求C51單片機匯編語言控制兩位數碼管60秒倒計時的程序，最好能說明下思路

#include <intrins.h>

#define uchar unsigned char

#define uint unsigned int

#define seg P0

#define sw P2

int tab[]={0xC0,0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,0x80,0x90};

int dis[]={0,0};

uint X;

uchar Count=0;

uchar sec=60;

void display()

{

int a;

int m=0x01;

dis[0]=sec/10;

dis[1]=sec%10;

for(a=0;a<2;a++)

{

seg=0xff;

seg=tab[dis[a]];

sw=m;

m=_crol_(m,1);

}

}

void TINT0() interrupt 1

{

TL0=-50000%256;

TH0=-50000/256;

if(++Count==20)

{

if(sec>0)sec--;

Count=0;

}

}

void Main()

{

TMOD=0x01;

EA=1;

ET0=1;

TR0=1;

TL0=-50000%256;

TH0=-50000/256;

while(1)

{

if(sec==0)sec=60;

display();

}

}