View source for Palettes

The SNES has a palette of 256 colors, stored as 256 15-bit words in '''CGRAM'''.

A SNES color entry gives an RGB color with 5-bit precision in each component.

== CGRAM access ==

# Write a byte to [[PPU registers#CGADD|CGADD]] ($2121) to select one of the 256 entries in CGRAM.
# Write two bytes to [[PPU registers#CGDATA|CGDATA]] ($2121) to set the 15-bit RGB color for that entry. (Low byte first.)

     CGDATA ($2122)
 15  bit  8   7  bit  0
  ---- ----   ---- ----
  .BBB BBGG   GGGR RRRR
   ||| ||||   |||| ||||
   ||| ||||   |||+-++++- Red component 
   ||| ||++---+++------- Green component
   +++-++-------------- Blue component

After two writes to CGDATA, CGADD will automatically be incremented to the next entry.

Entries can also be read back through [[PPU registers#CGDATAREAD|CGDATAREAD]] ($213B). Note that because the high bit is unused, it returns an unreliable value that should be ignored.

== Assignment ==

* CGRAM entry 0 is always used as the background color, beneath all the [[background]] layers and [[sprites]], or where all other rendering is disabled or windowed.
* [[Tiles#2bpp|2bpp]] tiles use groups of 4 from CGRAM. The first of 4 will be unseen, as a tile pixel of 0 is always transparent, but the remaining 3 will be used to color the visible tile.
* [[Tiles#4bpp|4bpp]] tiles use groups of 16. Again the first entry is always transparent and unseen. [[Backgrounds]] use the first 8 groups of 16 (0-127) and [[sprites]] use the last 8 groups (128-255).
* [[Tiles#8bpp|8bpp]] tiles can use the entire contents of CGRAM, except entry 0 which is always transparent. This also includes [[mode 7]] tiles.
* [[Direct color]] tiles do not use the CGRAM palette at all, instead specifying an 8-bit color directly with their bits.

== See Also ==
* [[Tiles]]
* [[Backgrounds]]
* [[Sprites]]

== References ==
* [[SNES Development Manual]] - Book I A-17 CG-RAM