#00
	mov 	73h,	#00

	mov	r4,	#20       ;定时1s寄存
	mov 	tmod,	#01h
	mov	tl0,	#0b0h
	mov 	th0,	#3ch
	setb 	et0
	setb 	tr0
	setb 	ea
	

lll:    lcall 	display		;显示等待	
        ajmp 	lll
       
int:
	djnz 	r4,	out	;定时1s时间未到继续
	mov 	r4,	#20	;定时是时间到	
	inc	70h
	mov	a,	70h
	cjne	a,	#10,	out
	

tt0:	inc	71h
	mov	70h,	#00h
	mov	a,	71h
	cjne	a,	#10,	out

tt1:	
	inc	72h
	mov	71h,	#00h
	mov	a,	72h
	cjne	a,	#10,	out
tt2:	
	inc	73h
	mov	72h,	#00h
	mov	a,	72h
	cjne	a,	#10,	out
	ljmp	main

out:
	mov 	tl0,	#0b0h
	mov 	th0,	#3ch
	reti


display:
 	mov 	dptr,	#table     ;查表显示
	mov 	r1,	#70h
	MOV	R2,	#0EFH
	MOV	R5,	#4
TT:
        mov  	a,	@r1
	movc 	a ,	@a+dptr
	mov 	p0,	a
	mov 	p2,	r2
	acall 	delay
	inc 	r1
	mov	a,	r2
	rl 	a
	mov 	r2,	a
	djnz 	r5,	TT
   	ret
delay:  
        mov 	r6,	#4
loop1:	mov 	r7,	#250
	djnz 	r7,	$
        djnz 	r6,	loop1
	ret


 table:
	   db   0c0h,	0f9h,	0a4h,	0b0h,	99h,	92h,	82h,	0f8h,	80h,	90h

   end