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: ?