Detect one shot signal from Nios II

You are more than likely missing the pulsed signal. I was running into the same issue. I was providing the nios with a 1cc pulsed signal as an interrupt. The nios was on the same clock domain, but it was still missing it.

The solution was to use an active high level interrupt. This interrupt remains high until the nios acknowledges it, then the nios goes out and clears it. This was accomplished by writing to a "clear" register that I implemented in the interrupt generating component.