[Coco] Video band width and accessing video memory

[Dave Philipsen]

Here’s a snippet from the CoCo3FPGA manual that explains how it works:

The default 256 colors are contained in an internal RAM block in the FPGA. Because they are in RAM, they can be changed. This means the 256 color palette can be changed. To change one of the 256 colors, write the desired 12 bit color data into Palette 0. Then write the color number that is to be changed into IO address $FF7E. The color contain in Palette 0 will be written into the 256 color RAM at the address specified in IO location $FF7E.

Dave

> On Jun 3, 2019, at 4:46 PM, L. Curtis Boyle <curtisboyle at sasktel.net> wrote:
> 
> Is that using the “standard” fixed 256 color palette, or with a way to select from a >256 colors? If the latter, how is that mapped into the Coco palette register space?
> 
> L. Curtis Boyle
> curtisboyle at sasktel.net
> 
> 
> 
>> On Jun 3, 2019, at 3:40 PM, Dave Philipsen <dave at davebiz.com> wrote:
>> 
>> Yep, in theory they are supported on the CoCo3FPGA. The only 256-color mode I’ve use on it is the 640x450. And I believe Gary has already implemented the 256-color 160x192/200/225 mode and, I assume, the 128x192/200/225 mode on GIME X.
>> 
>> Dave
>> 
> 
> 
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