因为51单片机晶振的原因，测频的范围有限制，这时就需要外置74LS160分频器，进行分频。

本程序采用了定时器的方式2定时，8位自动重装计数器，精准定时。

单片机源程序：

#include

#include

#define Duan P2

#define Wei P1

sbit mr = P3^0;

unsigned char code smg_duan[] ={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};

unsigned char code smg_wei[] ={0xfe,0xfd,0xfb,0xf7,0xef,0xdf,0xbf,0x7f};

unsigned int Num;

long int pin;

long int count;

void delay_ms(int i)

{

int j;

for(i;i>0;i--)

for(j=100;j>0;j--);

}

void display(long int num)

{

long num1[8],i;

num1[7] = num/10000000;

num1[6] = (num/1000000)%10;

num1[5] = (num/100000)%10;

num1[4] = (num/10000)%10;

num1[3] = (num/1000)%10;

num1[2] = (num/100)%10;

num1[1] = (num/10)%10;

num1[0] = num%10;

for(i=0;i<8;i++){

Wei = smg_wei[i];

Duan = smg_duan[num1[i]];

delay_ms(1);

}

}

void main()

{

TMOD = 0x72;

TH0 = 0x06;

TL0 = 0x06;

TH1 = 0x00;

TL1 = 0x00;

ET1 = 1;

ET0 = 1;

EA = 1;

//PT1=1;

TCON = 0x50;

while(1)

{

display(pin);

}

}

void timer0() interrupt 1 //定时器

{

unsigned char a;

if(Num==3999)

{

TCON = 0x00;

EA=0;

Num = 0;

a=P0&0x0f; //分频器读数

pin = (256*count+TL1)*10+a; //溢出的次数*256+还未溢出的次数+分频器的计数

TH1 = 0x00;

TL1 = 0x00;

TL0 = 0x06;

TH0 = 0x06;

count = 0;

mr=0;

_nop_();

EA=1;

TCON = 0x50;

mr=1;

}

else Num++;

//display(pin);

}

void timer1() interrupt 3 //计数器

{

count++; 中断溢出的次数

}