月如镜 

 大家看看这个程序，可否解释一下
#include   <reg51.h>  
sbit PinScanKey1=P1^4;
sbit PinScanKey2=P1^5;
sbit PinScanKey3=P1^6;
sbit PinScanKey4=P0^4;
sbit PinScanKey5=P0^3;
#define TRUE 1
#define FALSE 0
#define DELAY_value 5
unsigned char a[8];
unsigned char bdata count;
sbit count0=count^0;
sbit count1=count^1;
sbit count2=count^2;
sbit p2_4=P2^4;
sbit p0_6=P0^6;
sbit p0_5=P0^5;
code unsigned char tb[31]={0xfc,0x60,0xda,0xf2,0x66,0xb6,0xbe,0xe0,0xfe,0xf6,0xee,0x3e,0x9c,0x7a,0x9e,0x8e,0x2e,0x1c,0x72,0x2a,0x3a,0xce,0x7c,0x00,0x10,0x80,0x02,0x82,0x1e,0x12,0x92};
/* ?0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,h,l,j,n,o,p,u,dark,low-,high-,mid-,high=,t,low=,三?``
*/

void delay(short i);
void keyinit(void);
unsigned char keyscan(void);

void coms() interrupt 1
 { TH0=0xf8;
   TL0=30;
   SBUF=tb[a[count]];
   p2_4=count0;
   p0_6=count1;
   p0_5=count2;
   while(TI) {
   TI=0; }
   if(count  <7)count++;
   else count=0;
  }

 void sinit(void)
 {SCON=0;
 TMOD=1;
 TH0=0x80;
 TL0=0x20;
 TR0=1;
 EA=1;
 ET0=1;
 TI=0;
 }

void keyinit(void)
{PinScanKey1=1;
 PinScanKey2=1;
 PinScanKey3=1;
 PinScanKey4=1;
 PinScanKey5=1;
}

void delay(short i)
{
   int k=0;
   k=i*DELAY_value;
   while(k--);
}

unsigned char keyscan()
{ if((PinScanKey1==FALSE)&&(PinScanKey2==FALSE))
         {delay(DELAY_value);
              if((PinScanKey1==FALSE)&&(PinScanKey2==FALSE))
                  {delay(DELAY_value);
                      if((PinScanKey1==FALSE)&&(PinScanKey2==FALSE))
                                return 6;}
         }
   if((PinScanKey1==FALSE)&&(PinScanKey3==FALSE))
         {delay(DELAY_value);
               if((PinScanKey1==FALSE)&&(PinScanKey3==FALSE))
                        {delay(DELAY_value);
                              if((PinScanKey1==FALSE)&&(PinScanKey3==FALSE))
                                   return 7;}
          }

   if(PinScanKey1==FALSE)
        {delay(DELAY_value);
           if(PinScanKey1==FALSE)
               {delay(DELAY_value);
                  if(PinScanKey1==FALSE)
                        return 1;}
         }

   if(PinScanKey2==FALSE)
          {delay(DELAY_value);
              if(PinScanKey2==FALSE)
                  {delay(DELAY_value);
                     if(PinScanKey2==FALSE)
                          return 2;}
           }

   if(PinScanKey3==FALSE)
        {delay(DELAY_value);
            if(PinScanKey3==FALSE)
                {delay(DELAY_value);
                   if(PinScanKey3==FALSE)
                       return 3;}
         }

  if(PinScanKey4==FALSE)
     {delay(DELAY_value);
           if(PinScanKey4==FALSE)
              {delay(DELAY_value);
                 if(PinScanKey4==FALSE)
                         return 4;}
     }

   if(PinScanKey5==FALSE)
       {delay(DELAY_value);
          if(PinScanKey5==FALSE)
              {delay(DELAY_value);
                  if(PinScanKey5==FALSE)
                      return 5;}
            }

   else return(a[7]);

   }
void main(void)
{
   sinit();
    do
   {keyinit();
   a[7]=keyscan();
   }while(1);
 }
这个程序是按键后，从数码管显示出来，比如按了1键，会显示1，按5会显示5，按1和2会显示6，按1和3会显示7，但是有一点，就是在按1到4这四个键时，没有问题，不按键时，数码管继续显示，但是5和6，7的话，松开手后立即就不显示了，请问谁能帮我解释一下。

发表时间:2003年9月3日22:39:54