#include <reg51.h>
unsigned char m; //m為頻率常數
unsigned char n=0; //n為節拍常數
unsigned char i=0;
sbit bell=P1^1;
unsigned char code music_tab[]={0x12,0x44,0x02,0x42,
	 0x42,0x01,0x41,0x12, //格式為: 頻率常數, 節拍常數, 頻率常數, 節拍常數,
	 0x21,0x31,0x44,0x44,
	 0x02,0x62,0x42,0x51,
	 0x61,0x82,0x01,0x81,
	 0x84,0x62,0x01,0x61,
	 0x42,0x01,0x61,0x82,
	 0x01,0x61,0x54,0x54,
	 0x04,0x94,0x84,0x54,
	 0x64,0x82,0x64,0x82,
	 0x42,0x01,0x51,0x64,
	 0x04,0x12,0x01,0x21,
	 0x42,0x42,0x62,0x01,
	 0x61,0x82,0x82,0x22,
	 0x01,0x21,0x54,0x02,
	 0x12,0x44,0x02,0x42,
	 0x64,0x02,0x62,0x84,
	 0x0C,0x42,0x01,0x61,
	 0x82,0x01,0x81,0x94,
	 0x84,0x62,0x01,0x41,
	 0x62,0x02,0x42,0x02,
	 0x14,0x44,0x62,0x01,
	 0x41,0x82,0x82,0x62,
	 0x02,0x42,0x02,0x14,
	 0x44,0x14,0x44,0x14,
	 0x44,0x44,0x04};

void time0(void) interrupt 1 using 1 //產生10MS精確定時
{TH0=55536/256;
 TL0=55536%256;
  n--;
}
void delayms(unsigned char a) //微秒延時程序
{
  while(--a);
}
void delay(void) //延遲程序
{
 int i,j;
 for(i=50;i--;i>0)
 for(j=10000;j--;j>0)
  ;
}
void main()
{
  
   TMOD=0x01;
   TH0=55536/256;
   TL0=55536%256;
   EA=1;
   ET0=1;
   TR0=0;
   while(1)
 {
  switch(music_tab[i])
 {
   case 0x00: i=0;delay();break; //曲終停頓一定時間
   case 0xff: i=i+1;delayms(100);break; //遇到休止符停頓一定時間100微秒,再取下一個頻率
   default:  m=music_tab[i++];n=music_tab[i++]; //取頻率到m,取節拍到n
   TR0=1;
    while(n!=0)
     {
      bell=!bell;
      delayms(4*m); //調整產生的頻率,可以通過在m前的值來修正音調的高低
      }
  TR0=0;
  }
 }
}