怎么用XBYTE[16进制]实现秒表从0000自加1到9999？

问题遇到的现象和发生背景

模拟图

问题相关代码，请勿粘贴截图

代码有错
#include <stdio.h>
#include <REG52.H>
#include <ABSACC.H>
#define led_low XBYTE[0xf7ff] //led1与led2数码管
#define led_high XBYTE[0xefff] //led3与led4数码管
unsigned long sex=0;
unsigned int cnt = 0;
unsigned char flag=0,i=0,j=0;
unsigned char str1=0x00,str2=0x00;
void main()
{
EA = 1;
TMOD = 0x01;
TH0 = 0xFC;
TL0 = 0x67;
ET0 = 1;
TR0 = 1;
//显示1234
led_low = str1;
led_high = str2;
while(1)
{
if(flag==1)
{
flag=0;
i = sex/100;
str1 = 0x(i);
j = sex%100;
str2 = 0x(j);
/* sprintf(str1,"0x%2lld",12);
sprintf(str2,"0x%2lld",34);*/
}
}
}
void to_interrupt() interrupt 1
{
TH0 = 0xFC;
TL0 = 0x67;
cnt++;
if(cnt>=1000)
{
cnt = 0;
sex++;
flag=1;
}
led_low = str1;
led_high = str2;
}

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

display(int value)
{
char digits[4];
digits[3] = value % 10; //个位
value = value / 10;
digits[2] = value % 10; //十位
value = value / 10;
digits[1] = value % 10; //百位
value = value / 10;
digits[0] = value % 10; //千位

led_low = digits[1] << 4 | digits[0];
led_high = digits[3] << 4 | digits[4];

}
仅做思路参考，不要当成代码用