Program Setup – Neo-Geo Programming Guide
Program Setup
In order to make a "working" Neo-Geo binary, you don't really need to have much code. However, if you want to make sure no stone is unturned, keep reading...
68K Header
The 68K header begins at $0 and defines the Supervisor Stack Pointer,
Initial Program Counter, and various vector points.
| Location | Description | Notes |
|---|---|---|
$00 |
Initial Supervisor Stack Pointer | |
$04 |
Initial Program Counter | |
$08 |
Bus Error | |
$0C |
Address Error | Used by Debug BIOS for starting the Monitor. |
$10 |
Illegal Instruction | |
$14 |
Divide by 0 | YOU CAN'T DO THIS!!! but your game/program can catch it in case it does. |
$18 |
CHK Instruction |
|
$1C |
TRAPV Instruction |
|
$20 |
Privilege Violation | |
$24 |
Trace | |
$28 |
Line 1010 Emulator | Used when running an instruction of the format $Axxx. |
$2C |
Line 1111 Emulator | Used when running an instruction of the format $Fxxx. |
$30-$3B |
Reserved | |
$3C |
Uninitialized Interrupt Vector | |
$40-$5F |
Reserved | |
$60 |
Spurious Interrupt | |
$64 |
Level 1 Interrupt | Level 2 INT on NeoGeo CD! |
$68 |
Level 2 Interrupt | Level 1 INT on NeoGeo CD! |
$6C |
Level 3 Interrupt | |
$70 |
Level 4 Interrupt | |
$74 |
Level 5 Interrupt | |
$78 |
Level 6 Interrupt | |
$7C |
Level 7 Interrupt | |
$80-$FF |
Traps |
Neo-Geo Header
The Neo-Geo header begins at $100 and represents the bulk of the
required code for making a booting binary.
| Location | Description | Notes |
|---|---|---|
$100 |
"NEO-GEO" magic number/string | NEO-GEO |
$107 |
System Version (1 byte) | |
$108 |
NGH number (1 word [2 bytes]) | 0000 prohibited. |
$10A |
Program size in bytes (1 longword [4 bytes]) | |
$10E |
Pointer to 68K user backup RAM block (1 longword [4 bytes]) | First two bytes are Debug DIPs. |
$112 |
Size of save game in bytes (1 word [2 bytes]) | |
$114 |
Eye-catch animation flag (1 byte) | 0=Handled by BIOS; 1=Handled by game; 2=Nothing |
$115 |
Sprite bank number for BIOS eyecatch (1 byte) | Used if $114 is 0. Always shown on Universe BIOS. |
$116 |
Pointer to Japanese soft DIP (1 longword [4 bytes]) | |
$11A |
Pointer to USA soft DIP (1 longword [4 bytes]) | |
$11E |
Pointer to European soft DIP (1 longword [4 bytes]) | |
$122 |
JMP to USER subroutine | |
$128 |
JMP to PLAYER_START | |
$12E |
JMP to DEMO_END | |
$134 |
JMP to COIN_SOUND | |
$182 |
Pointer to Security Code (1 longword [4 bytes]) |
Security Code
You might find this being called "Trap Code" as well. It's just another thing
required by the system before you can boot the game. The value at $182
must point to it as well.
TrapCode: dc.l $76004A6D,$0A146600,$003C206D,$0A043E2D dc.l $0A0813C0,$00300001,$32100C01,$00FF671A dc.l $30280002,$B02D0ACE,$66103028,$0004B02D dc.l $0ACF6606,$B22D0AD0,$67085088,$51CFFFD4 dc.l $36074E75,$206D0A04,$3E2D0A08,$3210E049 dc.l $0C0100FF,$671A3010,$B02D0ACE,$66123028 dc.l $0002E048,$B02D0ACF,$6606B22D,$0AD06708 dc.l $588851CF,$FFD83607 dc.w $4e75
Software DIPs
Most arcade games use physical dip switches to change the game settings. Since the Neo-Geo uses multiple cartridges, these dip switches needed to be moved to the software side.
(todo)