[Coco] RE: [Color Computer] Re: VHDL 6809
Paul T. Barton
idezilla at yahoo.com
Fri Mar 26 16:52:53 EST 2004
--- John Kent <John0457 at hotmail.com> wrote:
What I had in mind was to use a non interlaced
RGBI output rather than the composite video
produced by the 6847. That way you could use a
standard PC monitor. The only tricky bit then is
the various graphics modes. The character
generator is not a big problem, but adapting the
scan rate to a PC monitor might be.
I got my VHDL 6809 running with a 12.5MHz E
clock. That is over 10 times faster than the
original CoCo. It means that I can run higher
screen resolution although that would be
incompatible with the original CoCo. The SAM
multiplexes Memory between the CPU and Video
display. 16 bits at 12.5MHz should give you 80
characters across with 256 colours at a 32KHz
The FPGA board I'm using allows for up to 64
colors as it only uses 6 bits to the RGB DAC (2
bits / colour). I am half way through designing a
text based VDU for it.
Any chance that you would release the VHDL
to this community?
I'd like to put it into a Lattice part.
Paul T Barton
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