You can check it by reading data (Offset:0) or edgecapture (Offset:3) in the register of PIO Core.
Refer to data if you want to see the value of the input port of PIO, or refer to edgecapture if you want to see the result of edge detection as IRQ.
Please refer to the following document for register map etc.
Embedded Peripherals IP User Guide
( Search for Register Map for the PIO Core)
Please refer to the following document for how to implement interrupts using a Nios® II CPU.
(Reference) Nios® II Beginner's Guide - Implementing Interrupts
https://www.macnica.co.jp/business/semiconductor/articles/intel/95825/
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Category: Nios® II
Tools: Nios® II EDS
Devices: -