===================================================
void timer_isr (void)  interrupt 1  using 1  {
	TH0 |= 0xdc;  // reload timer 0 with 0DC00H
	cputick++;
	time();       // update realtime clock
         
}

===================================================
void time ()
/* update real-time clock  */
{
   sec100++;
   if (sec100 >= 100)       /* 100 * 10 ms = 1 s */
   {sec100 = 0;
    flag1 |= 0x05;   /* set bit 0, bit 2 */
    temp = 50;
    sec++;
    if (sec >= 60)
    {sec = 0;
     flag1 |= 0x02; /* set bit 1 */
     min++;
     if (min >= 60)
     {min = 0;
     hour++;
     if (hour >= 24)
     {hour = 0;

    }
  }
 }
}
}