Tutorial for C/C++ programming

all right I answer as far as I can.

- set_pio_irq_mask

I don't know what is this function.

but I know what does it do.

this function sets value on the address of PIO.

http://www.altera.com/literature/ug/ug_embedded_ip.pdf

(page 10-7)

it masks which IO should / should not be enable for interrupt.

for example 0x01 is set, which means bit0 of PIO is enable as interrupt pin.

- set_pio_edge_cap

this function set if the interrupt should be LEVEL interrupt or edge captured interrupt.

if it set 0 which means this interrupt is LEVLE interrupt ( I'm not sure if it is opposed).

- alt_irq_register

I'm sure you can find document.

http://www.altera.com/literature/hb/nios2/n2sw_nii52010.pdf

(on page 14-40)

register the interrupt on your system. and specify function which is called when the interrupt is occurred.

is that answer what you want?