Goblin-King wrote:wut? NES can show 25 colours at a time?!
You wouldn't know this from looking at most games.
Do you know of an official game which really utilizes this?
I want to check it out
Forgot about this. Here, this is the best I can do--a descriptive analyis. I do not know if any games did use them all, but they could have.
"PPU Palettes
------------
PPU 3F00h-3F1Fh - Background and Sprite Palettes
Palette Memory (25 entries used)
3F00h Background Color (Color 0)
3F01h-3F03h Background Palette 0 (Color 1-3)
3F05h-3F07h Background Palette 1 (Color 1-3)
3F09h-3F0Bh Background Palette 2 (Color 1-3)
3F0Dh-3F0Fh Background Palette 3 (Color 1-3)
3F11h-3F13h Sprite Palette 0 (Color 1-3)
3F15h-3F17h Sprite Palette 1 (Color 1-3)
3F19h-3F1Bh Sprite Palette 2 (Color 1-3)
3F1Dh-3F1Fh Sprite Palette 3 (Color 1-3)
Palette Gaps and Mirrors
3F04h,3F08h,3F0Ch - Three general purpose 6bit data registers.
3F10h,3F14h,3F18h,3F1Ch - Mirrors of 3F00h,3F04h,3F08h,3F0Ch.
3F20h-3FFFh - Mirrors of 3F00h-3F1Fh.
Palette Entries
Bit7-6 Not used (contains garbage when reading palette memory)
Bit5-4 Luminance (Grayscale) (0-3)
Bit3-0 Chrominance (Color) (0-F)
The Color values are based on the NTSC color-wheel (even on PAL consoles):
|__0__|__1___2___3___4___5___6___7___8___9___A___B___C_|_D__|__E___F__|
|White|..Blue..Magenta..Red......Yellow...Green....Blue|Gray| Black |
Color and Grayscale (0-3) can be combined as such:
Luminance__0Xh_______1Xh__________2Xh_________3Xh___________________
Color 0: Med Gray, Light Gray, White, White
Color 1-C: (Dark), (Normal), (Brighter), (Brightest/Pastelized)
Color D: Reserved, Black, Dark Gray, Lighter Gray
Color E-F: Black, Black, Black, Black
Some black/white colors are duplictated, one should normally use 0Eh or 0Fh as
black. Of the two Light Grays, 3Dh is slightly brighter than 10h. The Reserved
color is Blacker-than-black, producing a very low voltage, which some monitors
may or may not treat to be a sync signal rather than a color.
Monochrome Television Set (nine different grayshades)
On mono TV sets, Colors 0 and D-F can be used for Black/Gray/White colors as
usually, and Colors 1-C are all displayed as grayshades: 01h-0Ch=Black,
11h-1Ch=Med/Dark Gray, 21h-2Ch=Med/Light Gray, 31h-3Ch=Bright Gray. Intensity
ramp example: 0Eh, 2Dh, 11h, 00h, 21h, 01h, 3Dh, 31h, 30h. Also, the Color
Emphasis bits are somewhat affecting the luminance output, even on mono
television sets.
Monochrome Bit (three different grayshades)
When Port 2001h/Bit0 is set: The lower 4bits of all palette entries are treated
to be zero. That means that only 3 colors can be displayed: Gray, Light Gray,
and White. All other colors cannot be used (even Black and Dark Gray are
disabled). The Color Emphasis bits can be still used (eg. to change above 3
gray-shades into 3 pastelized green-shades)."