System Information:
Resolution: 320(304?)x224
Color Palette: 65,536
Maximum Colors On-Screen: 4,096
Maximum Sprites On-Screen: 380
Minimum Sprite Size: 1x2
Maximum Sprite Size: 16x512
Maximum Amount of Game Planes: 3(?)
Sound Channels: 4-FM synthesis, 7-Digital, 3-PSG, 1-Noise channel
Yamaha 2610 sound chip.
Internal RAM: Work RAM: 64Kb
58MBit DRAM, 512KBit VRAM and 64KBit SRAM (CD version only).
512KBit DRAM, 512KBit VRAM (Cartridge version).
Graphics information:
$00000 - $DFFF: Blocks of sprite data, each $80 bytes:
Each $80 block is made up of $20 double words, their format is:
Word: Sprite number (16 bits)
Byte: Palette number (8 bits)
Byte: Bit 0: X flip
Bit 1: Y flip
Bit 2: Automatic animation flag (4 tiles?)
Bit 3: Automatic animation flag (8 tiles?)
Bit 4: MSB of sprite number (confirmed, Karnov_r, Mslug). See note.
Bit 5: MSB of sprite number (MSlug2)
Bit 6: MSB of sprite number (Kof97)
Bit 7: Unknown for now
Each double word sprite is drawn directly underneath the previous one,
based on the starting coordinates.
$7000 - $7a00 : Front plane fix tiles (8*8), 2 bytes each
$8000: Control for sprites banks, arranged in words
Bit 0 to 3 - Y zoom LSB
Bit 4 to 7 - Y zoom MSB (ie, 1 byte for Y zoom).
Bit 8 to 11 - X zoom, $f is full size (no scale).
Bit 12 to 15 - Unknown, probably unused
$8200: Control for sprite banks, arranged in words
Bit 0 to 5: Number of sprites in this bank (see note below).
Bit 6 - If set, this bank is placed to right of previous bank
(same Y-coord).
Bit 7 to 15 - Y position for sprite bank.
$8400: Control for sprite banks, arranged in words
Bit 0 to 5: Unknown
Bit 7 to 15 - X position for sprite bank.
Memory Locations:
$10FD83 Nationality of the machine (0 = Japanese / 1 & 2 = English)
$10FDAE Set to zero before booting to force complete initialization.
$10FE80 Set to FF to activate debug mode.
$10F6EE (DWORD) Contains a copy of 68000 (IRQ Vector).
$300000 (Write) Watchdog Reset
$300001
$300000 Controller #1
bit 7 : Button D
bit 6 : Button C
bit 5 : Button B
bit 4 : button A
bit 3 : Right
bit 2 : Left
bit 1 : Down
bit 0 : Up
$300001 Dipswitches
bit 0 : Selftest
bit 1 : Unknown (Unused ?) \ something to do with
bit 2 : Unknown (Unused ?) / auto repeating keys ?
bit 3 : \
bit 4 : | communication setting ?
bit 5 : /
bit 6 : free play
bit 7 : stop mode ?
$300080 Controller #4 - Test switch in here
$300081
$31001c Unknown (ghost pilots)
$320000 Sound CPU
$320001
$320001
The Neo Geo contains an NEC 4990 Serial I/O calendar & clock accesed
through $320001, $380050, $280050 (shadow adress). A schematic
for this device can be found on the NEC webpages.
bit 0 : COIN 1
bit 1 : COIN 2
bit 2 : SERVICE
bit 3 : UNKNOWN
bit 4 : UNKNOWN
bit 5 : UNKNOWN
bit 6 : 4990 test pulse bit.
bit 7 : 4990 data bit.
$340000 Controller #2 (same bits as $300000)
$380000 Status byte
0 PAD1 START
1 PAD1 SELECT
2 PAD2 START
3 PAD2 SELECT
4 --\ MEMORY CARD
5 --/ INSERTED
6 MEMORY CARD WRITE PROTECTION
7 UNUSED (?)
$380011 Backup bank select
$380051 4990 control write register
bit 0: C0
bit 1: C1
bit 2: C2
bit 3-7: unused.
$00 = register hold.
$02 = shift.
$03 = time read (reset register).
