#include <AT89X51.H> //15．            定時計數器T0作定時應用技術（2
  
unsigned char code dispcode[]={0x3f,0x06,0x5b,0x4f, 
                               0x66,0x6d,0x7d,0x07, 
                               0x7f,0x6f,0x77,0x7c, 
                               0x39,0x5e,0x79,0x71,0x00}; 
unsigned char second; 
unsigned char tcount; 
  
void main(void) 
{ 
  TMOD=0x01; 
  TH0=(65536-50000)/256; 
  TL0=(65536-50000)%256; 
  TR0=1; 
  ET0=1; 
  EA=1; 
  tcount=0; 
  second=0; 
  P0=dispcode[second/10]; 
  P2=dispcode[second%10]; 
  while(1); 
} 
  
void t0(void) interrupt 1 using 0 
{ 
  tcount++; 
  if(tcount==20) 
    { 
      tcount=0; 
      second++; 
      if(second==60) 
        { 
          second=0; 
        } 
      P0=dispcode[second/10]; 
      P2=dispcode[second%10];              
    } 
  TH0=(65536-50000)/256; 
  TL0=(65536-50000)%256; 
}