I don't the crummy composite video on Hummer Racing and DTV R2 & 3. Is there any way to get digital RGB for use with R2R ladders or RAM DAC?
Sincerly,
Meggan Scavio
Los Angeles, California
You can use the 4 luma bits without a problem, but the 4 chroma bits need special initialazation.
The color subcarrier for chroma is generated by a digital frequency synthesizer(DFS) and phase shifted by adding the 4 bit value in color look up table.
To get meaningful values from chroma you'll need to precisely stop the DFS when outputing "0000" and set saturation to maximum("11")
Stopping DFS at "000":
Set all three burst rate registers to "00000000".
Set PhaseAlternate to '0' .
Set Burst Lock to '1' (Bit[2] $d04f) until after burst on odd line(LSB Raster = '0')
Set burst lock to '0' before burst on even line.
The DFS is now flooded with 0's, stopped and you'll now see chroma values in the CLUT reflected in the chroma pins.
H and V Sync can be extracted with any low cost sync separator(lm1881) .
Now you can hook it to a digital RGB monitor, R2R ladder or RAMDAC.