Re: Help w/ NEC Multisync 3d and TTL

[David Wilson <mcs6502@gmail.com>]

On Mar 3, 5:01 am, Steven Hirsch <snhir...@gmail.com> wrote:
> The service manual lists the following signals as being valid when in TTL
> (EGA/CGA) mode:
>
> RA GND
> r
> R
> g
> V.D
> H.D
> G
> B
> b
>
> So, what is that trying to convey?  The V and H sync are somewhat obvious, as
> are R,G,B.  So, what are the lowercase r,g,b? Inverted polarity?  Different
> levels?

An EGA-compatible color monitor is driven by six color signals - three
primary (higher intensity) and three secondary (lower intensity). All
64 combinations of these six signals appear as different colors or
intensities or both.

In other words:

R r G g B b Color
0 0 0 0 0 0 Black
0 1 0 0 0 0 dark red
1 0 0 0 0 0 medium red
1 1 0 0 0 0 bright red

and similarly for the Gg and Bb pairs.

> Is "RA GND" just simply ground or is it something else?

As it is the only ground, it must be simply ground for all the color
and sync lines. According to my reference books:

EGA pinout (DE-9)

1 Gnd
2 S.red
3 Red
4 Green
5 Blue
6 S.green
7 S.blue
8 H drive
9 V drive