My Brill Game Site My Brill Game Site

Toejam and Earl

ROM File: Toejam & Earl (REV 00) (U) [!].bin

The disassembled source code to Toejam and Earl on the Sega Megadrive, my favourite game on my favourite console.

Warning! - I'm constantly working on this game so some info may not be perfectly accurate, it is constantly being refined!

This project has its own public BitBucket repository where you can view (and download) the latest copy of the source code and see up to the minutes comments and updates.

Current State (Last updated - 01 July 2019)

This project is progressing on in leaps and bounds!

If you check the repo, linked above, you'll see there is now a file called GameConstants.X68 which contains all the known RAM addresses and is filling out nicely. Some of the in game graphics are also in their own .bin files now which can be opened and edited in an application called Retro Graphics Toolkit (I know where more are but separating them out hasn't been a key focus to date).

There is information on VBlanks and HBlanks, and even a little explanation on how the game sometimes skips these! Input reading is in there, starting presents and stats are figured out as well and there is even some example code on how to overwrite these.

Even better than overwiting existing code is the example of how to extend the ROM to contain and use your own code!

I still have my dedicated topic over at RHDN that gives a play by play blow on the development so far and can also be used for comments, questions and suggestions. In conjunction with that I've also started using the Wiki on BitBucket to give more details on discoveries so far and future plans.

The high level next steps are still the same they were previously, in roughly this order:

  • Presents related data (how do Rocket Skates work, what sets how long tomatoes last, etc).
  • Random map generation routine.
  • Enemy related data (A.I., sprites, attributes like health, speed, damage, etc)
  • Player (Toejam and Earl) related data (Health, speed, sprites, etc)
  • Everything else...

There is one more thing worth mentioning in this update, I've found some friends! A group of very talented Toejam and Earl speedrunners have been kind enough to welcome me into their Discord group and share their knowledge of the game with me!

HoodyTwoShoes, MyTwoDogs and a fellow ROM Hacker and speedrunner known as Slab (who even started his own disassembly of T&E, believing mine to be abandoned!) have all happily answered any question on the game and even been there to just shoot the breeze when I need a break from coding but don't want to stop thinking about the game.

You can check out their Twitch channels here: HoodyTwoShoes, MyTwoDogs, Slab.

If there is anything you have a particular interest in let me know either on the comments here or on the RHDN topic and I'll see what I can find.

ROM (1MB, approx 4.62% deciphered as at 11-Apr-2019):
Key: Game Dynamics Data Block Graphics General Routine Error Handling ROM Header Empty Space
+/- Offset Length (hex) Opcode / Hexcode Instruction / ASCII Description
+
00000-001FF
200
00FF 8000 0000 ...
.ÿ€.....
Standard rom header with the following details:
    Initial stack pointer value: 00FF 8000
    Entry Point: 0000 0202
    ROM Details: SEGA GENESIS    (C)SEGA 1991.JULTOEJAM & EARL TOEJAM & EARL GM MK-1020 -00
+
00200-00201
2
60FE
BRA       $00000200
1 line infinite loop, used for exceptions.
+
00202-0028F
8E
4AB9 00A10008 ...
TST.L     $00A10008 ...
Megadrive initialisation routine...
+
00290-002FB
6C
8000 3FFF 0100 ...
N/A
Setup values
+
002FC-00305
A
4A79 00C00004 ...
TST.W     $00C00004 ...
Game Entry Point.
+
00306-00321
1C
4E71 ...
NOP ...
Clear RAM Routine.
+
0BB78-0BC27
AB
207C 00FFA248 ...
MOVE.L    #$00FFA248,A0 ...
Sets Toejam and Earl's Starting Stats...
+
2C52C-2E72B
21FF
N/A
N/A
Graphics
+
FFDE7-FFFFF
219
FFFF FFFF FFFF ...
N/A
Empty space

