#include <mega16.h>
flash unsigned char led_7[11]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,0x00};
flash unsigned char position[4]={0xf7,0xfb,0xfd,0xfe};

unsigned char dis_buff[8];				// 顯示緩沖區(qū)，存放要顯示的8個(gè)字符的段碼值
unsigned char posit;
bit	freq_ok = 0;
unsigned char time2_new;
unsigned int freq;
unsigned long int freq_temp;          
unsigned char mode;

void display(void)				// 8位LED數(shù)碼管動(dòng)態(tài)掃描函數(shù)
{
	PORTC = 0xff;
	PORTA = led_7[dis_buff[posit]];
	if (posit==(mode+1)) 
	{
		PORTA = PORTA | 0x80; 
	}
	PORTC = position[posit]; 
	if (++posit >=4 ) 
		posit = 0;
 
}

// T/C0 比較匹配中斷服務(wù)，250個(gè)計(jì)數(shù)脈沖中斷一次
interrupt [TIM0_COMP] void timer0_comp_isr(void)
{
	time2_new = TCNT2;
	TCNT2 = 0;
	TIFR |= 0x02;	
	freq_temp = freq;
	freq = 0;
	freq_ok = 1;
}

// T/C2 比較匹配中斷服務(wù)，500us一次
interrupt [TIM2_COMP] void timer2_comp_isr(void)
{
	freq++;
	#asm("sei")		// 開(kāi)中斷，允許中斷嵌套，T/C0中斷可打斷該中斷服務(wù)
	display();
}

void freq_to_disbuff(void)		// 頻率值轉(zhuǎn)化為BCD碼送顯示緩沖區(qū)
{
	unsigned char i;
	PORTC=0xff;    
	for (i=3;i>=0&&i<4;i--)
	{     
		dis_buff[i] = freq_temp % 10;
		freq_temp = freq_temp / 10;
	} 
   	for (i=0;i<=3;i++)       // 高位零不顯示
	{
	    if (dis_buff[i] == 0)
	        dis_buff[i] = 10;
	    else
	        break;    
	} 
}

void main(void)
{
    unsigned char i;
    DDRA=0xFF;			// LED數(shù)碼管
	DDRC=0xff;
    DDRB.1=1;
	DDRB.2=1;    
    // T/C2初始化
    TCCR2=0x0A;			// 內(nèi)部時(shí)鐘，8分頻（4M/8=500KHz），CTC模式，
    TCNT2=0x00;			// 基時(shí)為2us
    OCR2=0xF9;			// OCR2 = 0xF9(249),(249+1)/500 = 0.5ms
	// T/C0初始化
    TCCR0=0x0E;			// 外部T0腳下降沿觸發(fā)計(jì)數(shù)，CTC模式
    TCNT0=0x00;
    OCR0=0xF9;			// OCR0 = 0xF9(249),(249 + 1) = 250

    TIMSK=0x82;			// 允許T/C2、T/C0比較匹配中斷

    for (i=0;i<=3;i++)
    	dis_buff[i] = 0; 
    	
    //設(shè)置模式
    //mode = 0; //(0- 99hz)
    //mode = 1; //(100-999hz)
    //mode = 2; //(1000 - 9999hz)
	//mode = 3; //(10,000 - 99,999hz)

    #asm("sei")			// 開(kāi)放全局中斷

    while (1)
    {
		if (freq_ok)
		{
			freq_temp = freq_temp * 250 + time2_new;	// 累計(jì)250個(gè)脈沖的時(shí)間間隔
			freq_temp = 12500000000/freq_temp;		// 換算成頻率,擴(kuò)大100倍，方便換算   			
			
			if(freq_temp >= 10000 && freq_temp < 100000)
			{
				freq_temp = freq_temp / 10;
				mode = 1; 
				PORTB=0x02;
			}
			else if(freq_temp >= 100000 && freq_temp < 1000000)
			{
				freq_temp = freq_temp / 100;
				mode = 2;
					PORTB=0x02;
			}
			else if(freq_temp>=1000000&&freq_temp<10000000)
			{
				freq_temp = freq_temp/100000;
				mode = 3;
					PORTB=0x04;
			}
			else
			{
				mode = 0; 
					PORTB=0x02;
			}
			freq_to_disbuff();						// 頻率值送顯示
			freq_ok = 0;
		}
    }
}