Backup RAM
The backup RAM is a battery-powered 64KiB RAM space used by MVS systems to store game scores, cab infos and income logs. Access is handled by the BIOSes.
Memory region: $D00000~$D0FFFF (Mirrored up to $DFFFFF ?).
Data structure
All offset are taken from the sp-s2.bin bios.
| Start | End | Size | Data | Description |
| $D00000 | $D0000F | $F | $00 | Unused, fill with $00 |
| $D00010 | $D0001F | $F | "BACKUP RAM OK!Ç" | The routine at $C125C8 will check if this string is present, if not it will test the ram (using the test_ram routine at $C13134) and re-init the backupram |
| $D00020 | $D00039 | $19 | $00 | Unused, fill with $00 |
| $D0003A | $D00045 | $C | $01010102010101030000303B0000 | the init_backupram routine ($C125F4) will copy $C data from $C1F000 there. |
| $D00122 | $D00123 | $2 | $23 | The init_backupram routine write $23 there, purpose unknown. |
| $D00124 | $D00127 | $4 | Slot-1 NGH number and game name ID (see below) | If not present $0000 as NGH and $FFFF as game name ID |
| $D00128 | $D0012B | $4 | Slot-2 NGH number and game name ID (see below) | If not present $0000 as NGH and $FFFF as game name ID.
On a slot1 always unset (slot1 are slot2 with the second one empty) |
| $D0012C | $D0012F | $4 | Slot-3 NGH number and game name ID (see below) | If not present $0000 as NGH and $FFFF as game name ID |
| $D00130 | $D00133 | $4 | Slot-4 NGH number and game name ID (see below) | If not present $0000 as NGH and $FFFF as game name ID |
| $D00134 | $D00137 | $4 | Slot-5 NGH number and game name ID (see below) | If not present $0000 as NGH and $FFFF as game name ID |
| $D00138 | $D0013B | $4 | Slot-6 NGH number and game name ID (see below) | If not present $0000 as NGH and $FFFF as game name ID |
| $D0013C | $D0013F | $4 | Slot-7 NGH number and game name ID (see below) | If not present $0000 as NGH and $FFFF as game name ID |
| $D00140 | $D00143 | $4 | Slot-8 NGH number and game name ID (see below) | If not present $0000 as NGH and $FFFF as game name ID |
| $D00144 | $D00147 | $4 | YYMMDDdd | Slot-1 book creation time YEAR-MONTH-DAY-day number |
| $D00148 | $D0014B | $4 | YYMMDDdd | Slot-2 book creation time YEAR-MONTH-DAY-day number |
| $D0014C | $D0014F | $4 | YYMMDDdd | Slot-3 book creation time YEAR-MONTH-DAY-day number |
| $D00150 | $D00153 | $4 | YYMMDDdd | Slot-4 book creation time YEAR-MONTH-DAY-day number |
| $D00154 | $D00157 | $4 | YYMMDDdd | Slot-5 book creation time YEAR-MONTH-DAY-day number |
| $D00158 | $D0015B | $4 | YYMMDDdd | Slot-6 book creation time YEAR-MONTH-DAY-day number |
| $D0015C | $D0015F | $4 | YYMMDDdd | Slot-7 book creation time YEAR-MONTH-DAY-day number |
| $D00160 | $D00163 | $4 | YYMMDDdd | Slot-8 book creation time YEAR-MONTH-DAY-day number |
| $D002A0 | $D002AF | $F | Game Name 0 | |
| $D002B0 | $D002BF | $F | Game Name 1 | |
| $D002C0 | $D002CF | $F | Game Name 2 | |
| $D002D0 | $D002DF | $F | Game Name 3 | |
| $D002E0 | $D002EF | $F | Game Name 4 | |
| $D002F0 | $D002FF | $F | Game Name 5 | |
| $D00300 | $D0030F | $F | Game Name 6 | |
| $D00310 | $D0031F | $F | Game Name 7 |
- $D00000~$D0000F: Nothing ($00)
- $D00010: "BACKUP RAM OK !",$80
- $D00020.l: ?
- $D00021.b: btst 0,1,2,3,4
- $D00024.l: adresse ?
- $D00034.l: adresse ?
- $D00038.w: ? bit 4 tst
- $D0003A: Start of ? (13 bytes)
- $D00042.b: tst ?
- $D00043.b: tst ?
- $D00044.w: ?
- $D00046.b: SOUND_STOP, No sound at all if non-zero
- $D00047.b: Number of detected slots
- $D00048.l: ?
- $D0004C.b: ? ($3B)
- $D00058.b: First valid slot
- $D0005E.b: Something to do with tested slot? tst
- $D0005A.b: heure ?
- $D00060.w: multi-slot flag
- $D00104: year,month,day ? (3 bytes) Modify date
- $D00108.b: Selected tested slot
- $D00109.b: Compared with 8
- $D0011A: Start of ?
- $D00122.b: ? ($23)
- $D00124: adresses ? (4 bytes * nb of slots ?)
- $D00144: Date (Year, Month, Day, ? *8 ?) Creation date
- $D001AC.l: $F0F0F0F0
- $D001B0.w: $FFFF
- $D002A0: Title of game (16 bytes *8 ?)
- $D00320: ?