Pokémon Red and Blue/Notes

The following article is a Notes Page for Pokémon Red and Blue.

False 'level' addresses

These are stored values that may change after switching a Pokémon up to a specific position in the party. The value for that process is updated after depositing and withdrawing the Pokémon into a box.

Pokémon ID

The RAM structure includes references Pokémon IDs. These do not match the Pokédex number in game. Instead, they correspond to the pokedex order listed in the ROM section, but with some numbers skipped:

Pokémon	ID
Rhydon	01
Kangaskhan	02
Nidoran M	03
Clefairy	04
Spearow	05
Voltorb	06
Nidoking	07
Slowbro	08
Ivysaur	09
Exeggutor	0A
Lickitung	0B
Exeggcute	0C
Grimer	0D
Gengar	0E
Nidoran F	0F
Nidoqueen	10
Cubone	11
Rhyhorn	12
Lapras	13
Arcanine	14
Mew	15
Gyardos	16
Shellder	17
Tentacool	18
Gastly	19
Scyther	1A
Staryu	1B
Blastoise	1C
Pinsir	1D
Tangela	1E
Growlithe	21
Onix	22
Fearow	23
Pidgey	24
Slowpoke	25
Kadabra	26
Graveler	27
Chansey	28
Machoke	29
Mr. Mime	2A
Hitmonlee	2B
Hitmonchan	2C
Arbok	2D
Parasect	2E
Psyduck	2F
Drowzee	30
Golem	31
Magmar	33
Electabuzz	35
Magneton	36
Koffing	37
Mankey	39
Seel	3A
Diglett	3B
Tauros	3C
Farfetch	40
Venonat	41
Dragonite	42
Doduo	46
Poliwag	47
Jynx	48
Moltres	49
Articuno	4A
Zapdos	4B
Ditto	4C
Meowth	4D
Krabby	4E
Vulpix	52
Ninetales	53
Pikachu	54
Raichu	55
Dratini	58
Dragonair	59
Kabuto	5A
Kabutops	5B
Horsea	5C
Seadra	5D
Sandshrew	60
Sandslash	61
Omanyte	62
Omastar	63
Jigglypuff	64
Wigglytuff	65
Eevee	66
Flareon	67
Jolteon	68
Vaporeon	69
Machop	6A
Zubat	6B
Ekans	6C
Paras	6D
Poliwhirl	6E
Poliwrath	6F
Weedle	70
Kakuna	71
Beedrill	72
Dodrio	74
Primeape	75
Dugtrio	76
Venomoth	77
Dewgong	78
Caterpie	7B
Metapod	7C
Butterfree	7D
Machamp	7E
Golduck	80
Hypno	81
Golbat	82
Mewtwo	83
Snorlax	84
Magikarp	85
Muk	88
Kingler	8A
Cloyster	8B
Electrode	8D
Clefable	8E
Weezing	8F
Persian	90
Marowak	91
Haunter	93
Abra	94
Alakazam	95
Pidgeotto	96
Pidgeot	97
Starmie	98
Bulbasaur	99
Venusaur	9A
Tentacruel	9B
Goldeen	9D
Seaking	9E
Ponyta	A3
Rapidash	A4
Rattata	A5
Raticate	A6
Nidorino	A7
Nidorina	A8
Geodude	A9
Porygon	AA
Aerodactyl	AB
Magnemite	AD
Charmander	B0
Squirtle	B1
Charmeleon	B2
Wartortle	B3
Charizard	B4
Oddish	B9
Gloom	BA
Vileplume	BB
Bellsprout	BC
Weepinbell	BD
Victreebel	BE

Tileset headers

12 bytes per header, as follows :

1 byte  - Bank ID of blocks and tiles
2 bytes - Pointer to blocks
2 bytes - Pointer to tiles
2 bytes - Pointer to collision data
3 bytes - Up to 3 'talking-over tiles' tile numbers ("empty" slots are filled with $FF)
1 byte  - Grass tile ($FF if none)
1 byte  - Animation flag

Since the player moves on a 2x2 tile grid, the game checks the bottom-left tile of such a group for its properties (grass, talking-over...)

(Note : there's an inconsistency with this, the game uses the bottom-right tile to determine water, hence the Old Man Glitch)

Blocks

Maps are made up of 4x4 tile blocks, stored (how?)

A tile is 8x8 pixels, so a block is 32x32 pixels.

Tiles

Tiles are stored using the GB's format, and directly copied to VRAM.

