SCHG:Sonic Crackers

This is the Sonic Community Hacking Guide for Sonic Crackers. This guide was originally written by Hivebrain, and is used here with permission. The original guide can be found here.

ROM Contents

Offset	Purpose
$0	Header
$200	Code
$1E14	Collision array
$3E14	Curve and resistance mapping
$3F14	Code
$3F2A	Something affecting Sonic's movement
$44C4	Palette (1) - unknown
$44E4	Code
$4684	Palettes (4) - unknown
$4704	Code
$6F62	Palettes (2) - Sega logo
$6FA2	Crackers Compressed Art - Sega logo
$7348	Code
$749C	Palettes (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	Palettes (2) - Sonic & Tails; arms & rings
$7ED8	Code - field levels
$835C	Palette - Rainbow Field cycling
$837C	Code
$83EA	Palette - Electric Field cycling
$856A	Code
$8572	Palette - Electric Field cycling
$85D4	Code
$8988	Palettes (2) - Sonic & Tails on field levels
$89C8	Code
$8D08	Palettes (8) - Techno Tower Zone
$8E08	Code
$90B6	Nemesis Compressed Art - borders from menu screens
$90EA	Mappings - "SELECT" menu screens
$93CA	Code
$9C68	Palettes (2) - Speed Slider Zone
$9CA8	Code
$9CF0	Palettes (2) - Techno Tower Zone (unused)
$9D30	Code
$EDE4	Palette - TTZ cycling
$EE0C	Code
$EE4C	Palette - TTZ cycling
$EE5C	Code
$EEBA	Palette - TTZ cycling
$EEDA	Code
$EF38	Palette - TTZ cycling
$EF58	Code
$EFA4	Palette - 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	Palettes (2) - Rainbow Field
$4596C	Crackers Compressed Art - 8x8 tiles for Rainbow Field (Entry 00)
$4732E	Crackers Compressed Art - 8x8 tiles for Rainbow Field (Entry 01)
$48FEA	Mappings - Rainbow Field foreground (Entry 00)
$497F2	Mappings - Rainbow Field foreground (Entry 01)
$49FFA	Mappings - Rainbow Field foreground (Entry 02)
$4A802	Mappings - Rainbow Field foreground (Entry 03)
$4B00C	Mappings - Rainbow Field background (Entry 00)
$4B814	Mappings - Rainbow Field background (Entry 01)
$4C014	Palettes (2) - Electric Field
$4C05A	Crackers Compressed Art - 8x8 tiles for Electric Field (Entry 00)
$4F3D8	Crackers Compressed Art - 8x8 tiles for Electric Field (Entry 01)
$51094	Mappings - Electric Field foreground (Entry 00)
$5189C	Mappings - Electric Field foreground (Entry 01)
$520A4	Mappings - Electric Field foreground (Entry 02)
$528AC	Mappings - Electric Field foreground (Entry 03)
$530B6	Mappings - Electric Field background (Entry 00)
$5373E	Mappings - Electric Field background (Entry 01)
$53DC6	Mappings - Electric Field background (Entry 02)
$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)

Offset	Purpose
$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	Palettes

Savestate Contents (Techno Tower Zone)

Offset	Purpose
$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	Palettes

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 palette 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 and Tails' sprite. Each load cue consists of ten bytes

S2S1

97L3

L2L1

DDDD

FFFF

S2S1 = DMA Size

• This is the number of bytes of the art to transfer to V-Ram, the size (number of bytes) is divided by 2 and then the bytes are swapped.
• For example 0280 (Size), divided by 2 is 0140, and then swapped to 4001. (This will be unpacked to 93409410 ready for DMA).

97L3 and L2L1 = DMA Location (Source)

• This is the source address (where the art is being transfered from), it is divided by 2 and then broken into 4 bytes L4L3L2L1, L4 is ignored completely as you cannot have an address that extends that far on the MC68 (it'll mask it), L3 is put with 97 (DMA register), while L2 is put with L1.
• For example 00018040 (Source Location), divided by 2 is 0000C020, the far 00 is ignored 00C020, and 97 is put on the end 9700C020. (This will all be unpacked to 970096C09520 ready for DMA).

DDDD = DMA Destination

• This is the destination address (where the art is being transfered to in V-Ram), although this is simply aligned (or arranged) to the VDP port format, there is hard coded data at the rom offset address 0000CA2C, the data there is "added" to the destination address before it's aligned correctly, those hard coded locations can allow you to send ALL art data to another address in V-Ram without having to change all of the PLC entries.
• This data will be unpacked like so; D380, add hard coded address 0420 = D7A0, the data is now a long-word in size with the destination on the left word D7A00000, the two most significant bits are sent to the far right 17A00003, add (or) the VDP address mode bits 57A00003, add (or) the DMA mode bit 57A00083, it is then sent to VDP for processing.

FFFF = End of list flag

• If it is a non-zero value (i.e. not 0000), then it is the end of the list, if not, it'll continue to the next entry.

V-Ram "add" address at 0000CA2C

• The format for the V-Ram "add" data held at offset 0000CA2C consists of 10 bytes, each word (two bytes) is a V-Ram add address for each "character" in game, there can be a total of 8 characters, the first word being the first character, the last word being the eighth character (The reason the word "character" has been used here, is because Sonic and Tails can switch character slots in game in real time, so they are not hard coded to a particular slot).

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.

Sonic Community Hacking Guide
General
Number Systems | Sonic Music Hacking Guide | Assembly Hacking Guide | Subroutine Equivalency List | 68000 Instruction Set | SonED2 Manual | 68000 ASM-to-Hex Code Reference | VDP Documentation | Official Sega 32X Documentation | Official Sega CD Documentation | Official Sega Genesis Documentation
Game-Specific
Sonic the Hedgehog (16-bit) | Sonic the Hedgehog (8-bit) | Sonic Eraser | Sonic CD (prototype 510) | Sonic CD | Sonic CD (PC) | Sonic 2 (Nick Arcade prototype) | Sonic 2 (Simon Wai prototype) | Sonic 2 (16-bit) | Sonic 2 (8-bit) | Sonic 2 & Knuckles | Dr. Robotnik's Mean Bean Machine | Sonic Triple Trouble | Sonic 3 | Sonic & Knuckles | Sonic 3 & Knuckles | Sonic & Knuckles Collection | Sonic Crackers | Sonic 3D: Flickies' Island | Knuckles' Chaotix | Sonic R PC | Sonic Jam 6 | Sonic Advance | Sonic Advance 2 | Sonic Advance 3 | Sonic Battle | Sonic Adventure | Sonic Adventure DX | Sonic Adventure DX: PC | Sonic Adventure (2010) | Sonic Adventure 2 | Sonic Adventure 2: Battle | Sonic Heroes | Shadow the Hedgehog | Sonic & SEGA All-Stars Racing | Sonic Unleashed (XBOX 360/PS3) | Sonic Generations
The Nemesis Hacking Guides
ROM: Sonic 1 | Sonic 2 | Sonic 2 Beta | Sonic 3 Savestate: Sonic 1 | Sonic 2 Beta/Final | Sonic 3
The Esrael Hacking Guides
Sonic 1 (English / Portuguese) | Sonic 2 Beta (English / Portuguese) | Sonic 2 and Knuckles (English / Portuguese)