A.D.A. Amiga Demoscene Archive

I tried to code a vertical screensplit with two HAM8 160x256 pixel pictures. The first (left) one should colour 0-64 the second one colour 64-127.
But the colorswitching doesn't work. The colours 64-127 are not used. After the switch with the value 64 the second (right) HAM8 picture uses the colours 0-63 but not in the right order.
Funnily enough the same routine works fine on a Screen with 128 colors and 7 bitplanes. The first picture uses colours 0-127 the second one colours 128-255.
So what can I do ? Or in other words is the use of colorswitching via the bplcon4 register really possible on HAM8 screens?

Completion to Colorswitching via BPLCON4 in HAM8-Mode

Meanwhile I tested the colourswitch on a HAM6 screen. It is apparent that the content of the BPLCON4 register is totally ignored when you change it every scanline with the copper. The second (right) picture uses exactly the same palette (colours 0-15) as the first (left) one.
I know that HAM pixels behave different than normal pixels but strange that it doesn't work. I thought selecting a colour value from a colour registers by the value 00 in the modify planes works the same way as on standard screens. Messing up the palette of the second picture on a HAM8 screen seems to be a side effect using plane 0-1 for modify and not plane 6-7.

Pity it doesn't work. Is it on a real Amiga or on WinUAE?

Hi rload,

it's on a real Amiga 1200. I haven't tested my routine on WinUAE yet.

A few quick checks:

- e-uae sourcecode confirms that both ham8 and ham6 modes ignore the xor value stored in bplcon4.

- minimig doesn't support aga, so there is no trace of bplcon4