> Yes, I confirm this ;-)
> The strange thing is that I was able to trace the Z80 activity and I confirm
> also that it's accessing (write and read) the mapped FM memory ... what do you
> think I should do to trace that further and see where the problem comes from ?
Check to see if it's sending anything meaningful or if it's stuck in some kind of loop. Since I don't know the details of your port, it's difficult for me to say where the problem could be. If Genesis Plus works on other systems, including its native DOS, then Charles' code is correct, and you'll have to find what you may have modified.
Consider: Are you using a different Z80 core? Have you rewritten the memory access handlers for the 68K and Z80? Have you modified the bus arbitration code (BUSREQ)?
> Note that in Genesis Plus, Sound Buffers are updated after each write and then
> completed at the end of the frame... I wonder also if that is really correct or
> could lead to such sound issue
I doubt it. You might want to periodically dump the sound buffer to make sure something intelligable is being written to it by the FM and PSG. If the method works in Genesis Plus on other systems, it should work for you, too.