Probleme mit Interrupt AT91SAM7X

//main.c

#include <AT91SAM7X256.H>

#include "AT91SAM7X-EK.h"

#define INTTAST = AT91B_SW1;

void ex_int_handler (void){

  volatile unsigned int dummy;

  dummy = AT91C_BASE_PIOA->PIO_ISR;

  AT91C_BASE_AIC->AIC_EOICR=AT91C_BASE_TC0->TC_SR;

  AT91C_BASE_AIC->AIC_ICCR=(1<<AT91C_ID_TC0);

  *AT91C_AIC_EOICR=0;

  AT91C_BASE_PIOB->PIO_CODR=AT91B_LED1;// LED1 hier zum Int.-Test anmachen

  AT91C_BASE_AIC->AIC_EOICR = 0;

}

int main(void){

  int io_status;

  // Enable the Clock of the PIO

  AT91C_BASE_PMC->PMC_PCER  = 1 << AT91C_ID_PIOA;

  AT91C_BASE_PMC->PMC_PCER  = 1 << AT91C_ID_PIOB;

  AT91C_BASE_PMC->PMC_PCER  = 1 << AT91C_ID_SYS;

  // Configure the PIO Lines corresponding to LED1..LED4 as Outputs

  AT91C_BASE_PIOB->PIO_PER  = AT91B_LED_MASK;

  AT91C_BASE_PIOB->PIO_OER  = AT91B_LED_MASK;

  // Clear the LED's. On the Board we must apply a "1" to turn off LEDs

  AT91C_BASE_PIOB->PIO_SODR = AT91B_LED_MASK;

  //Init Interrupt

  AT91C_BASE_PIOA->PIO_PER=AT91B_SW1;

  AT91C_BASE_PIOA->PIO_ODR =AT91B_SW1;

  AT91C_BASE_PIOA->PIO_CODR=AT91B_SW1;

  AT91C_BASE_PIOA->PIO_PPUER=AT91B_SW1;

  AT91C_BASE_PIOA->PIO_ASR=AT91B_SW1;

  AT91C_BASE_PIOA->PIO_OWDR=AT91B_SW1; 

  AT91C_BASE_AIC->AIC_SMR[AT91C_ID_PIOA]=AT91C_AIC_SRCTYPE_INT_POSITIVE_EDGE | 0; 

  AT91C_BASE_AIC->AIC_SVR[AT91C_ID_PIOA]=(unsigned int)ex_int_handler; 

  AT91C_BASE_PIOA->PIO_IFER=AT91B_SW1; 

  io_status = AT91C_BASE_PIOA->PIO_ISR; 

  AT91C_BASE_AIC->AIC_IECR=(1 << AT91C_ID_PIOA);

  AT91C_BASE_AIC->AIC_ISCR=(1 << AT91C_ID_PIOA); //Test

  AT91C_BASE_AIC->AIC_ICCR=0;

  AT91C_BASE_PIOA->PIO_IER=AT91B_SW1;

  for(;;){

    if ((AT91C_BASE_PIOA->PIO_PDSR & AT91B_SW3) == 0) {       /* Check if SW3 is pressed */

      AT91C_BASE_PIOB->PIO_CODR = AT91B_LED2;      /* Turn On LED2 */

    }

    if ((AT91C_BASE_PIOA->PIO_PDSR & AT91B_SW4) == 0) {             /* Check if SW4 is pressed */

      AT91C_BASE_PIOB->PIO_SODR = AT91B_LED2;      /* Turn Off LED2 */

    }  

  }

}