[Coco] On John Linnville's Color Computer Game Master Cartridge Design

[RETRO Innovations]

On 8/2/2017 4:36 PM, John W. Linville wrote:
> On Wed, Aug 02, 2017 at 01:23:12PM -0500, RETRO Innovations wrote:
>
> Thanks for noticing! :-)
What I am trying to determine is what in the world they are doing int 
that IC.  I know there is a /8 on the incoming clock, which the '96 does 
not have, but even at 4 cycles, I can only assume they run some type of 
microcode inside on various clock states to configure the IC.  TI was 
known for such stuff.
> There is more than one way to do it, even with relatively simple
> logic. Checking schematics for a few of the old machines that used
> the device reveals a handful of viable options without resorting to
> on-board microcontrollers or programmable logic.
I used dedicated WE and CE lines, with READY feeding back, but your 
below approach obvious works as well.
>
> I've been meaning to do a blog write-up on the design. Maybe I should
> go ahead and do that soon...
I think it adds more color to the story.  I think some folks did a 
collective yawn on hooking up a small 16 pin IC with a CPU bus 
connection...  It's misleadingly complex.

I had hoped, though, to just ignore the READY line, but no joy.

BTW, has the cart been tested as Coco3 1.7MHz?  I ask because it looks 
like a !CE pulse smaller than 375nS will not trigger the operation, and 
the E high period at 1.79MHz is 279nS, I think (if my late night math 
holds).

Jim

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