#define PIO_INTERRUPT_LEVEL    6
int count_interrupt;
__ramfunc void pio_c_irq_handler ( void )
{
int dummy;
count_interrupt++;
    dummy =AT91C_BASE_PIOA->PIO_ISR;
    //* suppress the compilation warning
    dummy =dummy;

}


int main( void )
//* Begin
{
    unsigned int   loop_count;
    AT91PS_AIC     pAic;
    //* Load System pAic Base address
        pAic = AT91C_BASE_AIC;

    //* Enable User Reset and set its minimal assertion to 960 us
    AT91C_BASE_RSTC->RSTC_RMR = AT91C_RSTC_URSTEN | (0x4<<8) | (unsigned int)(0xA5<<24);

        // First, enable the clock of the PIOB
        AT91F_PMC_EnablePeriphClock ( AT91C_BASE_PMC, 1 << AT91C_ID_PIOA );
        AT91F_PIOA_CfgPMC();
    //* open external PIO interrupt
        //* define switch SW3 at PIO input for interrupt IRQ loop
    AT91F_PIO_CfgInput(AT91C_BASE_PIOA, SW3_MASK | SW4_MASK);

    AT91F_AIC_ConfigureIt ( pAic, AT91C_ID_PIOA, PIO_INTERRUPT_LEVEL,AT91C_AIC_SRCTYPE_INT_POSITIVE_EDGE, pio_c_irq_handler);
    AT91F_PIO_InterruptEnable(AT91C_BASE_PIOA,SW4_MASK);
    //* set the interrupt by software
    AT91F_AIC_EnableIt (pAic, AT91C_ID_PIOA);

for (;;)
    {

    }

//* End
}

#pragma vector = 0x18
__irq __arm void IRQ_Switch()
{
    void (*Handler)() = (void(*)())AT91C_BASE_AIC->AIC_IVR;
    Handler();
    AT91C_BASE_AIC->AIC_EOICR = 0;                    // Reset AIC logic
}