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

[Zippster]

Especially if you hit the surplus market, where you can find some very good deals
on common CPLDs.  Not too long ago I scored 500 9572XL VQFP-64’s for ~10 cents
each, in trays, sealed.  That’s the exception, but a buck or so for that part is not so unusual,
and it can replace a lot of TTL.

Being able to alter much of the design after production without any board changes as you
mention is a HUGE plus, allowing fixes and improvements after the fact.

Once you get past the learning curve on using them, I don’t know how anyone wouldn’t
like CPLDs, except for the purity thing, which I do get.  The 5v tolerant ones are ideal for
interfacing to these old machines.

- Ed


> On Aug 2, 2017, at 7:47 PM, RETRO Innovations <go4retro at go4retro.com> wrote:
> 
> On 8/2/2017 7:40 PM, Zippster wrote:
>> Well that’s just like…  using a nuke to swat a fly!   :)
>> 
>> Seriously though, while I wouldn’t put a CPLD on a board just to interface that TI chip,
>> a small one isn’t necessarily (severe) overkill even on just a ROM cart with a sound chip.
>> 
>> Considering you can handle your address decoding, add a couple of registers and some
>> banked flash ultra easy at the same time, while reducing overall chip count.
>> 
>> I do understand that some people enjoy simple solutions and keeping the components
>> old school though, and I can respect that.
>> 
>> I just love mixing the old and new together myself.
> For me, it's economics. Sadly, TTL are starting to be $.25-.50/unit, and by the time you've put 4 or so on the board, you're sliding into xc9536xl or 9572xl costs, offering more functionality and a chance to fix a mistake after production, at no additional cost.
> 
> As Ed notes, it's not "pure" (though GALs and such existed in the 80's), but I've yet to see someone turn a design away because it had newer components on it.
> 
> Jim
>