流水燈-定時器延時

org 00h
start: mov r0,#8;初始化，右移次數與初始亮燈狀態
mov a, #01111111b
loop: mov p1,a
acall delay;調用延時子程序
rr a
djnz r0,loop
jmp start
delay: mov tmod,#00000001b
setb tr0
mov tl0,#0b0h ;延時50ms
mov th0,#3ch
jnb tf0,$
clr tf0
ret
end