RAM (64KB, approx 1.00% deciphered as at 11-Apr-2019):
Key: Game Dynamics General Routine Unused
Offset GENS Savestate Offset Length (hex) Original Value Useful Values Description
A248 C6C0 1 03 00-09 Toejam's lives.
A249 C6C1 1 03 00-09 Earl's lives.
A24A C6C2 1 Unknown 00-?? Toejam's cash.
A24B C6C3 1 Unknown 00-?? Earl's cash.
A24C-A24D C6C4-C6C5 2 0000 0000-???? Toejam's score.
A24E-A24F C6C6-C6C7 2 0000 0000-???? Earl's score.
A250 C6C8 1 00 00-09 Toejam's promotion level. (See note 1)
A251 C6C9 1 00 00-09 Earl's promotion level. (See note 1)
A298-A29B C710-C713 4 Unknown ??-?? Toejam's health.
A29C-A29F C714-C717 4 Unknown ??-?? Earl's health.
DA8A-DAC1 FF02-FF39 37 00 00-01 Stores whether presents are identified or not. (See note 3)
DAC2-DAE1 FF3A-FF59 1F 1B or FF 00-1B Stores Toejam and Earl's inventory. (See note 2)
DAE2-DAF1 FF5A-FF69 10 Mixed Unknown Present 1 data.

ADDITIONAL INFO:
Offset GENS Savestate Offset Length (hex) Original Value Useful Values Description
CRAM Maybe? (TBC) A622-A9FD 3DD Mixed Unknown Contains the level layout of the current level.
CRAM Maybe? (TBC) A9FE-ADD9 3DC Mixed Unknown Contains the level layout of level 1.
CRAM Maybe? (TBC) ADDA-B1B5 3DD Mixed Unknown Contains the level layout of level 2 while your on level 3.
CRAM Maybe? (TBC) B800-C6BF EBF Mixed Unknown Moving letter graphics.

Notes:

Note 1:

00 = Wiener 05 = Bro
01 = Dufus 06 = Homey
02 = Poindexter 07 = Rapmaster
03 = Peanut 08 = Funk Lord
04 = Dude 09 = Goner

Note 2:

00 = Icarus Wings 0A = Rootbeer 14= Extra Buck
01 = Spring Shoes 0B = Promotion 15 = Jackpot
02 = Innertube 0C = Un-fall (Togetherness in 2 player) 16 = Tomato Rain
03 = Tomatoes 0D = Rain Cloud 17 = Earthling
04 = Sling Shot 0E = Fudge Sundae 18 = School Book
05 = Rocket Skates 0F = Decoy 19 = BoomBox
06 = Rose Bushes 10 = Total Bummer 1A = Random
07 = Super Hitops 11 = Extra Life 1B = Bonus Hi Tops
08 = Doorway 12 = Randomizer FF = Empty
09 = Food 13 = Telephone  

Note 3:

These come it pairs with the value in the even offsets representing the present and the value in the following odd offset representing if it is identified or not. 00 means it's not, 01 means it is.

History

Back in October 2015 I was contacted by a fellow Toejam and Earl fan going by the name of Juan Perez. Juan had created what he believed to be a disassembly of Toejam and Earl by running the original ROM file through a program called Disasm.exe (which I beleive is part of Sega-asm.zip). The disassembly, having been ran over the entire ROM file, was pretty messy containing a lot of nonsense code as a result of disassembling data (images, music, sound effects, etc) as if it were code, however, it was enough to peak my interest as a fun, interesting, long-term project.

Since then I've been working to turn this disassembly into a fully assemblable, editable and commented source code.

Credits and Thanks

The following people and pages have been of great help during the completion of this project. Huge thanks to them and their respective authors (listed in order of discovery):

Screenshots

Nothing to see here, yet...

Want To Know More?

If you want to know more about this project you can email me using the details in the contact page or drop by my dedicated topic on Romhacking.net.

Downloads

T.E.S.S.E. Toejam and Earl SaveState Editor created by me in VisualBasic.Net back when I was first learning about ROM hacking. Easy to use, lets you edit inventory and stats using simple menus. Works on GENS savestates. Screenshot of T.E.S.S.E