S-DSP KeyOn/KeyOff read

This is an archive of a topic from NESdev BBS, taken in mid-October 2019 before a server upgrade.
View original topic
S-DSP KeyOn/KeyOff read
by on (#48910)
I'd like to know what reads back on KeyOn and KeyOff registers of the sound DSP. I don't see it really doccumented. Anyone have a clue ?

What about reading $7c (voice end). Are the bit here set only when a sample ends, or are they also set when a sample loops ?

Also reading $x8 reads back enveloppe value. But reding $x9 is more obscure. Supposely, it reads the wave being played on the Xth channel, but aren't samples 16-bit ? Are the read affected by noise, enveloppe, echo and volume ?

Another one I'd be curious : Is it possible to abuse the echo buffer to play additional non-BRR samples ? Has anyone ever tried such a thing before ?