[Oberon] FPGA - Colour Support

[Tomas Kral]

Hi,

I have coded an initial version of B&W bitmaps for `Pepino' (some
further improvements pending to push to git), now working on pictures. I
wish to also make some progress with colour support. I have got these
two mods for `vid.d' kindly provided by Magnus.

// 3-bit colour
wire vid_R, vid_G, vid_B;
assign RGB = {vid_B, vid_B, vid_G, vid_G, vid_G, vid_R, vid_R, vid_R};

// 4-bit with colour map
input [23:0] col0, col1, col2, col3,
input [23:0] col4, col5, col6, col7,
input [23:0] col8, col9, col10, col11,
input [23:0] col12, col13, col14, col15,
assign RGB = {color[23:21], color[15:13], color[7:6]};

The above would require `Display.Mod' be completely rewritten.

I was therefore thinking of an implementation as described in the PO2013
chapter on Display, where there are three distinct bit planes, one
for B&W, and the other two for colour. 

`Display.Mod' will work as is, and adding colour means to write to other
colour planes.

What do you think? How difficult is it to implement?
Can it be made as memory efficient as 4-bit colour maps above?

Many thanks so far.

-- 
Tomas Kral <thomas.kral at email.cz>