[Coco] Simple 8-bit VGA Graphics Card

[Kip Koon]

Hi Fedor!
The biggest part of my heritage is German, but having been born in the
United States, I sadly never learned anything but American English such as
it is.  Thank you very much for helping me with the translation from German
to English for this little project.  I'm also looking at two other video
controller possibilities. One uses an Atmel processor for the video
controller in a 6502 based computer called Veronica and the other called
F18A uses a Xilinx chip mimicking a TMS9918A video display processor while
being pin for pin compatible with the original TMS9918A chip with many
improvements added to the original chip's capabilities.  All three solutions
are very interesting.  This simple 8-bit video controller version which uses
the Xilinx XC9572 CPLD is the most interesting (at this point in my young
life as a hardware developer anyway) in that all video memory is accessible
using only 3 memory mapped registers.  The fourth memory location is
undefined and unimplemented but takes up a memory location nonetheless.  I'm
hoping that because of this layout, and the similarity (though not exactly)
to the coco's original video resolution, that is may be quite a bit easier
to integrate it into the original CB, ECB and DECB code.  Later I might look
at the other more advanced designs after I get a bit more experience under
my belt.  I'm sure this project will be quite involved and interesting.  I
originally said I was not interested in graphics for my little 6809/6309
computer,  but I can definitely see the advantages.  Maybe this could
eventually become the 4th Coco that we all so desperately want.  Any and all
help and assistance is most graciously accepted.  Though much desired, I
think the copyright on the code could become a problem if this were to
eventually become a commercial product.  Even though Tandy Radio Shack,
Microsoft and Microware all have various parts of the code copyrighted,  I'd
still like to see this project become fully realized.  Besides, I never
could afford building my own 6809 based computer back in the 1970s and 1980s
when the computer revolution was actually taking place.  When I finally
found out about the various "personal computers" in kit form, it was too
late.  They had already become history.  But now, I actually have the
opportunity to realize my dream using as many modern chips as possible and
further my understanding of 8-bit computer hardware designing at the same
time.  :)  Anyhow, I am very interested to be working with you on this
little project of mine.  Thanks again.
Kip

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of Fedor Steeman
Sent: Monday, January 28, 2013 9:30 AM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] Simple 8-bit VGA Graphics Card

Hi!

Sounds neat! I can help out with the German. I will take a look. We haven't
heard from Torsten Dittel for a while, so I assume he is absorbed by his
young family lately.

Cheers,
Fedor Steeman

On 28 January 2013 03:09, Kip Koon <computerdoc at sc.rr.com> wrote:

> Hello My Fellow Cocoers,
>
> In the course of the development of my 6809 computer, several people 
> have suggested that I add a video controller.  Well, I found one that 
> looks very interesting and quite simple, only the guy speaks German, 
> so if anyone knows German, I’d like to ask that person to translate 
> the documentation in the zip files.  The link below is via Goggle 
> translator, so I can read the web page with ease.
>
> http://translate.google.com/translate?sl=de
> <
> http://translate.google.com/translate?sl=de&tl=en&js=n&prev=_t&hl=en&i
> e=UTF
>
> -8&layout=2&eotf=1&u=http%3A%2F%2Fwww.ulrichradig.de%2Fhome%2Findex.ph
> p%2Fcp
> ld%2F8bit_c_graka>
>
> &tl=en&js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.
> ulrich radig.de%2Fhome%2Findex.php%2Fcpld%2F8bit_c_graka
>
> The following info is from a file in the zip file in German.
>
>
>
> DatenBus Steckerbelegung
>
>
>
> Pin          Funktion
>
> 1              Daten1
>
> 2              Daten0
>
> 3              Daten3
>
> 4              Daten2
>
> 5              Daten5
>
> 6              Daten4
>
> 7              Daten7
>
> 8              Daten6
>
> 9              A1
>
> 10           A0
>
> 11           N.C.
>
> 12           WR
>
> 13           GND
>
> 14           VCC (+5V)
>
>
>
> It looks quite straight forward.  So far I figure that the input lines 
> to the video card are 8 data bits, 2 address bits, a write bit, ground 
> and +5 volts.  Really a very simple interface.
>
>
>
> Another file has the following.
>
>
>
> 8 Bit Grafikkarte für µC
>
>
>
> Garfikkarte hat eine Auflösung von 256x256Pixel mit 32Farben (6Bit)
>
> Unterstützt 60Hz mit 32MHz Quarz und 75Hz mit 40Mhz Quarz im 
> Auflösungsmodus
> 640x480
>
>
>
> Adressen:
>
>
>
> Register 0 = Pixel in horizontaler Richtung (8Bit) Spalte
>
> Register 1 = Pixel in Verticaler Richtung (8Bit) Zeile
>
> Register 2 = Farbe (6Bit)
>
> Register 3 = not use
>
>
>
> Looks like it’s 256 bits x 256 bits x 32 colors using a 6 bit digital 
> to analog converter.
>
> A horizontal frequency of 60Hz with a 32MHZ crystal and 75Hz with a 
> 40MHz crystal.  The result is a 640 by 480 VGA screen.
>
> Register 0 is the horizontal pixel to be accessed.
>
> Register 1 is the vertical pixel to be accessed.
>
> Register 2 is the color to be written to the above addressed memory 
> location.
>
>
>
> The really nice thing about this interface is the custom video 
> controller chip which has its own 64KBs of memory.  No need (yet) for 
> my computer to have a copy of the video info stored in the computer’s 
> main memory, however if I am to merge the graphics commands back into 
> Grant’s 6809 Extended Basic, I’ve got my work cut out for me.  J  More 
> fun, Yes!  I’m really thinking seriously of implementing this simple VGA
video controller.
>
> I’ll leave the rest for you guys to read on the web site and in the 
> downloadable zip file.  I’m sure I’ll come across other video 
> controllers and I’m sure you guys have ideas too for a video 
> controller of your own for a 6809 8-bit microprocessor based computer
system.  Have Cocoing & 6809ing!
>
> Kip
>
>
>
>
> --
> 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