[Coco] Color Computer cart addresses / CoCo PSG

[S Klammer]

That's the ticket ;)

But between you, Ed and Darren... it looks like we'll run out of those 255
different devices pretty quick! :)

Thanks for all of the new Coco stuff and a Merry Christmas!

(2017 looks to become an expensive year in terms of possible acquisitions)

Shain
On Dec 23, 2016 1:20 AM, "RETRO Innovations" <go4retro at go4retro.com> wrote:

> On 12/22/2016 9:56 PM, S Klammer wrote:
>
>> 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?
>>
> The mechanism I defined requires just 1 fixed byte, $ff80, and is
> write-only, so won't bother Coco3 units.
> To set a config option, you write $55/$aa/<devid>/<cmd>/<data> to $ff80.
>
> To set a base address, for example, on the CocoFLASH main registers, to
> $ff60:
> $55
> $aa
> $21
> $01 (set base address)
> $60 ($ff60)
>
> To set the base address, for example, on the CocoFLASH implementation of
> the ORCH90 to $ff70:
> $55
> $aa
> $11 (1= TANDY, 1= ORCH90)
> $01 (set base address)
> $70 ($ff70)
>
> You can define more than 1 command if desired, and the devid can be used
> to represent up to 255 different devices.  You an even handle more than 1
> of a unit in an MPI:
>
> $55
> $aa
> <devid>
> $01 (set base address)
> $40 ($ff40, in SCS space, then you can individually reference up to 4
> units, all at the same address)
>
> CocoNIC is devid $22, while the ROM in it follows the CocoFLASH layout and
> responds to devid=$21
>
> It's a bit much for discrete logic, but just a few macrocells in a CPLD to
> implement (uses a state machine and a single register to hold the base
> address of the unit).  Confirmed working on an MPI, and seems pretty
> extensible.
>
> Jim
>
>
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