Here's another bit of weirdness that appears to only happen on real hardware, not any emulators. When some code is using DPCM for sample playback an extra pulse is generated on the controller read line. That messes up the controller reading routine by shifting the output. When the last read is done all the buttons have already been sent so it gets a false trigger on the right button. The same thing seems to be happening on the Yobo and FC Twin clones, haven't tested NEX or RetroDuo yet.
The pulse is about 3x as wide as the normal read ones, and appears to only happen shortly after the write to $4016. It doesn't always happen and not always the same period after the write. Logic analyzer capture below. The added pulse is between C and D.
Has anyone else seen this before, or can write some good test apps? Audio is one part I don't really understand.
The pulse is about 3x as wide as the normal read ones, and appears to only happen shortly after the write to $4016. It doesn't always happen and not always the same period after the write. Logic analyzer capture below. The added pulse is between C and D.
Has anyone else seen this before, or can write some good test apps? Audio is one part I don't really understand.