8255.c

8255实现并行口的扩展

unsigned char xdata  porta _at_ 0x8fff;
unsigned char xdata portb _at_ 0x9fff;
unsigned char xdata portc _at_ 0xafff;
unsigned char xdata cadrr _at_ 0xbfff;
unsigned char xdata *i _at_ 0x0060;
unsigned char xdata *b _at_ 0x0070;	//必须为字符型且作用域必须相同
 //m=0xf7;
#include<AT89X51.h>
//#include<stdio.h>
#include<INTRINS.H>
//unsigned char  led[9]={ 0xff , 0xf7,0xfb,0xfd,0xfe,0xef,0xdf,0xbf,0x7f};
void main (void)
{

   i = &cadrr;
 *i=0x80;
 b=&portc;
 //unsigned char m;
 
while (1)		   
{
unsigned char n;
unsigned int a;
 unsigned char n1=0;
unsigned char m=0x7f;

 for ( n=0;n<8;n++)
 {//*b=led[n];
 n1++;
 //if(n1<4)
  *b=m;
 for (a=0;a<60000;a++) ;
 //m>>=1;
  
  /*
  else
  {
  m=0xef;
  *b=m;
  for (a=0;a<60000;a++);
  m>>=1;
  }	
   */
  m=_cror_ (m,1); 	//必须赋给别的变量
 }
}
}