[Coco] MC6847 External Character ROM

[John W. Linville]

On Tue, Jan 20, 2015 at 06:06:49AM +1000, Nick Marentes wrote:
> On 20/01/2015 5:52 AM, John W. Linville wrote:
> >You'll be limited to one of two 2-color options with these "graphics",
> >of course.  It could still be interesting, but it looses some luster
> >when you have to choose between light green & dark green or light
> >orange and dark orange... ;-)
> >
> >John
> 
> That's for characters up to 128. Can the characters 128 to 255 (8 colors
> block graphics) also not be reprogrammed?

The colors don't come from the ROM data.  The high bit of the data
in the RAM is fed back into the VDG to select the semi-graphics mode,
so the color and the encodings are all internal to the VDG.

> Even so, hires graphics, even only light and dark green, would make VDG text
> displays so much nicer... and it only eats 512 bytes!

It could be cool, yes.  Just not as cool as one might think at first. :-)

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.