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Nios response IRQ custom block



I have problems to detect an IRQ with Nios from a custom VHDL block.

Really, I don't have problems to detect it, but the first time that this IRQ is generated and detected, the Nios keeps the signal at high level for seconds (when in my block I put it in high level for 2 us).

Can anybody help me in undestand why the Nios reacts as commented?

After the first time, when an irq is generated it is detected immediately by the Nios and the isr code executed immediately. So this behavior only appears the first time that the irq is detected, why? Is there any solution to solve it? To "solve" it for the moment, I have connected the irq pulse to an PIO block and connect it as an interrupt to the VIC. But it is probably not the best solution.

I have tested that the vhdl code works as expected, monitoring the signals without turn on the Nios, and the signals times and behavior is the expected.

Thank you so much for your support.

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It could be your Nios is boooting from flash.

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