main:setb p1.0
     call delay
     clr p1.0
     call delay
     ajmp main

delay:   mov 50h,#228
delayxms:mov 52h,#20         ;50h,51h,52h用于延时  50h为参数x  延时1*x ms
delaya: mov 51h,#20
        djnz 51h,$
        djnz 52h,delaya
        djnz 50h,delayxms
        ret ;延时返回