Hi,
If you want to use the IRQ pin, as an IRQ, set the IRQPE bit om the IRQSC register to 1.
If you have set the IRQPE pin, you can select if you want to have falling or rising edge triggering the IRQ interrupt, by clearing setting IRQEDG bit.
The IRQPE is cleared as default, so initially the IRQ interrupt is disabled.
If you don't want to use the IRQ pin at all, I would connect a 10 kOhm pullup resistor and a 0.1 uF capacitor to the IRQ pin, and not write anything to the IRQSC register.
Did that answer your question?
Regards,
Ake