[Coco] External CHAR ROM for 6847

[RETRO Innovations]

On 10/20/2024 3:40 PM, Dennis Bathory-Kitsz via Coco wrote:
> As I said in my private email to you, I have little recollection of
> what I did 40+ years ago -- and after GMM failed, I was done with
> computer stuff. Het was voorbij, as the Dutch would say.
UNderstood.  Well, I enjoy figuring these things out, so I'll continue
researching.
>
> I recall only that the datasheet had partial bits of a design. Since
> mine was the first go at a lowercase mod, I had to find my own way to
> make it work.

That helps.  The datasheet used a 74LS161 to clock the CHAR ROM, but you
used a 7493 (no load) and a 74'73 flip flop, so I am trying to
understand the rationale there.  Might be just two ways to do the same
thing...

Understanding the ROM files also helps, and I found some of the binary
files from the various character generator ZIP files on the archives.  I
wrote a quick and dirty app to try to parse them, but having some issues
with some of the "meta" data in the files.  If anyone is up for a
forensic challenge, the files are here:

https://github.com/go4retro/lowerkit

As you can see in the charsets dir, the .txt files show most of the
characters, with what looks like 4 bytes of information before each
character.  But, sometimes, there is more than 4 bytes before a char,
still trying to figure that out.  Folks can grab the repo and recompile
the main.c and re-run the extract tool on Mac, Windows, Linux (I put the
Win64 EXE in there)

Obviously, if anyone has a lowerkit and can dump the various ROMs,
that'd be nice as well.  They should be archived, if nothing else.

Jim

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