Sonic Crackers/Technical information
From Sonic Retro
This guide was originally written by Hivebrain, and is used here with permission. The original guide can be found here.
Contents
ROM Contents
| 0 | Header | |
| 200 | Code | |
| 1E14 | Collision array | |
| 3E14 | Curve and resistance mapping | |
| 3F14 | Code | |
| 3F2A | Something affecting Sonic's movement | |
| 44C4 | Pallete (1) - unknown | |
| 44E4 | Code | |
| 4684 | Palletes (4) - unknown | |
| 4704 | Code | |
| 6F62 | Palletes (2) - Sega logo | |
| 6FA2 | Compressed Art - Sega logo | |
| 7348 | Code | |
| 749C | Palletes (2) - main menu | |
| 74DC | Code - title and menu screens | |
| 75DA | Nemesis Compressed Art - alphabet from main menu screens | |
| 78E8 | Mappings - title screen | |
| 7E08 | Code - field levels | |
| 7E98 | Palletes (2) - Sonic & Tails; arms & rings | |
| 7ED8 | Code - field levels | |
| 835C | Pallete - Rainbow Field cycling | |
| 837C | Code | |
| 83EA | Pallete - Electric Field cycling | |
| 856A | Code | |
| 8572 | Pallete - Electric Field cycling | |
| 85D4 | Code | |
| 8988 | Palletes (2) - Sonic & Tails on field levels | |
| 89C8 | Code | |
| 8D08 | Palletes (8) - Techno Tower Zone | |
| 8E08 | Code | |
| 90B6 | Nemesis Compressed Art - borders from menu screens | |
| 90EA | Mappings - "SELECT" menu screens | |
| 93CA | Code | |
| 9C68 | Palletes (2) - Speed Slider Zone | |
| 9CA8 | Code | |
| 9CF0 | Palletes (2) - Techno Tower Zone (unused) | |
| 9D30 | Code | |
| EDE4 | Pallete - TTZ cycling | |
| EE0C | Code | |
| EE4C | Pallete - TTZ cycling | |
| EE5C | Code | |
| EEBA | Pallete - TTZ cycling | |
| EEDA | Code | |
| EF38 | Pallete - TTZ cycling | |
| EF58 | Code | |
| EFA4 | Pallete - TTZ cycling | |
| EFD4 | Code | |
| FDB0 | Music data | |
| 15630 | Unknown | |
| 30000 | Uncompressed Art - Numbers and letters from the HUD | |
| 30E80 | Nemesis Compressed Art - Orbs / fireballs or something (no pointer points to this item) | |
| 30EE2 | Nemesis Compressed Art - SSZ 8x8 tiles | |
| 3452C | Enigma Compressed Data - SSZ 16x16 tiles | |
| 35762 | Enigma Compressed Data - SSZ 128x128 tiles | |
| 39086 | Enigma Compressed Data - SSZ level layout | |
| 3931E | SSZ primary collision index | |
| 3971E | SSZ secondary collision index | |
| 39B1E | Nemesis Compressed Art - SSZ 8x8 bg tiles | |
| 3A5FE | Enigma Compressed Data - SSZ 16x16 bg tiles | |
| 3A6E8 | Enigma Compressed Data - SSZ 128x128 bg tiles | |
| 3A7B8 | Enigma Compressed Data - SSZ bg layout | |
| 3A7CE | Nemesis Compressed Art - TTZ 8x8 tiles | |
| 3BB24 | Enigma Compressed Data - TTZ 16x16 tiles | |
| 3C60A | Enigma Compressed Data - TTZ 128x128 tiles | |
| 3ED12 | Enigma Compressed Data - TTZ level layout | |
| 3EEC4 | TTZ primary collision index | |
| 3F2C4 | TTZ secondary collision index | |
| 3F6C4 | Nemesis Compressed Art - TTZ 8x8 bg tiles | |
| 409E2 | Enigma Compressed Data - TTZ 16x16 bg tiles | |
| 4108C | Enigma Compressed Data - TTZ 128x128 bg tiles | |
| 4183E | Enigma Compressed Data - TTZ bg layout | |
| 41954 | Uncompressed Art - splash screen | |
| 41B9C | Nemesis Compressed Art - springs | |
| 41F76 | Nemesis Compressed Art - horizontal spikes | |
| 4221E | Nemesis Compressed Art - vertical spikes | |
| 42486 | Uncompressed Art - animated patterns in TTZ | |
| 44946 | Uncompressed Art - "COMBI" (unused) | |
| 44A66 | Uncompressed Art - end-of-level splash screen? (unused) | |
| 44F66 | Uncompressed Art - numbers | |
| 451E6 | Uncompressed Art - exclaimation mark and minute symbol | |
| 45246 | Uncompressed Art - stars and rings (some unused) | |
| 45906 | Uncompressed Art - seconds symbol | |
| 45926 | Palletes (2) - Rainbow Field | |
| 45966 | Compressed Art (Unknown Format) - 8x8 tiles for Rainbow Field | |
| 48FE0 | Mappings - Rainbow Field foreground | |
| 4B002 | Mappings - Rainbow Field background | |
| 4C014 | Palletes (2) - Electric Field | |
| 4C054 | Compressed Art (Unknown Format) - 8x8 tiles for Electric Field | |
| 5108A | Mappings - Electric Field foreground | |
| 530AC | Mappings - Electric Field background | |
