中断函数是如何被识别的

/* 1 second interval when assuming 1 MHz clock frequency and 1024x prescaling */

#define TOP (1000000/1024) 



/**************************************************************************//**

 * [url=home.php?mod=space&uid=247401]@brief[/url] Initialize TIMER0 in Up/Down Count mode and to give interrupts when 

 * turning from counting up to down (overflow) and from down to up (underflow)

 *****************************************************************************/

void initTimer()

{  

  TIMER_Init_TypeDef initValues = TIMER_INIT_DEFAULT;

  

  /* Enable clock for TIMER0 */

  CMU_ClockEnable(cmuClock_TIMER0, true);

  

  /* Enable underflow and overflow interrupt for TIMER0*/

  TIMER_IntEnable(TIMER0, TIMER_IF_OF);

  TIMER_IntEnable(TIMER0, TIMER_IF_UF);

  

  /* Enable TIMER0 interrupt vector in NVIC */

  NVIC_EnableIRQ(TIMER0_IRQn);

  

  /* Set TIMER0 Top value */

  TIMER_TopSet(TIMER0, TOP);

  

  /* Initialize TIMER0 in Up/Down mode with 1024x prescaling */

  initValues.prescale = timerPrescale1024;

  initValues.mode     = timerModeUpDown;

  TIMER_Init(TIMER0, &initValues);

  

  /* Start TIMER0 */

  TIMER0->CMD = TIMER_CMD_START;

}





/**************************************************************************//**

 * @brief TIMER0 Interrupt Handler. Writes status to LCD display

 *****************************************************************************/

void TIMER0_IRQHandler(void)

{ 



  /* Store the interrupt flags before clearing */

  uint16_t intFlags = TIMER_IntGet(TIMER0);

  

  /* Clear the interrupt flags. Only clear the flags that were stored in */

  /* intFlags in case other flags have been set since then */

  TIMER_IntClear(TIMER0, intFlags);



  /* Overflow interrupt occured */

  if(intFlags & TIMER_IF_OF)

  {

    SegmentLCD_Write("OVER");

  }

  

  /* Underflow interrupt occured */

  if(intFlags & TIMER_IF_UF)

  {

    SegmentLCD_Write("UNDER");

  }

}





/**************************************************************************//**

 * @brief Main function

 *****************************************************************************/

int main(void)

{  

  /* Chip revision alignment and errata fixes */

  CHIP_Init();

  

  /* Set system frequency to 1 MHz */

  CMU_HFRCOBandSet(cmuHFRCOBand_1MHz);

  

  /* Initialize LCD */

  SegmentLCD_Init(false); 



  /* Initialize TIMER0 */

  initTimer();

  

  /* Go to EM1 when not servicing interrupts */

  while(1)

  {

    EMU_EnterEM1();

  }

}