[Oberon] FPGA - Display.Mod 4-bit colour

Tomas Kral thomas.kral at email.cz
Tue Oct 16 14:57:11 CEST 2018

On Tue, 16 Oct 2018 01:26:45 +0200
Tomas Kral <thomas.kral at email.cz> wrote:

> Noticeably, Display does not seem to have the same intensity down
> across, at the the 1/3 upper top appears slightly darker.


This seems a matter of vision angle, I have tried to leave out
hsync/vsync signals just for the thrill of it, than indeed picture is
dark at the top of the screen.

So is probably right what is does, except I cannot decide on the
palette map. In RGB triplet, leftmost byte influences RED most,
middle green, and last blue. But looking at the map entries, it appears
as if the other way round.

$000080H displays as deep red, while I would expect blue.

Another thought, in `Display.Mod' I can see,
CONST black* = 0; white* = 1(*5*);  (*black = background*)

Now white may become 15, $FF or -1 in other terms. But changing it
would require rebuilding other system modules.

I have added in the Top module, a simple `IF' instantiating second map
index based on the mode. Not sure if brightest idea.

I wish to add two procedures to manipulate the map SetMap(), GetMap(),
but where?

`Display3.Mod' might be the option or non-existent Display2. 

I thought Display3 not only provides simple graphics primitives
polygons, rectangles, etc but also acts as underlying functionality for
Gadgets, correct?

What other functionality of Display3 makes sense porting to RISC?

Thank you for reading this.

Tomas Kral <thomas.kral at email.cz>

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