关于51 单片机的扫描问题、

#include<reg52.h>

#define uint unsigned int
#define uchar unsigned char

uchar code shumaguan[] = {0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};
uchar code table[] = {0xfe,0xfd,0xfb,0xf7,0xef,0xdf,0xbf,0x7f};

uchar key = 0;

void delays(int ms)
{
 int i;
 int j;
 for(i = 0;i<ms;i++)
  for(j = 0; j<124;j++);
}

void matrixkeyscan()
{
 uchar temp;

 P0 = 0xfe;
 temp = P0;
 temp = temp & 0xf0;
 if(temp != 0xf0)
 {
  delays(10);
  temp = P0;
  temp = temp & 0xf0;
  if(temp != 0xf0)
  {
   temp = P0;
   switch(temp)
   {
    case 0xee:
      key = 0;
     break;
    case 0xde:
     key = 1;
     break;
    case 0xbe:
     key = 2;
     break;
    case 0x7e:
     key = 3;
     break;
   } 
   while(temp != 0xf0)
   {
    temp = P0 ;
    temp = temp & 0xf0;
   }
   //display()  ;
  }
 }

 P0 = 0xfd;
 temp = P0;
 temp = temp & 0xf0;
 if(temp != 0xf0)
 {
  delays(10);
  temp = P0;
  temp = temp & 0xf0;
  if(temp != 0xf0)
  {
   temp = P0;
   switch(temp)
   {
    case 0xed:
      key = 4;
     break;
    case 0xdd:
     key = 5;
     break;
    case 0xbd:
     key = 6;
     break;
    case 0x7d:
     key = 7;
     break;
   } 
   while(temp != 0xf0)
   {
    temp = P0 ;
    temp = temp & 0xf0;
   }
   //display()  ;
  }
 }

 P0 = 0xfb;
 temp = P0;
 temp = temp & 0xf0;
 if(temp != 0xf0)
 {
  delays(10);
  temp = P0;
  temp = temp & 0xf0;
  if(temp != 0xf0)
  {
   temp = P0;
   switch(temp)
   {
    case 0xeb:
      key = 8;
     break;
    case 0xdb:
     key = 9;
     break;
    case 0xbb:
     key = 10;
     break;
    case 0x7b:
     key = 11;
     break;
   } 
   while(temp != 0xf0)
   {
    temp = P0 ;
    temp = temp & 0xf0;
   }
   //display()  ;
  }
 }

 P0 = 0xf7;
 temp = P0;
 temp = temp & 0xf0;
 if(temp != 0xf0)
 {
  delays(10);
  temp = P0;
  temp = temp & 0xf0;
  if(temp != 0xf0)
  {
   temp = P0;
   switch(temp)
   {
    case 0xe7:
      key = 12;
     break;
    case 0xd7:
     key = 13;
     break;
    case 0xb7:
     key = 14;
     break;
    case 0x77:
     key = 15;
     break;
   } 
   while(temp != 0xf0)
   {
    temp = P0 ;
    temp = temp & 0xf0;
   }
   //display()  ;
  }
 }
}

void main()
{
 while(1)
 {
  matrixkeyscan();
  P2 = table[0];
  P1 = shumaguan[key];
 }
}

今天，新讲的扫描，没有搞懂。 知道如何控制行，但，对于列的控制，很是不明白、。

期待，详细解释、