Pokémon Yellow predefined functions list

Pokemon Yellow Defined Functions

All values in hex!

Some values that are stated "Nonfunctional" may do something when certain conditions are met, but I'm lazy, so...

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00: Shows in-battle HUD for exactly 5 frames

01 - 03: Nonfunctional

04: Writes random garbage to tile graphics, gameplay unaffected

05 - 06: Nonfunctional

07: Instant Pokemon Center (no animation, but HP and PP refilled and status restored to normal)

08: Nonfunctional

09: Softlock

0A: Softlock

0B - 0C: Nonfunctional

0D - 0E: Softlock

0F: Faux New Game (all boxes and party Pokemon removed, items removed, badges removed, but no trainers or gyms reset. Curious.)

10 - 17: Nonfunctional

18: Faux New Game

19 - 1A: Nonfunctional

1B: First PKMN learns move named <insert first item in bag here>, but doesn't actually work

1C - 1E: Nonfunctional

1F: Poison screen flash, no sound effect or health decrease

20: Disables Up and Down button input, menus included. (Curious.)

21: Vertical screen shake

22 - 23: Nonfunctional

24: Horizontal screen shake

25: Softlock

26 - 28: Nonfunctional

29: Pokedex menu

2A - 2B: Nonfunctional

2C: Battle start, works

2D: Nonfunctional

2E: Some sort of squares flash on the bottom of the screen for exactly 5 frames (Needs investigation.)

2F: Trade, nonfunctional

30: Graphic for trainer battle start, nonfunctional

31: Small amounts of tile corruption, text to be specific.

32: Intro and title, then graphical errors (It's actually an overlay...? No actual reset occurs, just the graphics. It dumps control back to the player, so the map graphics get screwed up.)

33: Nonfunctional

34: Battle flashing. (No black, just flashing.)

35: Nonfunctional

36: First page of first pokemon's stats

37: Second page of first pokemon's stats

38: Functional trade

39 - 3A: Nonfunctional

3B: All tiles and sound filled with garbage

3C: Cut, working

3D: Pokedex data... of Hitmonchan.

3E: Nonfunctional

3F: Working save

40: Hangs for exactly 15 frames

41 - 45: Nonfunctional

46: Softlock

47: Nonfunctional

48: Softlock

49: Heals opponent in battle, outside of battle HUD replaced with text

4A: Hitmonchan's Nest page

4B: Nonfunctional

4C: Replaces text tiles 2, 3, 4, and 5 with "Trainer spotted you!" bubble

4D: Nonfunctional

4E: "Nickname?" for Hitmonchan

4F: Softlock

50 - 51: Nonfunctional

52: Writes black to entire screen, graphical only

53: Nonfunctional

54: "Wanna trade CLEFAIRY for MR.MIME?"

55: Enter Hall of Fame, then credits. Works, but screws up all menus.

56: Professor Oak's Rating

57: Softlock

58 - 5A: Nonfunctional

5B: First item used Strength, functional

5C - 60: Nonfunctional

61: Elevator menu

62: If you caught 0 kinds of pokemon, get item 0x00.

63 - 81: Softlock

82: Nonfunctional

83 - 8C: Softlock

8D: Small screen corruption, then softlock

8E - 8F: Softlock

90: Nonfunctional

91: Softlock

92: Text Box full of "BLUE" and whitespace

93: Screen fills with second tile of "GYM" and crash.

94: Nonfunctional

95 - 98: Softlock

99: Nonfunctional

9A - 9F: Softlock

A0: Nonfunctional

A1: Softlock

A2: "[]5 error." where [] = 25

A3 - A5: Softlock

A6: Nonfunctional

A7: Text box similar to 92 but filled with "LAPRAS" instead of "BLUE".

A8: Nonfunctional

A9: Softlock

AA: Nonfunctional

AB: Battle HUD appears, then "It's not very effective..."

AC: See 92

AD: Softlock

AE: Nonfunctional

AF: 3TRAINERPOKe that always turns into a Rhydon was caught!

B0: Text scramble, then crash

B1 - B5: Softlock

B6: Pops all text boxes

B7 - FF: Softlock