#include <reg51.h> //22．            電子琴
unsigned char code table[]={0x3f,0x06,0x5b,0x4f, 
                            0x66,0x6d,0x7d,0x07, 
                            0x7f,0x6f,0x77,0x7c, 
                            0x39,0x5e,0x79,0x71}; 
unsigned char temp; 
unsigned char key; 
unsigned char i,j; 
unsigned char STH0; 
unsigned char STL0; 
unsigned int code tab[]={64021,64103,64260,64400, 
                          64524,64580,64684,64777, 
                          64820,64898,64968,65030, 
                          65058,65110,65157,65178}; 
  
void main(void) 
{ 
  TMOD=0x01; 
  ET0=1; 
  EA=1; 
  
  while(1) 
    { 
      P3=0xff; 
      P3_4=0; 
      temp=P3; 
      temp=temp & 0x0f; 
      if (temp!=0x0f) 
        { 
          for(i=50;i>0;i--) 
          for(j=200;j>0;j--); 
          temp=P3; 
          temp=temp & 0x0f; 
          if (temp!=0x0f) 
            { 
              temp=P3; 
              temp=temp & 0x0f;              
              switch(temp) 
                { 
                  case 0x0e: 
                    key=0; 
                    break; 
                  case 0x0d: 
                    key=1; 
                    break; 
                  case 0x0b: 
                    key=2; 
                    break; 
                  case 0x07: 
                    key=3; 
                    break; 
                } 
              temp=P3; 
              P1_0=~P1_0; 
              P0=table[key]; 
              STH0=tab[key]/256; 
              STL0=tab[key]%256; 
              TR0=1; 
              temp=temp & 0x0f;              
              while(temp!=0x0f) 
                { 
                  temp=P3; 
                  temp=temp & 0x0f;              
                } 
              TR0=0; 
            } 
        } 
  
      P3=0xff; 
      P3_5=0; 
      temp=P3; 
      temp=temp & 0x0f; 
      if (temp!=0x0f) 
        { 
          for(i=50;i>0;i--) 
          for(j=200;j>0;j--); 
          temp=P3; 
          temp=temp & 0x0f; 
          if (temp!=0x0f) 
            { 
              temp=P3; 
              temp=temp & 0x0f;              
              switch(temp) 
                { 
                  case 0x0e: 
                    key=4; 
                    break; 
                  case 0x0d: 
                    key=5; 
                    break; 
                  case 0x0b: 
                    key=6; 
                    break; 
                  case 0x07: 
                    key=7; 
                    break; 
                } 
              temp=P3; 
              P1_0=~P1_0; 
              P0=table[key]; 
              STH0=tab[key]/256; 
              STL0=tab[key]%256; 
              TR0=1; 
              temp=temp & 0x0f;              
              while(temp!=0x0f) 
                { 
                  temp=P3; 
                  temp=temp & 0x0f;              
                } 
              TR0=0; 
            } 
        } 
  
      P3=0xff; 
      P3_6=0; 
      temp=P3; 
      temp=temp & 0x0f; 
      if (temp!=0x0f) 
        { 
          for(i=50;i>0;i--) 
          for(j=200;j>0;j--); 
          temp=P3; 
          temp=temp & 0x0f; 
          if (temp!=0x0f) 
            { 
              temp=P3; 
              temp=temp & 0x0f;              
              switch(temp) 
                { 
                  case 0x0e: 
                    key=8; 
                    break; 
                  case 0x0d: 
                    key=9; 
                    break; 
                  case 0x0b: 
                    key=10; 
                    break; 
                  case 0x07: 
                    key=11; 
                    break; 
                } 
              temp=P3; 
              P1_0=~P1_0; 
              P0=table[key]; 
              STH0=tab[key]/256; 
              STL0=tab[key]%256; 
              TR0=1; 
              temp=temp & 0x0f;              
              while(temp!=0x0f) 
                { 
                  temp=P3; 
                  temp=temp & 0x0f;              
                } 
              TR0=0; 
            } 
        } 
  
      P3=0xff; 
      P3_7=0; 
      temp=P3; 
      temp=temp & 0x0f; 
      if (temp!=0x0f) 
        { 
          for(i=50;i>0;i--) 
          for(j=200;j>0;j--); 
          temp=P3; 
          temp=temp & 0x0f; 
          if (temp!=0x0f) 
            { 
              temp=P3; 
              temp=temp & 0x0f;              
              switch(temp) 
                { 
                  case 0x0e: 
                    key=12; 
                    break; 
                  case 0x0d: 
                    key=13; 
                    break; 
                  case 0x0b: 
                    key=14; 
                    break; 
                  case 0x07: 
                    key=15; 
                    break; 
                } 
              temp=P3; 
              P1_0=~P1_0; 
              P0=table[key]; 
              STH0=tab[key]/256; 
              STL0=tab[key]%256; 
              TR0=1; 
              temp=temp & 0x0f;              
              while(temp!=0x0f) 
                { 
                  temp=P3; 
                  temp=temp & 0x0f;              
                } 
              TR0=0; 
            } 
        }      
    } 
} 
  
void t0(void) interrupt 1 using 0 
{ 
  TH0=STH0; 
  TL0=STL0; 
  P1_0=~P1_0; 
}