程序中断后便不可返回

[smileme]

org 000h
ljmp start
org 000bh
ljmp delaytime
org 1000h
start: mov r1,#6
mov sp,#5fh
mov r0,#7fh
again:
mov a,#0ffh
mov p1,a
wait: jb p1.0,wait
lcall light
lcall delay
djnz r1,again
sjmp start
sjmp $
light: mov a,#10001001b
mov dptr,#8003h
movx @dptr,a
mov dptr,#8001h
mov a,r0
rl a
movx @dptr,a
mov r0,a
mov dptr,#8000h
mov a,#7fh
movx @dptr,a
ret
delay:mov tmod,#10h
mov th1,#3eh
mov tl1,#02h
setb ea
setb et1
setb tr1
mov r3,#20
repeat1:sjmp repeat1
cjne r3,#20,repeat1
ret
delaytime:djnz r3,next
mov r3,#20
next:reti

end