[Coco] An 8-Slot Multi-Pak Design for my Color Computer Friends

[Little John (GIMEchip.com)]

Had to have a fourth of July Holiday, so now I'm back. Let's have a look 
see:

> First
>
> A huge mistake in not buffering the data bus on the main board. If you are 
> running a stock
> Coco3, you do run the risk of damaging the MC6809E and the HD6309E if the 
> board
> becomes detached while powered up.
>
That's easy enough to fix. However, even with the databuffer on the main 
board, detaching while powered up could cause damage, especially if it were 
knocked sideways - zap.

> Second
>
> why the dip switches on the Control and clock lines. A wrong setting on 
> the dip switches and
> you have a nonfunctioning board that can lead to frustration.
>
If I build it, I'll know what the DIP swicthes do. But again easily fixed - 
jumper wires instead of the DIP switches if you don't want the DIP switches.

> Third
>
> What is the function of Q1?
>
It is supposed to tell the ATX power supply to switch on when the CoCo 
Powers on - this was stated in the text. However, this is pretty lame - A 
reed relay might have been better or just a switch to turn the darned thing 
on. Yeah - the switch probably would be best.

> Fourth
>
> Your ground plane on the top and bottom are basically floating planes that 
> are tied at but just
> a few spots. You have all your locic tied to GND1 and then this large 
> plane on both sides is
> GND. You also have fingers that are floating that is bad for noise 
> immunity. Either use one
> ground or tie them in a star pattern and eliminate the floating fingers.
>
> just a few things I see wrong or bothersome.

I did use only one ground - the GND/1 is the Library Name for the Ground 
Symbol that I have chosen - ALL Grounds in the schematic are electrically 
tied to the GND net name. This can be seen if you load it up in EAGLE and 
right click to get the properties of any GND connection - they are all tied 
to GND.


If you find any more problems - fire away - it'll help me fix this right up. 
I'm just a hobbyist - no formal training, so this design MUST be SCRUTINIZED 
thoroughly in order to work out all of the bugs. -John

----- Original Message ----- 
From: <jdaggett at gate.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Sunday, July 04, 2010 5:09 PM
Subject: Re: [Coco] An 8-Slot Multi-Pak Design for my Color Computer Friends


> First
>
> A huge mistake in not buffering the data bus on the main board. If you are 
> running a stock
> Coco3, you do run the risk of damaging the MC6809E and the HD6309E if the 
> board
> becomes detached while powered up.
>
> Second
>
> why the dip switches on the Control and clock lines. A wrong setting on 
> the dip switches and
> you have a nonfunctioning board that can lead to frustration.
>
> Third
>
> What is the function of Q1?
>
> Fourth
>
> Your ground plane on the top and bottom are basically floating planes that 
> are tied at but just
> a few spots. You have all your locic tied to GND1 and then this large 
> plane on both sides is
> GND. You also have fingers that are floating that is bad for noise 
> immunity. Either use one
> ground or tie them in a star pattern and eliminate the floating fingers.
>
> just a few things I see wrong or bothersome.
>
> By the way I have a degree in Electrical Engineering and have 23 yrs 
> experience in PC layout
> and design of portable electronics. SO these questions do come from 
> someone that has
> experience and questions about the design.
>
> james
> On 3 Jul 2010 at 18:12, Little John (GIMEchip.com) wrote:
>
>> This is my latest project, designed just for you guys and the readers of 
>> CoCo3.com. I worked on this for about 9 hours when my internet was off. 
>> Hopefully it will be of some use to some of you.
>>
>> It is taking a lot longer to do the write up than it did to complete the 
>> design, but I have posted Part 1 (of 2) here:
>> http://www.coco3.com/community/2010/07/this-is-part-1-of-2-of-an-8-slot-mpi-multi-pak-interface-design-for-my-friends-at-coco3-com-andor-the-maltedmedia-list-members-from-your-friend-johngimechip-com
>>
>> Let me know if you spot any potential problems. I'll get part two typed 
>> up and posted by tomorrow.
>>
>> Enjoy. Let me know if you find any errors in my design. I'll fix any that 
>> crop up.
>>
>> Your Friend - Lil' John
>>
>> --
>> Coco mailing list
>> Coco at maltedmedia.com
>> http://five.pairlist.net/mailman/listinfo/coco
>
>
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco


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