key.c

At89s52单片机与max197的AD程序

#include "main.h"
#include "reg52.h"


  
  void Delay()
  {
    unsigned char i;
    for(i=200;i>0;i--)
    {}
  }

  
unsigned char Key_Scan()
 {
    unsigned char S_ccode,R_ecode;
    P3=0xf0;
    if((P3&0xf0)!=0xf0)
      {
        Delay();
        if((P3&0xf0)!=0xf0)
          {
            S_ccode=0xfe;
            while((S_ccode&0x10)!=0)
        	   {
                  P3=S_ccode;
                  if((P3&0xf0)!=0xf0)
            	     {
                       R_ecode=(P3&0xf0)|0x0f;
                       return((~S_ccode)+(~R_ecode));
            		  }
            	 else
                   S_ccode=(S_ccode<<1)|0x01;
        		}
           }
       }
    return(0);
 }