The use of 8255 interface chip and ADC0809

The experiment purpose ： utilize 8255 Interface chip and ADC0809 Realize the reading of analog voltage
Experimental circuit ：

Detailed code ：

#include<reg51.h>
#include<absacc.h>
#define PA_ADDR XBYTE[0x300] //PA mouth , Segment code port 
#define PB_ADDR XBYTE[0x301] //PB mouth , Bit scanning port 
#define PC_ADDR XBYTE[0x302] //PC mouth ,AD Conversion data port 
#define CMD_ADDR XBYTE[0x303] //8255 Command port 
sbit start= P1^0;	//ADC0809 Start signal 
sbit adda= P1^1;   // Channel selection 
sbit addb= P1^2;
sbit addc= P1^3;
sbit eoc= P1^4;  // Conversion end signal 
sbit baoj=P3^1;//waring light
sbit buzz=P3^2;//warning voice 
sbit xuanzhe=P1^6;// Press the key to select the channel 

unsigned char flag=0; //50ms To the flag 
unsigned char code SEG[10]={
    0x3f,0x06,0x5b,0x4f, 0x66,0x6d,0x7d, 0x07,0x7f,
0x6f};
unsigned char code SEG1[10]={
    0xbf,0x86,0xdb,0xcf, 0xe6,0xed,0xfd, 0x87,0xff,
0xef}; 
unsigned char dispbuf[3]={
    1,1,0};  // Display 100 bits of buffer 
void Timer0_Init()		  
{
      TMOD=0x01;  // Timer 0 The way 1
   TH0=(65536-5000)/256;    // timing 5ms
   TL0=(65536-5000)%256;
   ET0=1;	   // Open the interrupt 
   EA=1;
   TR0=1; 	 // Turn on the timer 0
}


void Timer0_ISR()  interrupt 1 using 0
{
      
   static unsigned char i=0,k=0;

   TH0=(65536-5000)/256; // Reset the initial value 
   TL0=(65536-5000)%256;
   k++;
  if(k==10)  
  {
     
      k=0;
	   flag=1;	//50ms Arrival rule flag Set up 1
  }
   PB_ADDR=0xff; // Turn off all nixie tubes 
   if(i!=2)  PA_ADDR= SEG[dispbuf[i]] ;              // Sending segment code 
   else  PA_ADDR= SEG1[dispbuf[i]]  ; // The highest digit shows the decimal point 
   PB_ADDR=~(0x01<<i); // Send scanning code 
   i++;
   if(i==3)i=0;
  // }
}

void display(unsigned int m)
{
     	 dispbuf[2]= m/100 ;		// Get a hundred 
     dispbuf[1]= m/10%10      ;	// Get ten 
	   dispbuf[0]= m%10       ;	// Get bits  
}

void delay()
{
      unsigned char i;
   for(i=0;i<120;i++);	   // Time delay 1ms
}
/*AD transformation , It is read according to the sequence diagram , AD0809 The drive design of */
unsigned char ad_converse()	  //AD Conversion function 
{
      unsigned char temp;
   if(xuanzhe==1)
	 {
    addc=0;addb=1; adda=1;} // Select the channel 6 
   else  
	 {
    
	   addc=1 ; addb=0 ; adda=1;}// Select the channel 5
     start=  1     ;   
     delay();
     start=    0   ;	  //start The falling edge of the signal latches the channel , start-up AD
     if(!eoc)          ;   // wait for eoc  Lower 
     if(eoc)          ; // wait for eoc  When it gets higher, the conversion ends 
      temp=PC_ADDR;                // from PC Read the conversion result to temp
       return temp;                 // return AD Conversion result 
}

void main()
{
       unsigned int xianzhi_1;
	  unsigned char adresult;
    unsigned int voltage;
    CMD_ADDR=0x89   ; //8255 initialization , The way 0,A Mouth and B output ,C I want to input 
	  Timer0_Init(); 
	  buzz=0;
	  xianzhi_1=250;
    while(1)
	{
       
		
			
	
	 if(flag==1)	// Determine whether 50ms It's time to 
	       {
    flag=0;
		    adresult=ad_converse();	// Start once AD transformation , The results are stored in adresult
			    voltage=PC_ADDR*500.00/256;     // Digital quantity is converted into voltage value 
					 if(voltage>xianzhi_1)// range of waring is yourself setting,this is 2.50V
					 {
    baoj=~baoj;
					  buzz=1;}
					 else 
						 {
    
							 baoj=0;
					     buzz=0;
						 }
						 
		    disp   ay(voltage);  // Display the voltage value 
			}
	}	 
}