Timer

void TC0_Handler(void){
  // Some code to read temperature.
}

void Init_Timer(){
  int n = 0;

  // Select Timer_Clock1 - Clear all first 7 bits for: clock selected: TCLK1
  *TC0_CMR1 = ~(~*TC0_CMR1 | 0x0007);

  // ETRGEDG: External Trigger Edge Selection - Edges
  *TC0_CMR1 |= 3 << 8;

  // ABETRG: TIOA External Trigger Selection
  *TC0_CMR1 |= 1 << 10;

  // LDRA: RA Loading Selection
  *TC0_CMR1 |= 2 << 16;
  // LDRB: RB Loading Selection
  *TC0_CMR1 |= 1 << 18;

  //TC1XC1S: External Clock Signal 1 Selection -  Signal connected to XC1: TIOA0
  *TC0_BMR |= 2 << 2;

  // Enable pin B25
  *AT91C_PIOB_PER = 1 << 25;

  // Multiplex PB25 => TIOA0
  *AT91C_PIOB_ABMR = 1 << 25;
  *AT91C_PIOB_ABSR |= 1 << 25;

  NVIC_EnableIRQ(TC0_IRQn);

  // Enable interrupt
  // LDRBS: RB Loading
  *TC0_IER1 = 1 << 6;

  // Enable clock
  *TC0_CCR1 = 1 << 0;
  // Reset/Start clock
  *TC0_CCR1 = 1 << 2;
}