PPU registers
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Display configuration
INIDISP - Screen display ($2100 write)
7 bit 0 ---- ---- F... BBBB | |||| | ++++- Screen brightness (linear steps from 0 = none to $F = full) +--------- Force blanking
BGMODE - BG mode and Character size ($2105 write)
7 bit 0 ---- ---- 4321 PMMM |||| |||| |||| |+++- BG mode |||| +---- Mode 1 BG3 priority (0 = normal, 1 = high) |||+------ BG1 character size (0 = 8x8, 1 = 16x16) ||+------- BG2 character size (0 = 8x8, 1 = 16x16) |+-------- BG3 character size (0 = 8x8, 1 = 16x16) +--------- BG4 character size (0 = 8x8, 1 = 16x16)
Mode| BG bit depth |Offsets | Priorities (front -> back) | Notes
|BG1 BG2 BG3 BG4|per tile| |
0 | 2 2 2 2 | No | S3 1H 2H S2 1L 2L S1 3H 4H S0 3L 4L|
1 | 4 4 2 | No | S3 1H 2H S2 1L 2L S1 3H S0 3L |BG3 priority = 0
| | |3H S3 1H 2H S2 1L 2L S1 S0 3L |BG3 priority = 1
2 | 4 4 | Yes | S3 1H S2 2H S1 1L S0 2L |
3 | 8 4 | No | S3 1H S2 2H S1 1L S0 2L |
4 | 8 2 | Yes | S3 1H S2 2H S1 1L S0 2L |
5 | 4 2 | No | S3 1H S2 2H S1 1L S0 2L |Fixed 16 pixel char width. Forced high-res mode.
6 | 4 | Yes | S3 1H S2 S1 1L S0 |Fixed 16 pixel char width. Forced high-res mode.
7 | 8 | No | S3 S2 S1 1L S0 |Fixed 8x8 char size.
7EXT| 8 7 | No | S3 S2 2H S1 1L S0 2L |Fixed 8x8 char size. BG2 bit 7 acts as priority.
MOSAIC - Screen pixelation ($2106 write)
7 bit 0 ---- ---- SSSS 4321 |||| |||| |||| |||+- Enable BG1 mosaic |||| ||+-- Enable BG2 mosaic |||| |+--- Enable BG3 mosaic |||| +---- Enable BG4 mosaic ++++------ Mosaic size in pixels (0 = 1x1, ..., 15 = 16x16)
BGxSC - BG1-4 tilemap address and size ($2107-$210A write)
7 bit 0 ---- ---- AAAA AAYX |||| |||| |||| |||+- Horizontal tilemap count (0 = 1 tilemap, 1 = 2 tilemaps) |||| ||+-- Vertical tilemap count (0 = 1 tilemap, 1 = 2 tilemaps) ++++-++--- Tilemap VRAM address (address = AAAAAA << 10)
CHR word base address
BG12NBA - BG1 and BG2 CHR word base address ($210B write)
7 bit 0 ---- ---- BBBB AAAA |||| |||| |||| ++++- BG1 CHR word base address (address = AAAA << 12) ++++------ BG2 CHR word base address (address = BBBB << 12)
BG34NBA - BG3 and BG4 CHR word base address ($210C write)
7 bit 0 ---- ---- DDDD CCCC |||| |||| |||| ++++- BG3 CHR word base address (address = CCCC << 12) ++++------ BG4 CHR word base address (address = DDDD << 12)
Layer enable
TM - Main screen layer enable ($212C write)
7 bit 0 ---- ---- ...O 4321 | |||| | |||+- Enable BG1 on main screen | ||+-- Enable BG2 on main screen | |+--- Enable BG3 on main screen | +---- Enable BG4 on main screen +------ Enable OBJ on main screen
TS - Subscreen layer enable ($212D write)
7 bit 0 ---- ---- ...O 4321 | |||| | |||+- Enable BG1 on subscreen | ||+-- Enable BG2 on subscreen | |+--- Enable BG3 on subscreen | +---- Enable BG4 on subscreen +------ Enable OBJ on subscreen
SETINI - Screen Mode/Video Select ($2133 write)
7 bit 0 ---- ---- EX.. HOiI || |||| || |||+- Screen interlacing || ||+-- OBJ interlacing || |+--- Overscan mode || +---- High-res mode |+-------- EXTBG mode +--------- External sync
Windows
Window mask settings
W12SEL - Window Mask Settings for BG1 and BG2 ($2123 write)
7 bit 0 ---- ---- DdCc BbAa |||| |||| |||| |||+- Invert window 1 for BG1 |||| ||+-- Enable window 1 for BG1 |||| |+--- Invert window 2 for BG1 |||| +---- Enable window 2 for BG1 |||+------ Invert window 1 for BG2 ||+------- Enable window 1 for BG2 |+-------- Invert window 2 for BG2 +--------- Enable window 2 for BG2
