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

• $D00000~$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: Last 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: ?