Interrupts

I would like to do the next thing.

If I use P9.1 like as general input I'd like to do some operations when this input is set. How can I do it?

I have try that:

void hello(void) {
printf("Hello, willow\n");
}


void main(void)
{
MAIN_vInit();

while (1)
{
if (P9_P0) {
hello();
}
}
}


With this example I'm wrong because hello repeats so many times until P9.0 is reset. I don't want do that, I would like to do this only one time and I'm thinking to do hello like an interrupt but I don't know how.