[−][src]Module gba_addresses::palram

Palette RAM (PALRAM).

This holds RGB palette entries. Each entry is 16-bit, 5-bits per channel, and the highest bit is ignored. The bits are laid out as follows:

0bXBBBBBGG_GGGRRRRR

There are two palettes, one for backgrounds and one for objects.

The palettes can be used in 4bpp mode or 8bpp mode:

  • In 4bpp mode, the palette consists of 16 "palbanks", and then each palbank has 16 entries. Entry 0 of each palbank is considered transparent, so there's 15 usable entries per palbank.
  • In 8bpp mode, the palette consists of a single 256 entry block. Again, entry 0 is considered to be a transparent entry, so there's 255 usable entries.
  • Each individual background or object decides if it wants to use the palettes in 4bpp mode of 8bpp mode. You can freely intermix modes, the overall memory is the same either way.

Entry 0 of the background palette is the "backdrop" color. If no background or object would end up drawing to a particular pixel, the backdrop color is used for that pixel.

You cannot validly write a single byte to PALRAM. If you do so, the 8-bits are written to both the upper and lower 8-bits of the given 16-bit segment of memory. This isn't a big deal, since all palette entries are 16-bit values anyway.

  • Size: 1kb
  • Wait states: 0
  • Bus Size: 16-bit
  • Read/Write: 16/32

Constants

BACKDROP_COLOR_ADDR

The address of the backdrop color.

BG_PALETTE_RAM_ADDR

Base Address of the background palette.

BG_PALETTE_RAM_COUNT

There's 256 slots in the background palette.

BG_PALETTE_RAM_ENTRY_SIZE

Palette entries are 2 bytes each.

OBJ_PALETTE_RAM_ADDR

Base Address of the object palette.

OBJ_PALETTE_RAM_COUNT

There's 256 slots in the object palette.

OBJ_PALETTE_RAM_ENTRY_SIZE

Palette entries are 2 bytes each.

Functions

index_bg_palette_4bpp

Index the background palette to a 4bpp palbank and index.

index_bg_palette_8bpp

Index the background palette to a 8bpp index.

index_obj_palette_4bpp

Index the object palette to a 4bpp palbank and index.

index_obj_palette_8bpp

Index the object palette to a 8bpp index.