5.c

来自「这是单片机C51典型应用设计代码」· C语言 代码 · 共 49 行

#include "reg51.h"
#define uchar unsigned char
#define uint unsigned int
void d1ms(void);
uchar kbscan(void); 

void main(void)
{
uchar key;
while(1)
{
key=kbscan();
d1ms();
}
}

void d1ms(void)
{
uchar i;
for(i=200;i>0;i--) {}
}

uchar kbscan(void)
{
uchar sccode,recode;
P1=0xf0;
if((P1&0xf0)!=0xf0)
{
  d1ms();
  if((P1&0xf0)!=0xf0)
   {
    sccode=0xfe;
    while((sccode&0x10)!=0)
    {
     P1=sccode;
     if((P1&0xf0)!=0xf0)
      {
       recode=(P1&0xf0)|0x0f;
       return((~sccode)+(~recode));
      }
     else sccode=(sccode<<1)|0x01;
    }
   }
  }
return(0);
}