Collision data

This is a pointer to a list of tile numbers over which the player can walk. Terminated with a FF byte.

Talking-over tiles

These are tiles which allow the player to talk to a person on the other side, such as the counters in the Pokémon Centers or Pokémarts.

Each tileset can have up to 3 talking over tiles. Use FF to fill the unused slots.

Grass tile

This is both a tile that will be rendered above sprites, and one where random "grass" encounters are possible.

Animation flag

This byte defines whether the tileset has animated tiles.

If the byte is zero, no animations take place. Otherwise, the water animation will be in effect, and if bit 0 is reset, the flower animation also will.

The water animation is done by rotating tile $14's pixels left and right. The flower animation, however, overwrites tile $03 with images stored in the ROM, at addresses $1F29, $1F29 and $1F39.

Map headers

This contains all the data (pointers count as data) to build the map.

1 byte  - Tileset ID
1 byte  - (Y Size) Map height
1 byte  - (X Size) Map width
2 bytes - Pointer to map data
2 bytes - Pointer to text pointers
2 bytes - Pointer to script
1 byte  - Connection Byte
11 bytes per connection - Connection data (No connections? Straight to object data!)
2 bytes - Pointer to object data

Tileset numbers

The tileset descriptions are copied from a document compiled by Cartmic, called "Pokémon Red Documents", which may help you with other stuff too.

Tileset No.	Location in US R/B ROM	Description
00	C7BE	Outside
01	C7CA	Red's House
02	C7D6	Pokémon Center
03	C7E2	Viridian Forest
04	C7EE	Red's House (copy)
05	C7FA	Gym
06	C806	Pokémon Center
07	C812	Gym (copy)
08	C81E	House
09	C82A	Museum
0A	C836	Museum (copy)
0B	C842	Underground Path
0C	C84E	Museum (second copy)
0D	C85A	S.S. Anne
0E	C866	Vermilion Port
0F	C872	Pokémon Cemetery
10	C87E	Silph Co.
11	C88A	Cave
12	C896	Celadon Mart
13	C8A2	Game Freak HQ
14	C8AE	Lab
15	C8BA	Bike Shop/Cable Center
16	C8C6	Cinnabar Mansion/Power Plant etc
17	C8D2	Indigo Plateau

NOTE: As you can see there's multiple copies of some tileset headers. They are literally copies.

If you're ROM hacking the game and want to add custom tilesets, you can delete copies to make room. However make sure that all maps that used the copy now use the original.

Map height (Y axis) & width (X axis)

Exactly that, the amount of blocks high and wide the map data is.

Map data pointer

You can use the GoldMap engine for hacking map data quite easily.

The map you walk around on and stuff is stored as block indexes. A single block consists of 4x4 tiles.

Pointer to text pointers

This points to a list of pointers. When the game attempts to display textbox #3, it will fetch the 3rd pointer in this list.

(Note : textbox #0 is hardwired to the START menu)

Pointer to script

Points to a function ran on each frame spent in this overworld (for example, not ran while a textbox is active)

If a map has a functionality you can't implement otherwise, check this out. You can sometimes find things like XY positions of Poké Balls and 1-time only Pokémon.

Connection mask

Note: If this value is $00 it is immediately followed by the object data pointer, no gap.

Connections can be obtained with binary masks:

connect_byte & (1 << 3) -> North
connect_byte & (1 << 2) -> South
connect_byte & (1 << 1) -> West
connect_byte & (1 << 0) -> East

List of values:

00 = No Connections
01 = East
02 = West
03 = West + East
04 = South
05 = South + East
06 = South + West
07 = South + West + East
08 = North
09 = North + East
0A = North + West
0B = North + West + East
0C = North + South
0D = North + South + East
0E = North + South + West
0F = North + South + West + East

Connection Data

Size can range from 0 to 44 bytes.

Probably the toughest thing to manipulate. This will certainly require planning, with no background distractions. (Unless an editor gets built that can hack the connections for RGBY.)

X/Y movement of connection

A X movement is how many map blocks there are to the left of one of your north/south connections.

A Y movement is how many map blocks there are above your west/east connection.

Structure

1 byte  - Map ID of connected map
2 bytes - Pointer to "connection strip"s upper-left block (Connected map)
2 bytes - Pointer to "connection strip"s upper-left block (Current map)
1 byte  - "Bigness"
1 byte  - Map Width
1 byte  - Y alignment
1 byte  - X alignment
2 bytes - Window

TODO : convert this block to wiki format.

