定时器1基础实验：让PB口上接的LED循环闪亮

#include
unsigned char n=0;
void port_init(void) //端口初始化函数
{
 DDRB  = 0xFF;   //B口定义为输出
}

void timer1_init(void)    //定时器1初始化：0.5秒定时，预分频256
{
 TCCR1B = 0x00;      //stop
 TCNT1H = 0xF8;      //setup
 TCNT1L = 0x5F;
 TCCR1A = 0x00;
 TCCR1B = 0x04;       //start Timer
}

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

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

#pragma interrupt_handler timer1_ovf_isr:9
void timer1_ovf_isr(void) //定时中断入口
{
 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;
 }
}