Latest revision as of 17:11, 6 April 2020

The fix layer is a non-scrollable, tile-based layer with transparency which has the highest priority on the display (it always overlaps sprites). It is most often used to display text or HUDs like scores and health bars.

It is somewhat limited compared to sprites:

Tilesets can only contain a maximum of 4096 tiles (128KiB) without using bankswitching (see below).
Only the first 16 palettes can be used.

Graphics format

Fix tiles are 8*8 pixels, they're stored in the S ROM, or in FIX files before getting loaded to PSRAM in CD systems. In some MVS systems, there is an embedded fix tileset stored in the SFIX ROM which can be swapped with the cartridge's one.

The tiles graphics are 4BPP like sprites tiles (15 colors, index 0 is transparent), each can be individually mapped to one of the first 16 palettes (4bit palette index).

See Fix graphics format for more details.

Fix map

File:Fixlayout.png

Fix layout. The grey area is part of the display but only the area in the red rectangle should be used.

The map is in VRAM starting at address $7000. The area used for display is 40*32 = 1280 words in size, but only 40x28 tiles are drawn in NTSC mode (2 hidden lines on the top and bottom).

Most games don't use the leftmost and rightmost columns, as some CRT screens can cut them off. SNK recomends only using a centered 38x28 safe zone.

Each map entry in VRAM uses a 16 bit word:

Bit	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Def	Palette number				Tile number

Tiles are mapped from top to bottom, and left to right (see layout). The VRAM_MOD ($3C0004) register can be set to 32 if tiles need to be updated in lines. See Displaying text.

Bankswitching

Games using the NEO-CMC chips are able to use more than 4096 fix tiles by using VRAM space $7500+. See Fix bankswitching.

@@ Line 1: / Line 1: @@
-The fix layer is a non-scrollable, tile-based layer with transparency which has the highest priority on the display (it always overlaps [[sprites]]). It is used to display text or HUDs like scores and health bars.
+The fix layer is a non-scrollable, tile-based layer with transparency which has the highest priority on the display (it always overlaps [[sprites]]). It is most often used to display text or HUDs like scores and health bars.
-As only 12 bits are reserved to address fix tiles, tilesets can only contain a maximum of 4096 tiles (128KiB).
+It is somewhat limited compared to sprites:
+* Tilesets can only contain a maximum of 4096 tiles (128KiB) without using bankswitching (see below).
+* Only the first 16 palettes can be used.
-== Graphics format ==
+=Graphics format=
-Tiles used are 8*8 pixels, they're stored in the [[S ROM]]s, or in [[FIX file]]s before getting loaded to [[PSRAM]] in CD systems.
+Fix tiles are 8*8 pixels, they're stored in the [[S ROM]], or in [[FIX file]]s before getting loaded to [[PSRAM]] in CD systems.
-In MVS systems, there is an embedded fix tileset stored in the [[SFIX|SFIX ROM]] which can be swapped with the cart's one.
+In some MVS systems, there is an embedded fix tileset stored in the [[SFIX ROM]] which can be swapped with the cartridge's one.
-The tiles graphics are 4BPP (15 colors, index 0 is transparent), each can be individually mapped to the first 16 [[palettes]].
+The tiles graphics are 4BPP like sprites tiles (15 colors, index 0 is transparent), each can be individually mapped to one of the first 16 [[palettes]] (4bit palette index).
 See [[Fix graphics format]] for more details.
-== Fix map ==
+=Fix map=
 [[File:Fixlayout.png|frame|Fix layout. The grey area is part of the display but only the area in the red rectangle should be used.]]
-The map is 40x32 tiles but only 40x28 tiles are drawn to the screen in NTSC mode: Therefor, there are 2 hidden lines of tiles at the beginning and the end of the map. Some games also don't use the leftmost and rightmost columns, as some misaligned CRT screens (?) can cut them off.
+[[File:Fixlayout-tmpl.png|frame|Complete Fix layout map for reference.]]
-The base address in [[VRAM]] for the map is $7000. Each tile uses one 16bit word:
+The map is in [[VRAM]] starting at address $7000. The area used for display is 40*32 = 1280 words in size, but only 40x28 tiles are drawn in NTSC mode (2 hidden lines on the top and bottom).
+Most games don't use the leftmost and rightmost columns, as some CRT screens can cut them off. SNK recomends only using a centered 38x28 safe zone.
+Each map entry in VRAM uses a 16 bit word:
 {{16BitRegister|Palette number|4|Tile number|12}}
-Tiles are mapped from up to bottom, and left to right (see layout). The '''VRAM_MOD''' ($3C0004) register can be set to 32 if tiles need to be updated in lines. See [[Displaying text]].
+Tiles are mapped from '''top to bottom, and left to right''' (see layout). The {{Reg|VRAM_MOD ($3C0004)}} register can be set to 32 if tiles need to be updated in lines. See [[Displaying text]].
+=Bankswitching=
+Games using the [[NEO-CMC]] chips are able to use more than 4096 fix tiles by using VRAM space $7500+. See [[Fix bankswitching]].
 [[Category:Video system]]

Fix layer: Difference between revisions

Latest revision as of 17:11, 6 April 2020

Graphics format

Fix map

Bankswitching

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