Level Detected Interrupts for PIO

[Altera_Forum]

If a PIO is configured to generate interrupts when a "Level" is detected, how should I handle this in my interrupt service routine? I see the example for edge detected inputs in "count binary", but I am not sure what to do for level detected inputs. For a level detected enabled input, does the interrupt remain active the entire time the input is high?

[Altera_Forum]

smfelsher, 

 By defining the interrupt as level sensitive, you are stating that the following behavior is what you want:  irq = |(irq_mask & pio_data)  This means that if any of the bits in pio_data and the corresponding bit in irq_mask are high, the irq will be generated.  If you're looking for something that detects events on each and every bit, I think you'd be happier with edge_capture. The edge_capture register will also hold event values until it is cleared (by writing to it).  I hope this helps.  Best Regards,  slacker  P.S.: You could use your IRQ_MASK settings to define different sorts of interrupt events. It all depends upon what sort of hardware you're trying to interface with...  P.S.: Even if you're not an HDL expert, looking at what happens in the verilog or VHDL that's generated with any of the various PIOs is a useful exercise to understand what the hardware is doing.

[Altera_Forum]

With the respect to edge cpature inputs, it's clear how the IRQ is handled and cleared. But, when a PIO input is configured to generate an IRQ on a LEVEL, when/how does the IRQ assertion clear? For example, assume a PIO is configured to generate an IRQ when a level is detected. In software, the PIO interrupt handler simply reads the data register, stores it into a variable (i.e. pio_in_data), and exits. The "main" body of the program simply runs a loop printing the contents of pio_in_data when new data arrives. With this program running on a Nios dev. board with the PIO configured for the push-buttons, what if the user were to press and hold one of the buttons. The button input would remain at a "level" for a long period. The IRQ would assert, my interrupt handler would execute and exit. Is the IRQ still asserted? Would the program re-enter my interrupt handler since the input was still detected at a high "level"? 

 I agree that the edge capture would be the better solution for my example, but I would like to better understand the usefulness of a level detected configuration. I guess I'll have to try programming my example situation.  Thanks for your time.