sbit CS=P1^3;
sbit CLK=P1^4;
sbit DO=P1^5;
#define DataPortP3 P3
//模數(shù)轉(zhuǎn)換，時鐘下降沿，高位在前，8位精度
uchar da_value[3];//存放轉(zhuǎn)換值
uchar analog_to_digital(void)
{
  uchar i,digital_value=0;
  CS=1;
  CS=0;
  DO=1;
  while(DO!=0);//等待轉(zhuǎn)換信號
  for(i=0;i<8;i++)
  {
     if(DO)
	    { digital_value|=0x01;}
	 CLK=1;
	 CLK=0;
	 digital_value<<=1;
  }
  CS=1;
  return(digital_value);
}

void digital_to_analog(void)
{
  uchar temp,a,b,c;
  temp=analog_to_digital();
  DataPortP3=temp;
  a=temp/100;
  b=temp%100;
  c=b%10;
  b/=10;
  da_value[0]=a;
  da_value[1]=b;
  da_value[2]=c;     
}