使用单片机制作的数字电压表

今天我们利用单片机AT89S51与ADC0809设计一个数字电压表，能够测量0－5V之间的直流电压值，四位数码显示，但是使用的元器件数目最少。C语言源程序
#include
unsigned char code dispbitcode[]={0xfe,0xfd,0xfb,0xf7,
                                  0xef,0xdf,0xbf,0x7f};
unsigned char code dispcode[]={0x3f,0x06,0x5b,0x4f,0x66,
                               0x6d,0x7d,0x07,0x7f,0x6f,0x00};
unsigned char dispbuf[8]={10,10,10,10,0,0,0,0};
unsigned char dispcount;
unsigned char getdata;
unsigned int temp;
unsigned char i;
sbit ST=P3^0;
sbit OE=P3^1;
sbit EOC=P3^2;
sbit CLK=P3^3;
void main(void)
{
  ST=0;
  OE=0;
  ET0=1;
  ET1=1;
  EA=1;
  TMOD=0x12;
  TH0=216;
  TL0=216;
  TH1=(65536-4000)/256;
  TL1=(65536-4000)%6;
  TR1=1;
  TR0=1;
  ST=1;
  ST=0;
  while(1)
    {
      if(EOC==1)
        {
          OE=1;
          getdata=P0;
          OE=0;
          temp=getdata*235;
          temp=temp/128;
          i=5;
          dispbuf[0]=10;
          dispbuf[1]=10;
          dispbuf[2]=10;
          dispbuf[3]=10;
          dispbuf[4]=10;
          dispbuf[5]=0;
          dispbuf[6]=0;
          dispbuf[7]=0;
          while(temp/10)
            {
              dispbuf[i]=temp;
              temp=temp/10;
              i++;
            }
          dispbuf[i]=temp;         
          ST=1;
          ST=0;
        }
    }
}
void t0(void) interrupt 1 using 0
{
  CLK=~CLK;
}
void t1(void) interrupt 3 using 0
{
  TH1=(65536-4000)/256;
  TL1=(65536-4000)%6;
  P1=dispcode[dispbuf[dispcount]];
  P2=dispbitcode[dispcount];
  if(dispcount==7)
    {
      P1=P1 | 0x80;
    }
  dispcount++;
  if(dispcount==8)
    {
      dispcount=0;
    } 
}