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EarthBound Beginnings/Map data
This is a sub-page of EarthBound Beginnings.
EarthBound Beginnings uses one very large map containing all areas in the game. To accomodate this within the small space available in a NES cartridge, two levels of tiling are used: the map is made of 64x64 tiles, which in turn are made of 16x16 tiles.
Main map data
| Range | Bits 0-5 | Bits 6-7 |
|---|---|---|
| 0000-1FFF | Map data | |
| 2000-2FFF | 64x64 chunks | |
| 3000-37FF | 16x16 metatiles | 64x64 chunk palettes |
| 3800-3FFF | Sector properties | |
The main part of the map data, located at 2000-1FFFF, is "organized" into eight 16kB banks, each containing data for 32 rows of the map and 4 tilesets. Bank 0 is at 0-3FFF, bank 1 is at 4000-7FFF, and so on until bank 7 which is at 1C000-1FFFF. You may have noticed that bank 0 is partially outside the range given. Bank 0 is special in that it only contains tilesets; there is unrelated data in the first half of it where the map would be.
Ranges stated hereafter in this section refer to offsets within each bank, rather than the whole file.
Format
Each part of the map corresponds to a square, and point to each other. For example, each group of 16 bytes (in the 2000-2FFF range) is called a "chunk", and if a chunk's bytes were:
01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10
The image would be shown as:
01 02 03 04 05 06 07 08 ...
Map data
The map itself is in the first half of each bank, from 0000-1FFF (except for bank 0, see above). Each byte corresponds to one 64x64 tile. Bits 0-5 determine which tile to use. Bit 6, if set, will use a tile from the second tileset instead of the first. Bit 7 is set on tiles which change based on events, of which there are only two in the whole game: one north of Merrysville for the rocks blocking the way to Union Station, and one at the very top of Mt. Itoi behind the "XX".
Unlike other types, they are not stored in larger squares. The chunks must be calculated manually and are not directly related to this data.
64x64 chunks
The composition of 64x64 tiles is at 2000-2FFF. Bits 0-6 select a 16x16 tile, and bit 7 determines whether to use the first or second tileset again. If the 64x64 tile was from the first tileset, then setting bit 7 will put in a 16x16 tile from the second tileset, and vice versa. Each 64x64 chunk is a 4x4 grid of metatiles, so 16 bytes.
64x64 chunk palettes
These are in the upper 2 bits of 3000-3FFF. Each byte determines the sub-palette for one of the 16x16 tiles that a 64x64 tile is made of.
16x16 metatiles
16x16 metatiles are at 3000-37FF, in the low 6 bits only. Each byte selects one 8x8 PPU tile. Unlike the other types, this is 4 bytes long (a 2x2 grid).
Sector properties
Properties associated with map sectors (squares, 4 tiles wide) are at 3800-3FFF, again in the low 6 bits only. Each sector has 4 bytes here; they are the palette, area, first tileset, and second tileset in that order. Map sectors with palettes differing from the current palette are not displayed.