#include <at89x51.h>
#define  ADC0809BaseAdrPt (*(unsigned char *)ox7ff8)

unsigned char ADCResult[4];
unsigned char CurrentCh;
unsigned char ADCEnd=1;

void ADC_ISR(void) interrupt 2
{
 unsigned char result;
 EX1=0;
 result=*(ADC0809BaseAdrPt+CurrentCh);
 ADCResult[CurrentCh]=result;
 ADCEnd=1;
}

  void StatADC0809(void)
{ 
  *(9ADC0809BaseAdrPt+CurrentCh)=CurrentCh;
   ADCEnd=0;
   EX1=1;
}

void main(void)
{
  unsigned char i;
  EX1=1;
  IT1=0;
  EA=1;
  while(1)
   {
     if(ADCEnd)
      {
        CurrentCh++;
        if(CurrentCh>3)
          CurrentCh=0;
        StatADC0809();
       }
    }
}