Memory card
The NeoGeo (AES and some MVS) uses JEIDA V3 memory cards to store game saves and/or high scores. The original SNK-branded card could only hold 2KiB of data.
The official SNK memory card was a battery-based 2KiB card using a LH5116 CMOS SRAM chip and voltage switching circuitry. Data retention voltage: 2V. The SP-S2 system ROM can handle memory cards up to 16KiB. The card is embedded in CD systems as a 8KiB battery-backed RAM chip.
See the CARD call description for memory card operations.
Data format
The system ROM can handle 8 different card sizes (2K, 4K, 6K, 8K, 10K, 14K and 16K) and 4 different card types (8 bits wide, 16 bits wide, 16 bits wide "doubled", and "SNK ROM" cards).
All cards use the same format regardless of capacity.
The data is split into 5 regions:
Header
Always 128 bytes.
| Address | Name | Size | Description |
| $0~$9 | 10 bytes | Zeros or "SNK ROM " (development unit ?)
For 16 bits "doubled" cards, $6 is set to $0001 | |
| $A | CARD_SIZE | word | Card capacity |
| $C | byte | 0 | |
| $D | CARD_FAT_1_CHKSUM | byte | Checksum of FAT 1 |
| $E | CARD_FAT_2_CHKSUM | byte | Checksum of FAT 2 |
| $F | CARD_USERNAME_AVAILABLE | byte | 0 : Username unavailable, !0 : Username available |
| $10 | CARD_USERNAME | 16 bytes | Card holder's username |
| $20 | CARD_MAGIC | 16 bytes | $4E $XX $45 $XX $4F $XX $2D $XX $47 $XX $45 $XX $4F $XX $80 $XX ("NEO-GEO", $80) |
| $30 | CARD_REGION | byte | Region of the system that formated the card, 0 = Japan, 1 = USA, 2 = Europe |
Directory
List of saves of 32, 64, 96, 128, 160, 192, 224 or 256 entries. The size depends on the card's capacity.
Each entry has the following format:
| Address | Size | Description |
| $0 | byte | Save sub number (CARD_SUB), 0 to 15. $FF if entry is free. |
| $1 | word | Game's NGH number |
| $3 | byte | FAT entry number (see below) |
FAT 1
List of used blocks, of 64, 128, 192, or 256 entries. The size depends on the card's capacity.
- $02 is a block reservd by the system ROM
- $01 is a block used by a game
- $00 is a free block
FAT 2
FAT 2 is simply a mirror of FAT 1.
Game Data
Many games use 64 bytes, but some might use more.
The first 20 bytes are the data title (usually the game and stage name).
Registers
- Write is enabled if REG_CRDUNLOCK1 is 0 and REG_CRDUNLOCK2 is 1
- The WP (Write Protect) pin is read through bit 6 of REG_STATUS_B
- CD1 (Card Detect 1) is read through bit 4 of REG_STATUS_B
- CD2 (Card Detect 2) is read through bit 5 of REG_STATUS_B
- Attribute memory is selected if REG_CRDREGSEL is 1
Card pinout (top)
| Pin # | Name | Signal | Description | Goes to |
|---|---|---|---|---|
| 1 | GND | |||
| 2 | D3 | CDD3 | Data bus | NEO-G0 |
| 3 | D4 | CDD4 | ||
| 4 | D5 | CDD5 | ||
| 5 | D6 | CDD6 | ||
| 6 | D7 | CDD7 | ||
| 7 | /CE1 | CRDC | Chip enable 1 | NEO-C1 |
| 8 | A10 | CDA10 | Address | NEO-E0 |
| 9 | /OE | CRDO | Output enable | NEO-C1 |
| 10 | A11 | CDA11 | Address bus | NEO-E0 |
| 11 | A9 | CDA9 | ||
| 12 | A8 | CDA8 | ||
| 13 | A13 | CDA13 | ||
| 14 | A14 | CDA14 | ||
| 15 | /WE | Write enable | HC32 | |
| 16 | /BUSY | Low when card is busy | Not used | |
| 17 | VCC | |||
| 18 | VPP | |||
| 19 | A16 | CDA16 | Address bus | NEO-E0 |
| 20 | A15 | CDA15 | ||
| 21 | A12 | CDA12 | ||
| 22 | A7 | CDA7 | ||
| 23 | A6 | CDA6 | ||
| 24 | A5 | CDA5 | ||
| 25 | A4 | CDA4 | ||
| 26 | A3 | CDA3 | ||
| 27 | A2 | CDA2 | ||
| 28 | A1 | CDA1 | ||
| 29 | A0 | CDA0 | ||
| 30 | D0 | CDD0 | Data bus | NEO-G0 |
| 31 | D1 | CDD1 | ||
| 32 | D2 | CDD2 | ||
| 33 | WP | WP | High if card is write-protected | NEO-C1 |
| 34 | GND | |||
Card pinout (bottom)
| Pin # | Name | Signal | Description | Goes to |
|---|---|---|---|---|
| 35 | GND | |||
| 36 | /CD1 | CD1 | Card detect | NEO-C1 |
| 37 | D11 | CDD11 | Data bus | NEO-G0 |
| 38 | D12 | CDD12 | ||
| 39 | D13 | CDD13 | ||
| 40 | D14 | CDD14 | ||
| 41 | D15 | CDD15 | ||
| 42 | /CE2 | CRDC | Chip enable 2 | NEO-C1 |
| 43 | /VS1 | Not used | ||
| 44 | /IORD | |||
| 45 | /IOWR | |||
| 46 | A17 | CDA17 | Address bus | NEO-E0 |
| 47 | A18 | CDA18 | ||
| 48 | A19 | CDA19 | ||
| 49 | A20 | CDA20 | ||
| 50 | A21 | CDA21 | ||
| 51 | VCC | |||
| 52 | VCC | |||
| 53 | A22 | CDA22 | Address bus | NEO-E0 |
| 54 | A23 | CDA23 | ||
| 55 | A24 | Not used | ||
| 56 | A25 | |||
| 57 | /VS2 | |||
| 58 | RESET | |||
| 59 | /WAIT | |||
| 60 | NC | Reserved | ||
| 61 | /REG | Select attribute memory | HC32 | |
| 62 | BVD2 | Battery voltage detect | Not used | |
| 63 | BVD1 | |||
| 64 | D8 | CDD8 | Data bus | NEO-G0 |
| 65 | D9 | CDD9 | ||
| 66 | D10 | CDD10 | ||
| 67 | /CD2 | CD2 | Card detect | NEO-C1 |
| 68 | GND | |||