[Coco] MPI replacements?

[Little John (GIMEchip.com)]

James,
I have had several people suggest that I redo the design using a single PCB 
rather than the two. This is a good idea.

I wanted to use a CPLD to put the whole thing into, but a couple of 
different folks suggested that SMD 74xx series would be preferable and I'm 
thinking they are right.

There is a GAL in the design to determine when to enable the data buffer, 
but even this could be done in discrete logic, though I will keep the GAL 
because it allows me to economically add a few extra features, such as a 
jumper to enable the $FF8x range if desired, as well as enabling writes to 
$FF0x (so external user peripheral devices could receive data that is 
written to the PIA) - this would be write only, otherwise contention would 
result on reads of the PIA. The $FF1x area can be enabled for both reads and 
writes (on a CoCo 1 or 2, this should only be enabled on writes, or not at 
all, On a CoCo 3 this area is available for read and write), $FF2x (same 
conditions as $FF0x), $FF3x (same conditions as $FF1x) and so on - the idea 
is to create the most flexible MPI replacement possible while still allowing 
100% compatibility with the Tandy MPI.

I have also decided to release all of my projects as completely open and 
allow others to manufacture & sell them if they so desire, Royalty free. I 
started this venture to benifit the entire CoCo community, and to keep my 
mind off being sick. It's win-win for me and hopefully all of you folks as 
well.

In the long run, I would like to design a replacement CoCo 3 motherboard 
with built-in slots and an ATX form factor - a GIME would be all that would 
need to be plugged in - which means a deceased coco 3 would be needed to 
snag the GIME. Now, this project is more likely to never reach completion 
that to be completed - it's a lot of work, but if there are any folks who 
want to start a design team - I'm all in - just give me a holler (that's 
southern talk Y'all) :-)

I'm always spending almost all of my waking hours working on this stuff, and 
when I get stuck, Dad helps (yeah - I haven't done all of this work by 
myself - I've had help - it's just my determination to see this all thru)

Thanks Guys (and Ladies) - if you have ideas for designs - pitch them to 
me - I'm always glad to help.

-John



----- Original Message ----- 
From: "James Dessart" <skwirl42 at gmail.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Friday, July 09, 2010 11:19 AM
Subject: Re: [Coco] MPI replacements?


> On Thu, Jul 8, 2010 at 6:54 PM,  <jdaggett at gate.net> wrote:
>> How small is small?
>
> Ideally just the board, connector for the CoCo, edge connectors for
> the individual cards and a connector for an ATX power supply, to fit
> into an ATX case or whatever for a repack. If anything needs switches,
> movable jumpers would be fine.
>
> The idea is to make my CoCo system take up as little space as
> possible, so I'd probably be adding an RGB converter and whatever I
> can to reduce system footprint.
>
> -- 
> James Dessart
> <http://ideaoubliette.blogspot.com/>
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco


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