计数用来实现频率计

//频率计
#include<avr/io.h>
#include<avr/interrupt.h>
#include<util/delay.h>
#include"my12864bing.h"
#define BIT(x) (1<<x)
#define uchar unsigned char
#define uint unsigned int
#define NULL 0

volatile unsigned int FREQ=0 ,DISP_F=0;
volatile  unsigned int TIME_count=0;
void FREQ_to_display(void);
int main()
{
     Lcd_Init();

     PORTA=0XFF;
     DDRA=0XFF;             //LED IO口设为输出


EICRA = (1<<ISC31)|(1<<ISC30);
EIFR = 0;
EIMSK = (1<<INT3);



TCCR0 =(1<<CS02)|(1<<CS01)|(1<<CS00); //定时器0，1024分频
TCNT0 = 100 ;
TIMSK |= (1 << TOIE0);           //T/C0溢出中断允许