keyscan.c

The keyscan of MSC-51.In the programme you can neste use the keyscan and the code is so little.

#include<regx52.h>																																			#include <regx52.h>
unsigned char code table[]={0xc0,0xf9,0xa4,0xb0,
                            0x99,0x92,0x82,0xf8,
							0x80,0x90,0xa0,0x83,
							0xa7,0xa1,0x84,0x8e,
							0xff};
unsigned char key=16;
void keyscan()
{
  unsigned char temp,ridx=0xef,cidx=0xf7,aa,bb,cc;
  unsigned int i,j,i1,j1;
  for(i=0;i<4;i++)
   { 
   	P3=0xff;
	P3=(ridx<<i)|0x0f);
	temp=P3&0x0f;
	if(temp!=0x0f)
	{
	      for(i1=50;i1>0;i1--)
          for(j1=200;j1>0;j1--);
	      temp=P3&0x0f;
		  for(j=0;j<4;j++)
		  {
		  aa=temp|0xf0;
		  bb=cidx>>j;
		  cc=bb|0xf0;
			  if(aa==cc)
			  {
			    key=i*4+j;
			    break;
			  }	   
		  }
     }
    temp=P3;
	temp=temp & 0x0f;           
    while(temp!=0x0f)
    {
      temp=P3;
      temp=temp & 0x0f;              
    }

  }	 
}
void main()
{
   while(1)
   {
	   keyscan();
	   P2=table[key];
   }
}