[Coco] COCO Video

[Mike Pepe]

John, if anyone should have seen it in breadboard form, it should have been
you!

-Mike

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of john dumas
Sent: Wednesday, June 19, 2013 6:34 AM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] COCO Video

On 6/19/2013 2:39 AM, T. Franklin wrote:
> I think you're confusing the 6847 with the GIMI. The 6847 was a chip
Developed by Motorola for a dumb terminal called TRS-80 VideoTex Terminal,
for the farm industry (precursor to the CoCo). The GIMI was breadboarded
with discrete components when developing the CoCo3.
>
> https://en.wikipedia.org/wiki/TRS-80_Color_Computer
>
>
>
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>
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>
> The logic of the 6847 is relatively simple and constructing a
replacementfor it isn't outside of the realm of possibility. The thing was
breadboardedwith discrete logic while being designed, after all.
If there was a breadboard of the VDG, it was well hidden from the folks at
the Austin Design Center! While doing the Time Domain Analysis of the VDG, I
would have LOVED to have a breadboard to compare with some of the race
conditions and the one logic error, I found....and had to correct.

A breadboard would also have very useful while testing the first silicon. If
such a BB existed, I wonder WHERE it lived? Has anyone actually seen it with
their own Mark One eyeballs?

Oh and BTW, a BB would have prevented the surprise we got when the first
silicon powered up in one of the two "modes" - green or orange
background......I remember the "What the...!"
expressions. Seems that all of us designers involved with the chip missed
that "feature"
before finalizing the design.
My bad!


cheers,
johnd

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