[Coco] Coco proto board

[Gene Heskett]

On Friday 14 September 2007, Mark McDougall wrote:
>Hi,
>
>I'm toying with the idea of producing a coco 'prototype' board that plugs
>into the cartridge connector slot.
>
>I'm thinking of putting a MAX3000A CPLD on there to handle both address
>decoding and allow programmable I/O. It will also have a ROM socket and a
>'proto area'. Build option will be clocked by E/Q or on-board clock.
>
>Question:
>
>Which address lines should I route to the CPLD for decoding? I was
>thinking perhaps the top few lines and the bottom few... what would be the
>best mapping options for such a board?

As most of the stuff the coco used needed its i/o in 4 byte wide hunks, I 
think I'd use the 14 most significant address lines, and if doing other i/o, 
all 16.  But the logic for the individual device enables would do with just 
the top 14.

>And any other options that would be nice?

Yes, a kit to replace the shacks own broken decoders in the coco proper.  
Having the whole $FF00-$FF1F block tied up for one pia that needs 
$FF00-$FF03, and again from $FF20 -$FF3F for the other pia that actually 
needs $FF20-$FF23 was a short cut that should have been nipped in the bud 
before it ever saw production in the first gray ghosts.

>FYI: we're getting another (non-coco) PCB (2-sided) done and I thought we
>could fill out the panel with a handful of these boards... so it's not
>definite yet... just a thought atm...

Looking at the MAX3000A's pdf, I assume theres a 'password' to get into this 
chip for programming purposes?  I didn't see it in a 1 minute scan.  If so, 
can the coco itself program this chip?  That would be very neat.

How large a device did you have in mind?

>Regards,



-- 
Cheers, Gene
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