[Coco] Color Computer cart addresses / CoCo PSG

[S Klammer]

Would it be a thought to implement a sharing mechanism?

A fixed set of bytes dedicated to new devices?  A byte or two to define the
cart and another to trigger it to act upon the following bytes?

Just a quick rambling, but we do appear to have limited options... even
though the likelyhood of any of these older carts being used (from the
existing list) would be slim(?)

Shain
On Dec 22, 2016 7:58 PM, "Zippster" <zippster278 at gmail.com> wrote:

>
> > On Dec 22, 2016, at 6:38 PM, RETRO Innovations <go4retro at go4retro.com>
> wrote:
> >
> > On 12/22/2016 2:00 PM, Zippster wrote:
> >> *SCS is active for $FF40-$FF5F if I understand correctly (R&W).  I
> think if I place
> >> the 5 addresses I need at the upper end of this I should be ok staying
> out of the way
> >> (and have the help of *SCS in doing so).
> > 5 addresses?  I thought the YM and the AY needed 16 addresses?  Are you
> doing indirect addressing?
>
> That should be 6 actually.  I have banking registers for the first 3, a
> control register on the 4th.
>
> The YM chip does have 16 registers internally, but communications with the
> chip uses 2 ports (addresses).
> You directly address the chips through these 2 ports.  One address to
> select the internal register, a subsequent
> read or write to the second address loads or reads out the register via
> the data bus.
>
> The AY chips are the same AFAIK.
>
> >>
> >> I had it at the lower end of the *SCS region, but it looked like the
> SDC modifies a reg
> >> on it’s initial search for other disk controllers (just a guess, I
> don’t know the procedure used).
> >> Not a big deal as it can easily be corrected in software once running,
> but if I can stay
> >> completely clear I’d rather.
> >>
> >> So I’m thinking $FF5B-$FF5F in conjunction with *SCS will be ok for
> decoding register
> >> access.  Easy to change if an issue crops up at least.  :)
> > You're OK in an MPI, but with a Y cable, FDC underdecodes all of *SCS,
> so you'll conflict.
>
> Good to know.
>
> >
> > Not saying you should move, just noting it so you're aware.
> >
> > Jim
> >
> >
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