[Coco] MC6847 External Character ROM

[John W. Linville]

On Sat, Jan 17, 2015 at 03:39:43PM +1000, Nick Marentes wrote:
> On 17/01/2015 12:15 PM, Luis Antoniosi (CoCoDemus) wrote:
> >I a nice improvement would be using SRAM and allowing the coco to change it
> >on the fly using some port. The SRAM would be dumped from ROM upon reset.
> >
> >Just in case you end up without any other project ;)
> >
> >
> >
> 
> You took the words right out of my mouth Luis!
> 
> Why just a ROM with a fixed character set when you could add some SRAM and
> give the CoCo1/2 the ability for a programmable character set (or PCG
> graphics).
> 
> It would be possible to create 256x192 graphics on a screen that only
> occupies 512 bytes!  And it would be fast.
> 
> Several computers of the time had this and I was always dissapointed that
> the 6847 VDG wasn't designed with this capability.

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