这个程序的原理怎么看不明白？蜂鸣器为什么会响？

2019-07-15 18:29发布

就是这个
#include<reg51.h>

#define uchar unsigned char

uchar a0=16,b0=16,c0=16,d0=16,e0=16,f0=16,wei,temp,key,i,j,k;
sbit dula=P2^6;
sbit wela=P2^7;
sbit beep=P2^3;

unsigned char code table[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,
                     0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71,0x00};

void delay(uchar i)
{
for(j=i;j>0;j--)
for(k=125;k>0;k--);
}
void display(uchar a,uchar b,uchar c,uchar d,uchar e,uchar f)
{
dula=0;
P0=table[a];
dula=1;
dula=0;

wela=0;
P0=0xfe;
wela=1;
wela=0;
delay(5);

P0=table[b];
dula=1;
dula=0;

P0=0xfd;
wela=1;
wela=0;
delay(5);

P0=table[c];
dula=1;
dula=0;

P0=0xfb;
wela=1;
wela=0;
delay(5);

P0=table[d];
dula=1;
dula=0;

P0=0xf7;
wela=1;
wela=0;
delay(5);

P0=table[e];
dula=1;
dula=0;

P0=0xef;
wela=1;
wela=0;
delay(5);

P0=table[f];
dula=1;
dula=0;

P0=0xdf;
wela=1;
wela=0;
delay(5);
}

void keyscan()
{
  {
P3=0xfe;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
   delay(10);
   if(temp!=0xf0)
   {
      temp=P3;
      switch(temp)
      {
      case 0xee:
            key=0;
   wei++;
            break;

      case 0xde:
            key=1;
   wei++;
            break;

      case 0xbe:
            key=2;
   wei++;
            break;

      case 0x7e:
            key=3;
   wei++;
            break;
      }
      while(temp!=0xf0)
      {
         temp=P3;
         temp=temp&0xf0;
         beep=0;
      }
      beep=1;
   }
}
P3=0xfd;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
   delay(10);
   if(temp!=0xf0)
   {
      temp=P3;
      switch(temp)
      {
      case 0xed:
            key=4;
   wei++;
            break;

      case 0xdd:
            key=5;
   wei++;
            break;

      case 0xbd:
            key=6;
   wei++;
            break;

      case 0x7d:
            key=7;
   wei++;
            break;
      }
      while(temp!=0xf0)
      {
         temp=P3;
         temp=temp&0xf0;
         beep=0;
      }
      beep=1;
   }
   }
P3=0xfb;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
   delay(10);
   if(temp!=0xf0)
   {
      temp=P3;
      switch(temp)
      {
      case 0xeb:
            key=8;
   wei++;
            break;

      case 0xdb:
            key=9;
   wei++;
            break;

      case 0xbb:
            key=10;
   wei++;
            break;

      case 0x7b:
            key=11;
   wei++;
            break;
      }
      while(temp!=0xf0)
      {
         temp=P3;
         temp=temp&0xf0;
         beep=0;
      }
      beep=1;
   }
   }
      P3=0xf7;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
   delay(10);
   if(temp!=0xf0)
   {
      temp=P3;
      switch(temp)
      {
      case 0xe7:
            key=12;
   wei++;
            break;

      case 0xd7:
            key=13;
   wei++;
            break;

      case 0xb7:
            key=14;
   wei++;
            break;

      case 0x77:
            key=15;
   wei++;
            break;
      }
      while(temp!=0xf0)
      {
         temp=P3;
         temp=temp&0xf0;
         beep=0;
      }
      beep=1;
   }
}
}
}
  void main()
  {
    while(1)
{
    keyscan();
if(key!=20)
{
switch(wei)
{
case 1: a0=key;
b0=16;
c0=16;
d0=16;
e0=16;
f0=16;
break;
case 2: b0=key;
c0=16;
d0=16;
e0=16;
f0=16;
break;
case 3: c0=key;
d0=16;
e0=16;
f0=16;
break;
case 4: d0=key;
e0=16;
f0=16;
break;
case 5: e0=key;
f0=16;
break;
case 6: f0=key;
wei=0;
break;
}
key=20;
}
display(a0,b0,c0,d0,e0,f0);
}
}

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