[Coco] MPI replacements?

[Little John (GIMEchip.com)]

Agreed. I believe it would be best to stick with the suggestions of SMD TTL. 
Also, I've noted that the transistor circuit that I had intended to power on 
the ATX supply probably will not work. It needs to be modified so that the 
collector voltage is from 5VSB of the ATX supply and the base drive should 
be from 5V of the CoCo for it to properly function (I think).
-John

----- Original Message ----- 
From: <jdaggett at gate.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Saturday, July 10, 2010 4:51 PM
Subject: Re: [Coco] MPI replacements?


> The CPLD route is not all the panecia that it is cracked up to be. ALmost 
> all new CPLDs are
> no longer 5 volt tolerent. SOme are still around that both input and 
> output will drive 5 volt TTL
> logic. They are expensive. Some of the newer less costly CPLDs need level 
> translation to
> properlydrive 5 V TTL loads as well as inputs.
>
> just a thought
> james
>
> On 10 Jul 2010 at 3:00, Little John (GIMEchip.com) wrote:
>
>> Putting the whole thing in a CPLD would be the most flexible method. It
>> would allow entire restructuring of the device on the fly. I'll decide 
>> soon
>> as to how to proceed - I'm currently engrossed in the memory upgrade, 
>> which
>> is being problematic (human error, but I shall not give up)
>> Thanks All - John
>>
>> ----- Original Message ----- 
>> From: "Phill Harvey-Smith" <afra at aurigae.demon.co.uk>
>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>> Sent: Saturday, July 10, 2010 2:29 AM
>> Subject: Re: [Coco] MPI replacements?
>>
>>
>> > On 09/07/2010 21:15, 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.
>> >
>> > The problem with using a Rom or a GAL/PAL is that you need an external
>> > programmer to program the logic into them. Programmers for these 
>> > devices
>> > are generally quite expensive.
>> >
>> > The advantage with a CPLD is that they are generally in circuit
>> > programmable with a cable that can be purchased or made relatively
>> > cheaply. Also it makes changing the logic much easier. They are
>> > generally available in PLCC (such as the Xilinx 9536/9572/95108 and the
>> > XL versions) which means they can be socketed and don't then need any
>> > surface mount soldering.
>> >
>> > Just my 2p/2c :)
>> >
>> > Phill.
>> >
>> >
>> > --
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>>
>>
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