//參考程序A:WFREQUENCE.C 程序運(yùn)行前將S3的第2和第4撥碼開關(guān)撥到ON,用跳線將T0和P0.0短接，撥碼開關(guān)S1打開任一方波信號(hào)通道(2000KHZ,1000KHZ,500KHZ,250KHZ)；T0作為外部計(jì)數(shù)器，T1作為定時(shí)器，T1定時(shí)在1ms范圍內(nèi)察看計(jì)數(shù)器T0所計(jì)的數(shù)。計(jì)算出被測(cè)信號(hào)的頻率并顯示在LCD上.			
#include <c8051f020.h>                 // SFR declarations
#include <intrins.h>
unsigned long x;
unsigned char *lcdpoint;         /*指向 lcddata數(shù)組的指針*/
unsigned char lcd_data_count;    /*要顯示的數(shù)據(jù)個(gè)數(shù) */
unsigned char temp,data1;
unsigned char HMS[9]={"FREQUECE:"},YMD[10]={0x0,0x00,0X0,0X0,"Khz"};	
#define SYSCLK       11059200          /*外部晶振頻率*/
sbit	P31 = P3^1;
void SYSCLK_Init (void);   	    //系統(tǒng)時(shí)鐘初始化
void PORT_Init (void);		    //端口初始化
void Time01_Init(void);		    //定時(shí)器0/1初始化
void LCD_Init(void);
unsigned int Frequence;		    //外部脈沖數(shù)變量
unsigned int   FF1,FF2,FF3,FF4,FF;	
/*延時(shí)子程序*/
void sleep_ms(unsigned int count)
{
  unsigned char ii,jj;
  for(ii=0;ii<count;ii++)
    {
      for(jj=0;jj<250;jj++)
	  _nop_();			
    }	
}
void main (void) {
   WDTCN = 0xde;            /*無效看門狗*/
   WDTCN = 0xad;
   LCD_Init();
   SYSCLK_Init ();          /*初始化時(shí)鐘*/
   PORT_Init ();            /*初始化交叉開關(guān)和IO口*/
   Time01_Init();			/*初始化定時(shí)器0/1*/
   while (1) {
   	P31=0;
	sleep_ms(250);
	EA=1;					// 開總中斷
	TR1=1;					// 開定時(shí)器1
	TR0=1;					// 開定時(shí)器0
	   P6  = 0x0d;     
	   for(x=0;x<1000;x++);   //延時(shí)
	    lcdpoint=&HMS;
for(lcd_data_count=9;lcd_data_count>0;lcd_data_count--)//顯示"FREQUENCE:"
	    { 
		    data1=*lcdpoint;
	        P7 = data1; 		/*送字符數(shù)據(jù)*/
			P6 = 0x0c;
	        P6 = 0x0d;
	        lcdpoint++;
			for(x=0;x<100;x++);
		}                        //準(zhǔn)備送數(shù)據(jù)
	    //for(x=0;x<5000;x++);
	    lcdpoint=&YMD;
for(lcd_data_count=7;lcd_data_count>0;lcd_data_count--) //顯示"XXXXKhz"
	    { 
		    data1=*lcdpoint;
			if(data1<0x40)
			data1 += 0x30;		/*轉(zhuǎn)化成字符碼*/
		    P7 = data1; 		/*送字符數(shù)據(jù)*/
			P6 = 0x0c;
	        P6 = 0x0d;
	        lcdpoint++;
			for(x=0;x<100;x++);
		}
    }
}
void SYSCLK_Init (void)
{
   int i;                              /*延時(shí)計(jì)數(shù)器*/
   OSCXCN = 0x67;                      /*啟動(dòng)外部11.0592MHz晶振*/
   for (i=0; i < 255; i++) ;           /*等待外部晶體起振*/
   while ((OSCXCN & 0x80)==0x00) ;     /*查詢標(biāo)志位*/
   OSCICN = 0x08;  /*選擇外部晶體作為系統(tǒng)時(shí)鐘并使能時(shí)鐘丟失檢測(cè)*/                                              
}
void PORT_Init (void)
{
   XBR0    = 0x00;
   XBR1    = 0x02;						/*交叉開關(guān)使能T0*/
   XBR2    = 0x40;                      /*使能交叉開關(guān)和弱上拉*/
   P74OUT  = 0xf0;	                  	/*P6,P7為推挽輸出*/
}
void Time01_Init(void)
{
EA=0;			//關(guān)總中斷
TR0=0;			//關(guān)定時(shí)器0
TR1=0;			//關(guān)定時(shí)器1
IE=0x0A;		/*允許TF1/TF0標(biāo)志位（TCON.7/TCON.5）的中斷請(qǐng)求*/
				    /*定時(shí)器1/0發(fā)生溢出*/
TMOD=0x15; /*定時(shí)器1是16位定時(shí)器方式，定時(shí)器0是16為計(jì)數(shù)器（T0腳)方式*/
IP=0x08;		/*定時(shí)器1是高優(yōu)先級(jí)中斷*/
CKCON=0x10;		/*定時(shí)器1的時(shí)基是系統(tǒng)時(shí)鐘*/
TH1=(-SYSCLK/1000)>>8;	/*定時(shí)1ms,定時(shí)器1使用系統(tǒng)時(shí)鐘*/
TL1=-SYSCLK/1000;
}
void TIMER1_ISR (void) interrupt 3 using 1
{        P31=1;          /*關(guān)閉被測(cè)信號(hào)源*/
		TF1=0;		 	 /*清中斷標(biāo)志*/
		TR1=0;			 /*關(guān)定時(shí)器1*/
		Frequence=TH0*0x100+TL0;/*外部脈沖數(shù) 單位 KHz*/
		TR0=0;	
		FF4=Frequence/1000;     /*將頻率數(shù)據(jù)轉(zhuǎn)化單字節(jié)并存入數(shù)組中*/
		YMD[0]=FF4;
		FF=(Frequence-FF4*1000);
		FF3=FF/100;
		YMD[1]=FF3;
		FF=(FF-FF3*100);
		FF2=FF/10;
		YMD[2]=FF2;
		FF=(FF-FF2*10);
		FF1=FF;
		YMD[3]=FF1;
		TH0=0;	/*清定時(shí)器0到零*/
		TL0=0;
		TH1=(-SYSCLK/1000)>>8;			TL1=-SYSCLK/1000;
		TR1=1;							/*開定時(shí)器1*/
		TR0=1;							/*開定時(shí)器0*/
        P31=0;                          /*打開被測(cè)信號(hào)源*/
}
void LCD_Init(void)
{
   P6 = 0x09;
   for(x=0;x<50000;x++);
  P7 = 0x30;				/*一行顯示*/
  // P7 = 0x38;				/*兩行顯示*/
   P6 = 0x08;
   P6 = 0x09; 
   for(x=0;x<1000;x++);
   P7 = 0x0e;				/*顯示開，光標(biāo)顯示，光標(biāo)不閃爍*/
   P6 = 0x08;
   P6 = 0x09;
   for(x=0;x<1000;x++);
   P7= 0x06;				/*顯示增加，不平移*/
   P6 = 0x08;
   P6 = 0x09;
   for(x=0;x<5000;x++);
   P7 = 0x01;				/*清屏*/
   P6 = 0x08;
   P6 = 0x09; 
   for(x=0;x<5000;x++);
}