[Coco] DS-69 Digisector Dissection (Was: Re: IO ports Re: (no subject))

Joel Ewy jcewy at swbell.net
Sat Nov 17 11:22:26 EST 2007

Joel Ewy wrote:

I might add that I was able to generate logic equations from the JEDEC
dumps of the GALs, and I still have those files, dated 6/15/1994. 
Doggonne-it, this has re-piqued my interest.  I don't have time for this.

> Willard Goosey wrote:
>>> Date: Fri, 16 Nov 2007 21:01:32 -0600
>>> From: Joel Ewy <jcewy at swbell.net>
>>> The DS-69[B] Digisector video digitizer contains a 68[B]21 PIA starting
>>> at FF70.  
>> Hey, cool.  More stuff for the list!  Maybe sometime soon I can update
>> my IO list.
> I've always been fascinated by this darn thing (the DS-69) and have done
> a little work in the direction of reverse-engineering it.  Back in the
> day I had the idea of cooking up some software that would allow one to
> digitize in OS-9.  I drew out a partial schematic at one time (the
> double-sided board is translucent), and IIRC, the socketed GALs didn't
> have their security fuses blown, so into the programmer they went for a
> good reading.  More recently I disassembled the little ML program that's
> supposed to allow you to digitize from BASIC programs.  But I ran into a
> rather mysterious chunk of code, which I posted on this list.  I had
> never really used the example BASIC programs, but when I tried out the
> one that purports to digitize in 64 levels of gray, I got garbled
> results.  I now believe that The Micro Works distributed buggy code.  So
> now I may need to disassemble the much larger, more complicated C-See
> program rather than the simple subroutine, if I want to figure out how
> this thing really works.
>> Willard
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