| 54460 | Empty | |
| 60000 | Uncompressed Art - Sonic's arms | |
| 64000 | Uncompressed Art - Tails' arms | |
| 66680 | Index system for frames used for Sonic's arm | |
| 667D8 | Pattern load cues - Sonic's arm | |
| 66B34 | Mappings - Sonic's arm | |
| 66D5C | Something to do with how Sonic's arm is connected to Sonic | |
| 66E26 | Index system for frames used for Sonic | |
| 66F92 | Pattern load cues - Sonic | |
| 67302 | Mappings - Sonic | |
| 6777C | Index system for frames used for Tails' arm | |
| 6788C | Pattern load cues - Tails' arm | |
| 67B34 | Mappings - Tails' arm | |
| 67CD2 | Something to do with how Tails' arm is connected to Tails | |
| 67DD2 | Index system for frames used for Tails | |
| 67FBE | Pattern load cues - Tails | |
| 6852C | Mappings - Tails | |
| 68A06 | Code | |
| 68A42 | Index system for frames used for Sonic on field levels | |
| 68ABA | Pattern load cues - Sonic on field levels | |
| 68BE6 | Mappings - Sonic on field levels | |
| 68CFA | Code | |
| 68D36 | Index system for frames used for Tails on field levels | |
| 68DC6 | Pattern load cues - Tails on field levels | |
| 68EF2 | Mappings - Tails on field levels | |
| 68FD6 | Empty | |
| 80000 | Uncompressed Art - Sonic | |
| 90000 | Uncompressed Art - Sonic on field levels | |
| 98000 | Uncompressed Art - Text | |
| A0000 | Uncompressed Art - Tails | |
| B0000 | Uncompressed Art - Tails on field levels | |
| B3820 | Empty or unused data until end of ROM |
Savestate Contents (Speed Slider Zone)
| 2478 | Unknown | |
| 2678 | Collision Data | |
| 2E78 | Unknown | |
| 3180 | 16x16 Tile Mappings | |
| 4938 | 128x128 Tile Mappings | |
| BC38 | Level Layout | |
| C238 | 16x16 Background Tile Mappings | |
| C4F8 | 128x128 Background Tile Mappings | |
| C878 | Background Layout | |
| F85C | Palletes |
Savestate Contents (Techno Tower Zone)
| 2478 | Unknown | |
| 2678 | Collision Data | |
| 2E78 | Unknown | |
| 3180 | 16x16 Tile Mappings | |
| 3FD0 | 128x128 Tile Mappings | |
| 9B50 | Level Layout | |
| 9D50 | 16x16 Background Tile Mappings | |
| A748 | 128x128 Background Tile Mappings | |
| B748 | Background Layout | |
| F85C | Palletes |
Mappings for Title Screen, Menu and Field Levels
Each image on the game select screen is made up of 8x8 pixel tiles. The way these tiles are arranged is called mappings. Each 8x8 tile is given a two-byte value based on where it appears in the VRAM:
Starting at 0000, so that on the title screen 0003 is a hash symbol (#). To change which pallete the tile uses, add 2000 to its value.
Pattern Load Cues for Sonic and Tails
Pattern load cues tell the game which graphics are to be loaded into the VRAM from the ROM for each frame of Sonic's sprite. Each load cue consists of ten bytes
| QQQQ | 9704 | RRR0 | D380 | FFFF |
QQQQ = The number of tiles that should be read from the ROM, where:
- 1000 = 1 tile
- 2000 = 2 tiles
- 0001 = 10 tiles
- 1001 = 11 tiles
- 1002 = 21 tiles
RRR = Where to start reading tiles from in the ROM, where 000 is the first of Sonic's tiles in the ROM; 001 is the second etc. The purpose of all the other bytes is unknown.
Mappings for Sonic and Tails
Mappings define how the 8x8 tiles are arranged to make up the characters' sprites. Each mappings block consists of six bytes:
| SS YY | TT TT | XX ZZ |
SS = Size and shape of the piece of sprite, where:
- 00 = 1 tile high, 1 tile wide
- 01 = 2 tiles high, 1 tile wide
- 02 = 3 tiles high, 1 tile wide
- 03 = 4 tiles high, 1 tile wide
- 04 = 1 tile high, 2 tiles wide
- 0E = 3 tiles high, 4 tiles wide
- 0F = 4 tiles high, 4 tiles wide (this is the largest possible sprite piece)
YY and XX = Position of the sprite piece.
TTTT = Which tiles from the VRAM are to be displayed on the screen. 0000 is the first tile in the VRAM, 0001 is the second etc.
ZZ = Defines whether there are additional pieces of sprite in the current frame of animation or not. 00 tells the game to assume the next mappings block is part of the same sprite frame. FF tells the game to end the current sprite frame and start a new one.