Re: YMZ284? Re: My Mockingboard Clone

[Michael J. Mahon <mjmahon@aol.com>]

Ralph <rwhyre@gmail.com> wrote:
> 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)

That should work fine. 

-michael  -  NadaNet 3.1:  http://home.comcast.net/~mjmahon