===============================================================================
    #1 : Map Indexes
===============================================================================

Not included! Download UltraMap, the text file known as "RedEnglish.ini"
contains all the Map Indexes in decimal for R/B, which you'll obviously need
to convert to hex.

===============================================================================
 #2-#3 : "Connection Strip" Location
===============================================================================

The "connection strip" pointer -- points to the area of the connected map that
is visible when standing before you even enter it. Points to the upperleft
block of the "connection strip".
      * connection strip is always 3 blocks wide (E/W connection)
                                   3 blocks high (N/S connection)

===============================================================================
 #4-#5 : Current Map Position
===============================================================================

This points to the part of the current map (further up in RAM)
that the connection strips upperleft block is placed on the current map.

____________________
Connection |
Direction  | Formula
___________|_______

     North: C6EB + X_Movement_of_Connection Strip

     South: C6EB + (Height of Map + 3) * (Width of Map + 6) +
                   X_Movement_of_Connection Strip

      West: C6E8 + (Width of Map + 6) * (Y_Movement_of_"Connection Strip" + 3)

      East: C6E5 + (Width of Map + 6) * (Y_Movement_of_"Connection Strip" + 4)

===============================================================================
    #6 : Map "Bigness"
===============================================================================

North/South Connection = Connected Maps Width
East/West Connection = Connected Maps Height

===============================================================================
    #7 : Map Width
===============================================================================

The width of the connected map.

===============================================================================
    #8 : Y alignment
===============================================================================

Relative Y-position of player after entering connected map.

____________________
Connection |
Direction  | Formula
___________|_______
     North: (Height_of_connected_map * 2) - 1
     South: 0
 West/East: (Y_movement_of_connection_strip_in_blocks * -2)

===============================================================================
    #9 : X alignment
===============================================================================

Relative X-Position of player after entering connected map.

____________________
Connection |
Direction  | Formula
___________|_______
North/South: (X_movement_of_connection_strip_in_blocks * -2)
       West: (Width_of_connected_map * 2) - 1
       East: 0

===============================================================================
#10-#11 : Window
===============================================================================

Position of the upper left block after entering the Map.

____________________
Connection |
Direction  | Formula
___________|_______
     Above: C6E9h + Height_of_connected_map * (Width_of_connected_map + 6)
South/East: C6EFh + Width_of_connected_map
      West: C6EEh + 2 * Width_of_connected_map
...............................................................................

Example

PKMN Red Example -- Saffron City (Header: 0x509A4) Diagram:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Saffrons need-to-know stats:

Block Height (Y): 12
 Block Width (X): 14
 Connection Byte: 0F (North + South + West + East)
                      -       -       -      -
 + = current maps border blocks

++++++++NNNNNNNNNN++++++++
++++++++NNNNNNNNNN++++++++
++++++++NNNNNNNNNN++++++++
+++####################+++
+++####################+++
+++####### My #########+++
+++####################+++
WWW####### Name's #####EEE
WWW####################EEE
WWW###### Saffron #####EEE
WWW####################EEE
WWW###### City! #######EEE
WWW####################EEE
WWW####################EEE
WWW####################EEE
WWW####################EEE
+++####################+++
+++####################+++
+++####################+++
+++####################+++
+++####################+++
++++++++SSSSSSSSSS++++++++
++++++++SSSSSSSSSS++++++++
++++++++SSSSSSSSSS++++++++

Connection to Route 5 (to the North)
              *Y: 12
              *X: 0A
              *X_Movement_of_Connection Strip = 5
       Map Index: 10
Connection Strip: 4668
 Where Connected: C6F0 (C6EB + 5)
       "Bigness": 0A
           Width: 0A
     Y alignment: 23 (12 * 2 - 1)
     X alignment: F6 (5 * -2)
          Window: C809 (C6E9 + (12 * (0A + 6)))

Connection to Route 6 (to the South)
              *Y: 12
              *X: 0A
              *X_Movement_of_Connection Strip = 5
       Map Index: 11
Connection Strip: 4079
 Where Connected: C912 (C6EB + ((12 + 3) * (14 + 6)) + 5)
       "Bigness": 0A
           Width: 0A
     Y alignment: 00
     X alignment: F6 (5 * -2)
          Window: C6F9 (C6EF + 0A)

