期中考试：秒表设计

#include<reg52.h>
#define LED P0
sbit KEY1 = P1^0;
sbit KEY2 = P1^1;
unsigned int i = 0;
unsigned char NUM[]={0X3f,0x06,0x56,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};
unsigned char n = 0;
void INT_T0(void)
{
    TMOD = 0X01; //打开定时器0 ，使用模式1定时
    TH0 = 0XFC;
    TL0    = 0X18; //初始值
    EA = 1;//打开总开关
    ET0 = 1;//打开中断T0开关
}
void main(void)
{    
    INT_T0();
    TR0 = 0; //定时功能打开
    while(1)
    {        
        if(KEY1==0)
        {
            TR0 = 1;
        }
        if(KEY2==1)
        {
            i = 0;
            n = 0;
        }
                    
    }
}
void time0(void) interrupt 1 
{
    TH0 = 0XFC;
    TL0    = 0X18; //初始值
    if(i < 1000)
    {
        i++;
    }
    else
    {
        LED = NUM[n];
        if(n<16)
        {
            n++;
        }
        else
        {
            n = 0;
        }    
        i = 0;
    }
}