Good Composite->VGA converters for classic computers (& video

Tony Duell ard at p850ug1.demon.co.uk
Wed Jun 4 21:43:40 CDT 2008


> 
> Tony Duell wrote:
> >> Just picked up a Wei-Ya ACV-011 CGA --> VGA converter board with the 
> >> intention of using it with a Commodore 128 (and possibly Amiga).  It 
> >> doesn't have a true TTL input, but there is a C128 enthusiast out there 
> >> who published a small circuit to do the RGBI --> CGA interface.
> > 
> > Err, what is a 'CGA Interface' if not a TTL-level RGBI one?
> 
> Don't know, but remember how the 5153 has special circuitry that turns 
> color index #6 brown?  I don't think any converter anywhere would handle 

Hmmm...

If the input to the converter is a 4-bit TTL level thing, that as far as 
I can see no external circuit could correct the 'brwon problem'. After 
all, all 16 possible states of the 4 lines are used.

However, other messages make be think that the input to the coverter is 
actually analogue RGB at TV rates. The sort of thing you get out of a 
(UK) DVD player, for example. In which case I can see the need for an 
interface to conenct it to a 4-bit RGBI connector (at the same scan 
rates). 

But I wouldn't call an analouge RGB inteface 'CGA'.

-tony



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