BIOS RAM locations

Game Related

NeoCD top 3-2:

$10FDDC: 1=Load file with animation, 0=No animation

Address	DEF name	Size	Set by	Description
$10FD84~$10FD93	BIOS_GAME_DIP	16 bytes	BIOS	Software DIPs values
$10FDAE	BIOS_USER_REQUEST	byte	BIOS	Request for the USER subroutine. 0:Init, 1:Boot animation, 2:Demo, 3:Title
$10FDAF	BIOS_USER_MODE	byte	BIOS/Game	Used by the game to tell what it's doing: 0:Init/Boot animation, 1:Title/Demo, 2:Game Game selection can only be done on MVS systems when this byte is < 2
$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_MOD1	byte	Game	Sets player 1 status. 0:Never played, 1:Playing, 2:Continue option being displayed, 3:Game over
$10FDB7	BIOS_PLAYER_MOD2	byte	Game	Sets player 2 status. 0:Never played, 1:Playing, 2:Continue option being displayed, 3:Game over
$10FDB8	BIOS_PLAYER_MOD3	byte	Game	Sets player 3 status. 0:Never played, 1:Playing, 2:Continue option being displayed, 3:Game over
$10FDB9	BIOS_PLAYER_MOD4	byte	Game	Sets player 4 status. 0:Never played, 1:Playing, 2:Continue option being displayed, 3:Game over

System Related

Address	DEF name	Size	Set by	Description
$10FD80	BIOS_SYSTEM_MODE	byte	BIOS	0:BIOS wants vblank (system mode), $80:ok to use vblank (game mode)
$10FD81	BIOS_SYSRET_STATUS	byte	BIOS	Internal value that store the function code that SYSTEM_RETURN will call. 0 : init bram/select valid game for eye-catcher 1 : set the EL-LED to the correct value 2 : Switch to the next slot, relaunch eye-catcher 3 : After a gameover, save the playtime for bookeeping, switch to DEMO mode, reset the workbackup ram 4 : Switch next slot (select p1 pressed) 5 : Switch to previous slot (select p2 pressed) 6 : Called after a coin deposit, does nothing
$10FD82	BIOS_MVS_FLAG	byte	BIOS	0:AES, 1:MVS
$10FD83	BIOS_COUNTRY_CODE	byte	BIOS	0:Japan, 1:USA, 2:Europe
$10FE80	BIOS_DEVMODE	byte	BIOS/GAME	0 : Normal mode, 1 : Developer mode

Joypad Related

Updated by SYSTEM_IO

Address	DEF name	Size	Set by	Description
$10FD94	BIOS_P1STATUS	byte	BIOS	0:No connection, 1:Normal joypad, 2:Expanded joypad, 3:Mahjong controller, 4:Keyboard
$10FD95	BIOS_P1PREVIOUS	byte	BIOS	Previous frame DCBA Right Left Down Up (positive logic)
$10FD96	BIOS_P1CURRENT	byte	BIOS	Current frame DCBA Right Left Down Up (positive logic)
$10FD97	BIOS_P1CHANGE	byte	BIOS	Active edge DCBA Right Left Down Up (positive logic)
$10FD98	BIOS_P1REPEAT	byte	BIOS	Active edge + repeat every 8 frames after 16 frames. DCBA Right Left Down Up (positive logic)
$10FD99	BIOS_P1TIMER	byte	BIOS	Countdown ?
$10FD9A~$10FD9F	Same for P2	6 bytes	BIOS	See above
$10FDA0~$10FDA6	Same for P3	6 bytes	BIOS	See above
$10FDA7~$10FDAB	Same for P4	6 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) On MVS system the select bits are 0
$10FDAD	BIOS_STATCHANGE	byte	BIOS	Select P4, Start P4, Select P3, Start P3, Select P2, Start P2, Select P1, Start P1 (positive logic) On MVS system the select bits are 0
$10FEDC	BIOS_STATCURNT_RAW	byte	BIOS	Select P4, Start P4, Select P3, Start P3, Select P2, Start P2, Select P1, Start P1 (positive logic)
$10FEDD	BIOS_STATCHANGE_RAW	byte	BIOS	Select P4, Start P4, Select P3, Start P3, Select P2, Start P2, Select P1, Start P1 (positive logic)

Memory Card Related

See CARD for more explanation on those variables.

