Why my Nios® II design with PIO edge capture interrupt is not working?

This problem may be seen when users have chosen the incorrect setting for edge capturing, thus preventing interrupt from being triggered.

In the PIO(Parallel I/O) Intel® FPGA IP core, if the option “Enable individual bit setting/clearing” is turned off, writing any value to the edge capture register will clear all bits in the register. This is a default setting in Nios® II count binary template.

For example:

/* Reset the edge capture register. */

IOWR_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE, 0x0);

When the “Enable individual bit setting/clearing” option is turned on, writing a 1 to a particular bit in the register clears only that bit. For example:

/* Reset the edge capture register bit 0 and bit 1. */

IOWR_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE, 0x3); 

To work around this problem, choose the correct settings for the option “Enable individual bit setting/clearing.”

1. If enable bit-clearing for the edge capture register is turned off, writing any value to the edge capture register clears all bits in the register.
2. If enable bit-clearing for the edge capture register is turned on, writing a 1 to a particular bit in the register clears only that specific bit.

The PIO Intel® FPGA IP core user interface has been enhanced on description at the option “Enable individual bit setting/clearing,”  starting with the Intel® Quartus® Prime Pro/Standard Edition Software version 21.1