YMZ284? Re: My Mockingboard Clone

[Ralph <rwhyre@gmail.com>]

On Aug 3, 4:59 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
> On 8/3/2010 12:30 PM, Linards Ticmanis wrote:
> > On 08/03/2010 03:00 PM, Polymorph wrote:
>
> >> I just completed implementing my most challenging hardware project to
> >> date - a Mockingboard clone!
>
> > Also, if you do your own programming for the card and don't just want to
> > use it with existing games, it makes sense to connect PB6 to PB7 on each
> > of the VIAs (kudos to Michael Mahon, IIRC, for that idea).
>
> It's also worth noting that a Mockingboard has two mostly unused ports
> on the two 6522s (six bits on each), and four completely unused ports
> on the AY-3-8910s (16 bits on each).  The AY ports are much less
> versatile than the 6522's and an extra bit fiddle away (accessed through
> the 6522s) but they are there, and completely unused.  It could have
> supported a pretty flashy LED display!  ;-)
>
> -michael

Since the AY-3-8910s ports are unused, could you replace them with a
variant
of the 8910 without the extra I/O pins?  I'm thinking of using a 6522
and the
YMZ284D chip, which is supposed to have the same registers as the
YM2149, but
without the I/O pins.  It has the 8-bit parallel input, but no digital
I/O
ports (just the three sound channels merged into a single Audio output
pin)