#include

#include
unsigned char n=0;
void port_init(void) //端口初始化函數(shù)
{
DDRB = 0xFF; //B口定義為輸出
}

void timer1_init(void) //定時器1初始化：0.5秒定時，預分頻256
{
TCCR1B = 0x00; //stop
TCNT1H = 0xF8; //setup
TCNT1L = 0x5F;
TCCR1A = 0x00;
TCCR1B = 0x04; //start Timer
}

void main(void)
{
port_init();//初始化輸出端口
CLI(); //disable all interrupts

MCUCR = 0x00;
GICR = 0x00;
TIMSK = 0x05; //timer interrupt sources
SEI(); //re-enable interrupts
//all peripherals are now initialised
timer1_init();//定時器1初始化
while(1)//循環(huán)
{
;
}
}

#pragma interrupt_handler timer1_ovf_isr:9
void timer1_ovf_isr(void) //定時中斷入口
{
TCNT1H = 0xF8; //reload counter high value
TCNT1L = 0x5F; //reload counter low value
if(n>=1)
{
n=0;
PORTB=55;
}
else
{
PORTB=0xAA;
n=n+1;
}
}