Commodore Amiga A1000, Hardware Reference Manual

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Table 3-3: Contents of the Color Registers
Bits
Bits 15 -12 Unused
Bits 11 - 8 Red
Bits 7 - 4 Green
Bits 3 - 0 Blue
Table 3-4 shows some sample color register bit assignments and the resulting colors. At
the end of the chapter is a more extensive list.
Table 3-4: Sample Color Register Contents
Contents of the Resulting
Color Register Color
$fff White
$6fe Sky blue
$db9 Tan
$000 Black
Some sample instructions for loading color registers are shown below:
LEA CUSTOM,a0 ; Get base address of custom hardware...
MOVE.W #$FFF,COLOR00(a0) ; Load white into color register 0
MOVE.W #$6FE,COLOR01(a0) ; Load sky blue into color register 1
NOTE
The color registers are write-only. Only by looking at the screen can you find out the
contents of each color register. As a standard practice, then, for these and certain other
write-only registers, you may wish to keep a "back-up" RAM copy. As you write to the
color register itself, you should update this RAM copy. If you do so, you will always know
the value each register contains.
SELECTING THE NUMBER OF BIT-PLANES
After deciding how many colors you want and how many bit-planes are required to give
you those colors, you tell the system how many bit-planes to use.
- Playfield Hardware 41 -