定时器查询法和定时器中断法实现LED闪烁

;2013/4/23
;延时1s闪烁
org   0000h
ajmp  start
org   30h
start:mov   r0,#20
mov   p0,#0ffh		;关灯
mov   TMOD,#00000001B
mov   TH0,#3CH        ;50ms定时
mov   TL0,#0B0H
setb  TR0
loop: jbc   TF0,next         ;TF1为1时转移
ljmp  loop
next: mov   TH0,#3CH
mov   TL0,#0B0H
djnz  r0,loop         ;r0减1不为0跳转
cpl   p0.0
mov   r0,#20
ljmp  loop
end

;2013/4/24
org 0000h
ajmp 	start
org 000bh          ;定时器0的中断向量地址
ajmp 	time0
org 30h
start:mov  p0,#0ffh
mov  TMOD,#00000001B
mov  TH0,#3Ch
mov  TL0,#0b0h
setb EA
setb ET0
setb TR0
loop: ajmp loop
time0:cpl  p0.0
mov  TH0,#3Ch
mov  TL0,#0b0h
reti               ;中断返回
end