[Coco] MPI replacements?

[Rob Rosenbrock]

Never mind... Without knowing more about the specifics, I think I jumped in a bit soon.

On Jul 9, 2010, at 4:15 PM, Rob Rosenbrock wrote:

> Rather than a GAL or discrete logic, have you ever considered using a small ROM? I've seen one implemented utilizing it as a truth table.
> 
> At least I think a small 1K x 8 ROM should still be available...
> 
> On Jul 9, 2010, at 3:20 PM, Little John (GIMEchip.com) wrote:
> 
>> 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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> 
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