Address	DEF name	Size	Set by	Description
$10FDC4	BIOS_CARD_COMMAND	byte	BIOS or Game	Command to execute,
$10FDC6	BIOS_CARD_ANSWER	byte	BIOS	Answer code for the command
$10FDC8	BIOS_CARD_START	longword	BIOS or Game	Pointer to data
$10FDCC	BIOS_CARD_SIZE	word	BIOS or Game	Size of data
$10FDCE	BIOS_CARD_FCB	word	BIOS or Game	Game NGH number
$10FDD0	BIOS_CARD_SUB	byte or word	BIOS or Game	Game Subnumber

MESS OUT Related

See MESS_OUT to know how to use this routine.

Address	DEF name	Size	Set by	Description
$10FDBE	BIOS_MESS_POINT	longword	Game	buffer pointer
$10FDC2	BIOS_MESS_BUSY	byte	Game	0:Allow MESS_OUT, 1:Skip MESS_OUT

Calendar Related

Those value are updated when READ_CALENDAR is called

Address	DEF name	Size	Set by	Description
$10FDD2	BIOS_YEAR	byte	BIOS	Current year
$10FDD3	BIOS_MONTH	byte	BIOS	Current month
$10FDD4	BIOS_DAY	byte	BIOS	Current day
$10FDD5	BIOS_WEEKDAY	byte	BIOS	Current weekday (Sunday = 00, Monday = 01 ... Saturday = 06)
$10FDD6	BIOS_HOUR	byte	BIOS	Current hour (24h format)
$10FDD7	BIOS_MINUTE	byte	BIOS	Current minute
$10FDD8	BIOS_SECOND	byte	BIOS	Current minute

BIOS internal

Address	DEF name	Size	Set by	Description
$10FCEF	BIOS_SLOTCHECK	byte	BIOS	Slot check passed if non-zero
$10FDDA	BIOS_COMPULSION_TIMER	byte	BIOS	Timer for the game compulsion start feature, in seconds.
$10FDDB	BIOS_COMPULSION_FRAME_TIMER	byte	BIOS	Frame based timer for the game compulsion start feature. When reach 0, timer is reseted to $3B and START_COMPULSION_TIMER is decremented.
$10FE88	BIOS_FRAME_COUNTER	longword	BIOS	Frame counter, updated by SYSTEM_IO
$10FEBF	BIOS_BRAM_USED	byte	BIOS	0 : BRAM not currently used, 1 : Currently used
$10FEE1	BIOS_FRAME_SKIP	byte	BIOS	Number of frame to skip the routine which check the demo_end or if the player have pressed start Decremented in SYSTEM_IO
$10FEE3	BIOS_INT1_SKIP	byte	BIOS	Only used in SYSTEM_INT1, if set to 0 it will call MESS_OUT and SYSTEM_IO.
$10FEE4	BIOS_INT1_FRAME_COUNTER	byte	BIOS	Frame counter, only used in SYSTEM_INT1

4P mode related

Thoses will be valid on a 4P compatible bios only

Address	DEF name	Size	Set by	Description
$10FEF8	BIOS_4P_REQUESTED	byte	BIOS	Keeps a local copy of hard dip 2 status on bootup. 0: dip2 wasn't set $2: dip 2 was on.
$10FEFA	BIOS_4P_MODE	byte	BIOS	Main 4P flag, is set when hard dip 2 is on and 4P board is found. 0: regular play $FF: 4P mode game
$10FEFB	BIOS_4P_PLUGGED	byte	BIOS	0: 4P board not found $FF: 4P board plugged 4P compatible bios will check for 4P board regardless of dip2 switch status.

Other

Address	DEF name	Size	Set by	Description
$10FCEE	?	byte	GAME	Z80/M ROM check pass

; 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, 7=OBJ, 8=A** files)
*BIOS_UPBANK     equ $10FEDB ;byte: bank