4 Jun
2008
4 Jun
'08
4:19 p.m.
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?
Most of what are currently called "CGA->VGA" converters are analog RGB
input at CGA/NTSC frequencies to (scan converted) analog RGB output at
VGA frequencies. Which is a good thing because they are build for the
(much larger) classic video game market so they are more veratile than
a strict CGA->VGA converter would be.
S\o you need a small circuit to mix I with the RGB to get an a 3 level
(0,0.5,1) signal that these boards can understand. You could easily
add a "yellow->brown" converter to this circuit by pulling down the
appropriate lines in a resistor divider when color #6 shows up. It
would add 1 chip and two resistors to the design (off the top of my
head).
Eric