$04 = ????.
$3a0001 Enable display.
$3a0003 Swap in Bios ($80 bytes vector table of BIOS)
$3a000a Select board FIX char rom
$3a000b
$3a000c Neogeo Sram Lock
$3a000d
$3a000e Neogeo Setpalbank1
$3a000f
$3a001a Select game FIX char rom
$3a001b
$3a001c Neogeo Sram Unlock
$3a001d
$3a001e Neogeo SetPalbank0 Palette banking
$3a001f
$3a0011 Disable display
$3a001b set bios vector table (?) mirror ?
$3a001d unlock backup ram
$3a0013 Swap in Rom ($80 bytes vector table of ROM bank)
$3c000c IRQ acknowledge
4 = IRQ 1
2 = IRQ 2
1 = IRQ 3 (does any game use this?)
$3c000e $3c000f Control R
The format of this very important location is: AAAA AAAA B??? CDDD
A is most likely the video beam line, however from how it is used it
doesn't seem to be a 0-255 direct map: the top bit is often masked out.
I think the top bit of A is: (vblank OR irq2). sdodgeb loops waiting for
it to be 1; zedblade heavily depends on it to work correctly.
B is used together with A in one place, so most likely video beam position
Maybe AAAAAAAAB is a 9-bit video line counter.
It is tested individually in many cases (e.g. samsho3) so it might not be
the low bit of the raster line.
C is definitely a PAL/NTSC flag. Evidence:
1) trally changes the position of the speed indicator depending on
it (0 = lower 1 = higher).
2) samsho3 sets a variable to 60 when the bit is 0 and 50 when
it's 1. This is obviously the video refresh rate in Hz.
3) samsho3 sets another variable to 256 or 307. This could be the
total screen height (including vblank), or close to that.
Some game (e.g. lstbld2, samsho3) do this (or similar):
bclr #$0, $3c000e.l
when the bit is set, so 3c000e (whose function is unknown) has to
be related
D is unknown (counter of some kind, used in a couple of places).
in blazstar, this controls the background speed in level 2.
IO addresses
$3c0000 Read/Write location in VRAM.
$3c0002 Read/Write into VRAM
$3c0004 Value to increment VRAM address by (based on words)
$3c0006 Unknown, set vblank counter (?)
$3c0008 shadow adress for $3c0000.
$3c000a shadow adress for $3c0002.
68k Addresses
$000000 $0fffff Rom bank 1
$100000 $10ffff Ram bank 1
$200000 $2fffff Rom bank 2
$2ffff0 $2fffff Neo Bankswitch Write
$400000 $401fff Neogeo Palette Ram Read
$800000 $800fff NeoGeo Memcard Read
Memory card is a 2kb battery backed RAM.
It is accessed thru $800000-$800FFF.
Even bytes are always $FF
Odd bytes are memcard data ($800 bytes)
$c00000 $c1ffff System Bios Rom
$d00000 $d0ffff 64k battery backed SRAM
trally writes to 200000-200003 as well, probably looking for a serial
link both games write to 0000fe before writing to 200000. The two
things could be related. Sidekicks reads and writes to several
addresses in this range, using this for copy protection.
Z80 Addresses
$0000 $7fff Rom
$8000 $bfff Bank 5
$c000 $dfff Bank 6
$e000 $efff Bank 7
$f000 $f7ff Bank 8
$f800 $ffff Ram
Character layout
8 x 8 chars
4096 in total
4 bits per pixel (planes are packed in a nibble)
32 bytes per char
Sprite Layout
16 x 16
4 bits per pixel
128 bytes per sprite
$00 Stack pointer
$04 Initial PC ($C11002)
$64 VBlank pointer
$100 "NEO-GEO",0
$108 NGH Number, a unique number assigned to each cart. (WORD) (Thanks to Apollo69 for this info.)
$10A ?
$10C ?
$10E Pointer to debug dip switches ?
$112 ?
$114 Starting Sprite Number / $100 for the Neo Geo logo.
Logo is (64 x 64 chars. 4096 bytes total in each bank).
$116 Pointer to Japanese name
$11A Pointer to English name
$122 Entry point of the software
$182 Pointer to security code.
