Now that you've attached an interrupt

At this point, you've called either InterruptAttachEvent() or InterruptAttach().

Here's a code snippet that attaches an ISR to the hardware interrupt vector, which we've identified in our code sample by the constant HW_SERIAL_IRQ:

#include <sys/neutrino.h>

int interruptID;

const struct sigevent *
intHandler (void *arg, int id)

main (int argc, char **argv)
    interruptID = InterruptAttach (HW_SERIAL_IRQ, 
                                   sizeof (event), 
    if (interruptID == -1) {
        fprintf (stderr, "%s:  can't attach to IRQ %d\n",  
                 progname, HW_SERIAL_IRQ);
        perror (NULL);
        exit (EXIT_FAILURE);
    return (EXIT_SUCCESS);

This creates the association between the ISR (the routine called intHandler(); see below for details) and the hardware interrupt vector HW_SERIAL_IRQ.

At this point, if an interrupt occurs on that interrupt vector, our ISR will be dispatched. When we call InterruptAttach(), the kernel unmasks the interrupt source at the PIC level (unless it's already unmasked, which would be the case if multiple ISRs were sharing the same interrupt).