Connection to Route 7 (to the West)
              *Y: 09
              *X: 0A
              *Y_Movement_of_Connection Strip = 4
       Map Index: 12
Connection Strip: 4058
 Where Connected: C79E (C6E8 + (14 + 6) * (4 + 3))
       "Bigness": 09
           Width: 0A
     Y alignment: F8 (4 * -2)
     X alignment: 13 ((0A * 2) - 1)
          Window: C702 (C6EE + (0A * 2))

Connection to Route 8 (to the East)
              *Y: 09
              *X: 1E
              *Y_Movement_of_Connection Strip = 4
       Map Index: 13
Connection Strip: 41C6
 Where Connected: C7B5 (C6E5 + (14 + 6) * (4 + 4))
       "Bigness": 09
           Width: 1E
     Y alignment: F8 (4 * -2)
     X alignment: 00
          Window: C70D (C6EF + 1E)

Object Data

1 byte  - Border block ID
1 byte  - Number of warps
4 bytes per warp - Warp data
1 byte  - Number of signs
3 bytes per sign - Sign data
1 byte  - Number of NPCs (total)
6/8/7 bytes per NPC - NPC data
4 bytes per warp-to - Warp-To data

Warps

1 byte  - Y position
1 byte  - X position
1 byte  - Destination warp-to's ID (within target map)
1 byte  - Destination map

Signposts

1 byte  - Y position
1 byte  - X position
1 byte  - Text string ID

NPCs

In order to distinguish People, Trainers and Items, you must check the text string ID:

strID & (1 << 6) != 0 : Trainer (2 extra bytes, the trainer class and roster IDs)

strID & (1 << 7) != 0 -> Item (1 extra byte, the item ID)

Normal people

1 byte  - Picture number
1 byte  - Y position + 4
1 byte  - X position + 4
1 byte  - Movement byte 1
1 byte  - Movement byte 2
1 byte  - Text string ID

Trainers / One-time Pokémon

One-time Pokémon and Trainers are essentially the same thing, separated by their species ID. If it's under 200, it's a Pokémon. Over or equal to 200, it's a Trainer.

1 byte  - Picture number
1 byte  - Y position + 4
1 byte  - X position + 4
1 byte  - Movement 1
1 byte  - Movement 2
1 byte  - Text string ID
1 byte  - Pokémon species ID / Trainer class
1 byte  - Pokemon level / Trainer's roster ID

Items

1 byte  - Picture number
1 byte  - Y position + 4
1 byte  - X position + 4
1 byte  - Movement 1
1 byte  - Movement 2
1 byte  - Text string ID
1 byte  - Item ID

Warp-To Points

2 bytes - Event Displacement
1 byte  - Y position
1 byte  - X position

Sprites

Sprites are loaded when changing maps. However, there is a little subtlety : when traversing a map connection, the game assumes the correct sprite set is loaded, and doesn't reload sprites. (Hence glitchy sprites sometimes observed with Walk Through Walls).

The other occasion where sprites are loaded is when a text display is closed ; the game reloads sprites because the "walking" sprites are overwritten by font tiles.

Also, if there are no sprites (NPCs) the game doesn't reload sprite graphics.

How the game reloads sprites differs for "exterior" and "interior" maps.

Exterior maps

The game reads an entry from the table at 17A64, MapSpriteSets. If the entry is < $F0, the game uses the corresponding sprite set. Otherwise, it uses the corresponding split sprite set (see dedicated section).

Split sprite sets

Some exterior maps have two sprite sets, which depend on position.

Consider the entry read from MapSpriteSets. If the entry is $F8, that's Route 20 - a special case with a complex splitting. See its dedicated section.

The table maintains a table at 17A89, SplitMapSpriteSets, structured like so :

1 byte  - Split type (1 = East/West division, 2 = North/South division)
1 byte  - Split coordinate
1 byte  - Sprite set ID if coordinate <  split coordinate
1 byte  - Sprite set ID if coordinate >= split coordinate

The game reads an entry, indexed using (the byte read from MapSpriteSets AND $0F), and uses this sprite set.

Sea Route 20

Sea Route 20 has two sprite sets, $01 (West) and $0A (East). The only thing that differs from above is that the splitting is more complex.

If X coordinate < $2B
  Use set $01
End

If X coordinate >= $3E
  Use set $0A
End

If X coordinate >= $37
  If Y coordinate < $08
    Use set $0A
  Else
    Use set $01
  End
Else
  If Y coordinate < $0D
    Use set $0A
  Else
    Use set $01
  End
End

More visually :

Y X  ... 28 29 2A 2B 2C 2D ... 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F 40 ...

