BIOS RAM locations

Address	DEF name	Size	Set by	Description
$10FD80	BIOS_SYSTEM_MODE	byte	BIOS	0:system mode, 1:game mode
$10FD82	BIOS_MVS_FLAG	byte	BIOS	0:AES, 1:MVS
$10FD83	BIOS_COUNTRY_CODE	byte	BIOS	0:Japan, 1:USA, 2:Europe
$10FD84~$10FD93	BIOS_GAME_DIP	16 bytes	BIOS	Software DIPs values
$10FD94	BIOS_P1STATUS	byte	BIOS	0:no connection, 1:normal joypad, 2:expanded joypad, 3:Mahjong controller, 4:Keyboard
$10FD95	BIOS_P1PREVIOUS	byte	BIOS	DCBA Right Left Bottom Top (positive logic)
$10FD96	BIOS_P1CURRENT	byte	BIOS	DCBA Right Left Bottom Top (positive logic)
$10FD97	BIOS_P1CHANGE	byte	BIOS	Active edge DCBA Right Left Bottom Top (positive logic)
$10FD98	BIOS_P1REPEAT	byte	BIOS	Active edge + repeat every 8 frames after 16 frames. DCBA Right Left Bottom Top (positive logic)
$10FD99	BIOS_P1TIMER	byte	BIOS	Countdown ?
$10FD9A~$10FD9F	Same for P2	5 bytes	BIOS	See above
$10FDA0~$10FDA6	Same for P3	5 bytes	BIOS	See above
$10FDA7~$10FDAB	Same for P4	5 bytes	BIOS	See above
$10FDAC	BIOS_STATCURNT	byte	BIOS	Select P4, Start P4, Select P3, Start P3, Select P2, Start P2, Select P1, Start P1 (positive logic)
$10FDAD	BIOS_STATCHANGE	byte	BIOS	Select P4, Start P4, Select P3, Start P3, Select P2, Start P2, Select P1, Start P1 (positive logic)
$10FDAE	BIOS_USER_REQUEST	byte	BIOS	Set by the USER subroutine. 0:Init, 1:Boot animation, 2:Demo, 3:Title
$10FDAF	BIOS_USER_MODE	byte	Game	0:Init/Boot animation, 1:Title/Demo, 3:Game
$10FDB0	BIOS_CREDIT_DEC	4 bytes	Game	Credit decrement value for each player when calling CREDIT DOWN.
$10FDB4	BIOS_START_FLAG	byte	BIOS	Used when calling the PLAYER START subroutine. Last 4 bits correspond to the player who pushed start.
$10FDB6	BIOS_PLAYER_MOD	4 bytes	Game	Sets player status. 0:Never played, 1:Playing, 2:Continue option being displayed, 3:Game over
$10FDBE	BIOS_MESS_POINT	longword	Game	MESS_OUT buffer pointer
$10FDC2	BIOS_MESS_BUSY	byte	Game	0:Allow MESS_OUT, 1:Skip MESS_OUT
$10FEE4		byte	BIOS	Frame counter (internal)

Memory card related

• BIOS_CRDF equ $10FDC4 ;byte: function to perform when calling BIOSF_CRDACCESS, see below table
• BIOS_CRDRESULT equ $10FDC6 ;byte: 00 on success, else 80+ and encodes the error, see below table
• BIOS_CRDPTR equ $10FDC8 ;longword: pointer to read from/write to
• BIOS_CRDSIZE equ $10FDCC ;word: how much data to read/write from/to card
• BIOS_CRDNGH equ $10FDCE ;word: usually game NGH. Unique identifier for the game that 'owns' the save file
• BIOS_CRDFILE equ $10FDD0 ;word: each NGH has up to 16 save 'files' associated with

Calendar, only on MVS (in BCD)

• BIOS_YEAR equ $10FDD2 ;last 2 digits of year
• BIOS_MONTH equ $10FDD3
• BIOS_DAY equ $10FDD4
• BIOS_WEEKDAY equ $10FDD5 ;Sunday = 00, Monday = 01 ... Saturday = 06
• BIOS_HOUR equ $10FDD6 ;24 hour time
• BIOS_MINUTE equ $10FDD7
• BIOS_SECOND equ $10FDD8

• BIOS_SELECT_TIMER equ $10FDDA ;Byte: game start countdown
• BIOS_DEVMODE equ $10FE80 ;Byte: non-zero for developer mode

Upload to DRAM

• BIOS_UPDEST equ $10FEF4 ;longword: destination address (!)
• BIOS_UPSRC equ $10FEF8 ;longword: source address
• BIOS_UPSIZE equ $10FEFC ;longword: size
• BIOS_UPZONE equ $10FEDA ;byte: zone (0=PRG, 1=FIX, 2=SPR, 3=Z80, 4=PCM, 5=PAT)
• BIOS_UPBANK equ $10FEDB ;byte: bank