是用中断,计时函数micros的原型如下,函数原型要用到interrupt.h这个头文件
unsigned long micros() {
unsigned long m;
uint8_t oldSREG = SREG, t;
cli();
m = timer0_overflow_count;
#if defined(TCNT0)
t = TCNT0;
#elif defined(TCNT0L)
t = TCNT0L;
#else
#error TIMER 0 not defined
#endif
#ifdef TIFR0
if ((TIFR0 & _BV(TOV0)) && (t < 255))
m++;
#else
if ((TIFR & _BV(TOV0)) && (t < 255))
m++;
#endif
SREG = oldSREG;
return ((m << 8) + t) * (64 / (F_CPU/1000000L));
}