.    ... .  .  .  .  .  .  ... .  .  .  .  .  .  .  .  .  .  .  .  .  ...
.    ... .  .  .  .  .  .  ... .  .  .  .  .  .  .  .  .  .  .  .  .  ...
.    ... .  .  .  .  .  .  ... .  .  .  .  .  .  .  .  .  .  .  .  .  ...
05   ... 01 01 01 0A 0A 0A ... 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A ...
06   ... 01 01 01 0A 0A 0A ... 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A ...
07   ... 01 01 01 0A 0A 0A ... 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A 0A ...
08   ... 01 01 01 0A 0A 0A ... 0A 0A 0A 01 01 01 01 01 01 01 0A 0A 0A ...
09   ... 01 01 01 0A 0A 0A ... 0A 0A 0A 01 01 01 01 01 01 01 0A 0A 0A ...
0A   ... 01 01 01 0A 0A 0A ... 0A 0A 0A 01 01 01 01 01 01 01 0A 0A 0A ...
0B   ... 01 01 01 0A 0A 0A ... 0A 0A 0A 01 01 01 01 01 01 01 0A 0A 0A ...
0C   ... 01 01 01 0A 0A 0A ... 0A 0A 0A 01 01 01 01 01 01 01 0A 0A 0A ...
0D   ... 01 01 01 01 01 01 ... 01 01 01 01 01 01 01 01 01 01 0A 0A 0A ...
0E   ... 01 01 01 01 01 01 ... 01 01 01 01 01 01 01 01 01 01 0A 0A 0A ...
0F   ... 01 01 01 01 01 01 ... 01 01 01 01 01 01 01 01 01 01 0A 0A 0A ...
.    ... .  .  .  .  .  .  ... .  .  .  .  .  .  .  .  .  .  .  .  .  ...
.    ... .  .  .  .  .  .  ... .  .  .  .  .  .  .  .  .  .  .  .  .  ...
.    ... .  .  .  .  .  .  ... .  .  .  .  .  .  .  .  .  .  .  .  .  ...

Interior maps

The game loads sprites by request, ie. the sprite tiles will be loaded as required by NPCs present on the loaded map.

Useful notes

Picture numbers

In order to get the ROM address of the tile relative to an entity (people/trainers/items), here is the formula to focus on the entity information:

 5 * $4000 + ($7b27 + 4 * (picture_id - 1)) % $4000

Then the entity information is stored according to this:

2 bytes - Tile address
1 byte  - Total size of tile data
1 byte  - Bank ID

So then, address = bankID * 0x4000 + tileAddr % 0x4000

Event displacement formula

$C6EF + (Map width) + (Map width + 6) * (Y offset) + (X offset)

Pointers

R/B Pointers to Map Headers: 0x01AE R/B Map Header Banks: 0xC23D R/B Pointer to Tileset Headers: 0xC767

Misc.

Maximum tileset size in VRAM: 6 rows of 16 tiles (9000-95FF)

Credits

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    RGBY Map Headers & Stuff That Goes With It
    Version 1.6
    -Feel free to distribute this document and/or edit it.
    -Try and credit people you get info from and/or write how you updated.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Things that need adding:
------------------------
More information about tilesets, and info about what sprites get loaded for
which maps.

Updates:
--------
v1.6 by ISSOtm: Re-formatted the document, less ASCII and more wiki.
v1.5.1 by Sawakita: Fixed Tileset Header, completely (including last byte: Animation Flag)
v1.5 by phire: Completed Tileset Header, except for that last byte.
v1.4 Complete object data info with details about picture id.
v1.3 Edit by Cartmic to include almost completed tileset header information
     and Hat's further clarification on what the X/Y Movement of the Connection means.
v1.2: By ubitux: Add some information about connections and distinction between entities (People/Trainers/Items)
v1.11: Typo fixed by Hat: "01 = North" changed to "01 = East". Thanks to IIMarckus for pointing that out.
v1.1: By Hat, minor improvements.
v1.0: Original version typed up by Hat.

Main Credits (Structure Information):
-------------------------------------
  [Xeon]
    Wrote some stuff about Map Headers and Object Data.
    Which this document expands upon, a bit.

  [F-Zero] & [Tauwasser]
    Wrote a document (in German) explaining how GSC connection data is stored.
    RGBY connection data is stored almost the same way, it turns out, so
    that helped a great deal. All that is really different is the values you
    add the amount of blocks to.
...............................................................................