W34SEL - Window Mask Settings for BG3 and BG4 ($2124 write)
7 bit 0 ---- ---- HhGg FfEe |||| |||| |||| |||+- Invert window 1 for BG3 |||| ||+-- Enable window 1 for BG3 |||| |+--- Invert window 2 for BG3 |||| +---- Enable window 2 for BG3 |||+------ Invert window 1 for BG4 ||+------- Enable window 1 for BG4 |+-------- Invert window 2 for BG4 +--------- Enable window 2 for BG4
WOBJSEL - Window Mask Settings for OBJ and Color Window ($2125 write)
7 bit 0 ---- ---- LlKk JjIi |||| |||| |||| |||+- Invert window 1 for OBJ |||| ||+-- Enable window 1 for OBJ |||| |+--- Invert window 2 for OBJ |||| +---- Enable window 2 for OBJ |||+------ Invert window 1 for color math ||+------- Enable window 1 for color math |+-------- Invert window 2 for color math +--------- Enable window 2 for color math
Window positions
WH0 - Window 1 left position ($2126 write)
7 bit 0 ---- ---- LLLL LLLL |||| |||| ++++-++++- Window 1 left edge position
WH1 - Window 1 right position ($2127 write)
7 bit 0 ---- ---- RRRR RRRR |||| |||| ++++-++++- Window 1 right edge position
WH2 - Window 2 left position ($2128 write)
7 bit 0 ---- ---- LLLL LLLL |||| |||| ++++-++++- Window 2 left edge position
WH3 - Window 2 right position ($2129 write)
7 bit 0 ---- ---- RRRR RRRR |||| |||| ++++-++++- Window 2 left edge position
Window mask logic
WBGLOG - Window BG mask logic ($212A write)
7 bit 0 ---- ---- 4433 2211 |||| |||| |||| ||++- BG1 window mask logic |||| ++--- BG2 window mask logic ||++------ BG3 window mask logic ++-------- BG4 window mask logic
WOBJLOG - Window OBJ and color math mask logic ($212B write)
7 bit 0
---- ----
.... CCOO
||||
||++- OBJ window mask logic
++--- Color window mask logic
Mask logic types Value|Logic 00 | OR 01 | AND 10 | XOR 11 | XNOR
Window enable
TMW - Main screen layer window enable ($212E write)
7 bit 0 ---- ---- ...O 4321 | |||| | |||+- Apply enabled windows to main screen BG1 | ||+-- Apply enabled windows to main screen BG2 | |+--- Apply enabled windows to main screen BG3 | +---- Apply enabled windows to main screen BG4 +------ Apply enabled windows to main screen OBJ
TSW - Subscreen layer window enable ($212F write)
7 bit 0 ---- ---- ...O 4321 | |||| | |||+- Apply enabled windows to subscreen BG1 | ||+-- Apply enabled windows to subscreen BG2 | |+--- Apply enabled windows to subscreen BG3 | +---- Apply enabled windows to subscreen BG4 +------ Apply enabled windows to subscreen OBJ
Color math
CGWSEL - Color addition select ($2130 write)
7 bit 0 ---- ---- BBMM ..AD |||| || |||| |+- Direct color mode |||| +-- Addend (0 = fixed color, 1 = subscreen) ||++------ Color math disable region ++-------- Clip colors to black before math region
Region types Value|Region 00 |Nowhere 01 |Outside color window 10 |Inside color window 11 |Everywhere
CGADSUB - Color math designation ($2131 write)
7 bit 0 ---- ---- MHBO 4321 |||| |||| |||| |||+- BG1 color math enable |||| ||+-- BG2 color math enable |||| |+--- BG3 color math enable |||| +---- BG4 color math enable |||+------ OBJ color math enable ||+------- Backdrop color math enable |+-------- Half color math +--------- Operator type (0 = add, 1 = subtract)
COLDATA - Fixed color data ($2131 write)
7 bit 0 ---- ---- BGRC CCCC |||| |||| |||+-++++- Color value ||+------- Write color value to blue channel |+-------- Write color value to green channel +--------- Write color value to red channel
