[Coco] CocoFlash Updates

[Gene Heskett]

On Sunday 18 September 2016 22:12:58 RETRO Innovations wrote:

> On 9/18/2016 6:03 AM, Gene Heskett wrote:
>  > Because most address decoding in the carts we have, are in 4 byte
>  > wide bits, no one has put anything at $FF7C-D-E because $FF7F is
>  > the multipack slot register. I have not verified the MPI's response
>  > to the C-D-E address myself, but if you only need one byte wide, I
>  > expect a little wrapping wire patch to your decoding could test it.
>
> I can test it no problem, but the Registered Port Address List shwos
> those addresses as being used:
>
> $ff7c: PBJ Buss slot select
> $ff7d:e: Speech/Sound pak
>
> I like the idea though.  $ff7e would be ideal.
>
>  > I have lamented for at least 25 years because someone hasn't made a
>  > one chip addin board for the coco itself, restricting the address
>  > space used by the PIA's to the 4 byte wide access they need, which
>  > would free up 7, 4 byte wide addresses from $FF04-FF1F, and 7 more
>  > 4 byte wide blocks from $FF24-FF3F. Thats 14 more 4 byte wide
>  > devices we could address in those two spaces. A single 74ALS138
>  > could manage that easily with one trace cut, two connections to the
>  > power rails, a bit of wirewrapping wire to put the 74ALS138 output
>  > into the CS logic of the 74LS138 in there now. Feed this '138 with
>  > A2 and A3 so that if either is true, the internal ls138 is
>  > disabled. This I repeat, would give us 14 more usable address
>  > blocks for a total of 21, as opposed to the 7 spaces we have now.
>
> Well, I think it is easier to do.  What would you like to put there? 
> I think I can disable them from the expansion port.
>
Thats what Darren said too.

> Give me an idea of what to put there, and I can whip up a prototype
> for you to test.
>
> Jim

Line up somebody with a stock machine to test with, mine has some hacks, 
and it is buried in concrete dust ATM from some demolition and repairs 
in our basement this summer.  About 13 grand worth, but we've had no 
water since.

Cheers, Gene Heskett
-- 
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