How to use interrupt?

I use the interrupt with the button pio like that:

# include <cyg/hal/io.h> // for IOWR and IORD

unsigned char ledpio;

cyg_interrupt int_pio;

cyg_handle_t int_pio_handle;

cyg_uint32 isr_pio( cyg_vector_t vector,

cyg_addrword_t data){

ledpio = ledpio|1; //

IOWR (LED_PIO_BASE , 0, ledpio);

cyg_interrupt_mask(vector);

cyg_interrupt_acknowledge(vector);

IOWR(BUTTON_PIO_BASE , 3, 0x00); // Reset the edgecapture register

ledpio = ledpio&~1; //

IOWR (LED_PIO_BASE , 0, ledpio);

return(CYG_ISR_HANDLED | CYG_ISR_CALL_DSR);

}

void dsr_pio( cyg_vector_t vector,

cyg_ucount32 count,

cyg_addrword_t data){

ledpio = ledpio|2; //

IOWR (LED_PIO_BASE , 0, ledpio);

cyg_interrupt_unmask(vector);

ledpio = ledpio&~2; //

IOWR (LED_PIO_BASE , 0, ledpio);

}

void cyg_user_start(void)

{

cyg_thread_create(..);

cyg_thread_resume(..);

cyg_interrupt_create(

BUTTON_PIO_IRQ, // in /include/cyg/hal/system.h

99,

55,

&isr_pio,

&dsr_pio,

&int_pio_handle,

&int_pio);

cyg_interrupt_attach(int_pio_handle);

cyg_interrupt_unmask( BUTTON_PIO_IRQ);

IOWR(BUTTON_PIO_BASE , 1, 0x00);// PIO in input

IOWR(BUTTON_PIO_BASE , 3, 0x00);// Reset the edgecapture register

IOWR(BUTTON_PIO_BASE , 2, 0x01);// unmask bit0 all other masked

}

I use the Altera demo board Cyclone EP1C20F400

with the pio core descriped in Chapter 7 of the Nios II Processor Reference Handbook