《求助》基于51单片机的拖尾灯

#include<reg52.h>
#define uint unsigned int
#define uchar unsigned char
uchar abit=16; //流到哪位
uchar atimer0_n;
uchar code abit8[9]={1,2,4,8,16,32,64,128,0};
uchar nn;
char a,b,c,d;
main()
{ TMOD = 0x11;
TL0 = 0x00;  //2.5ms
TH0 = 0xF7;
TF0 = 0;  
TR0 = 1;
EA=1;ET0=1;
while(1)
{
  a=abit;
  if(a>7||a<0)
  a=8;
  b=abit-1;
  if(b>7||b<0)
   b=8;
  c=abit-2;
  if(c>7||c<0)
   c=8;
   d=abit-3;
  if(d>7||d<0)
   d=8;

  
atimer0_n++;
if(atimer0_n==255)
atimer0_n=0;
if(atimer0_n<5)
  P1=0xff-abit8[a];
if(atimer0_n<40)
  P1=0xff-abit8[b];
if(atimer0_n<150)
  P1=0xff-abit8[c];
if(atimer0_n<255)
  P1=0xff-abit8[d];
}
}
atimer0 () interrupt 1
{
TL0 = 0x00;  //50ms
TH0 = 0x4C;
nn++;
if(nn==2)
{
  nn=0;abit--;
   if(abit==0)
   abit=16;
}
  
}