BIOS calls

Please see ASM Defines or C Defines for the hex addresses.

Simplify hierarchy and tell on which system each call works ?

Generic BIOS calls

BIOS calls common to every system.

BIOSF_VBL ($C0044A): Multiple purpose VBL routine

Sets values in RAM according to buttons states, checks CDDA commands, probably other things... Always (?) called each frame by games.

Memory locations set (all 8bit):

BIOS_P1CURRENT     $10FD95 Joystick 1 state
BIOS_P1PREVIOUS    $10FD96 Previous joystick 1 state
BIOS_P1CHANGE      $10FD97 Joystick 1 state change (edges)
BIOS_P1REPEAT      $10FD98 Joystick 1 repeat (edge, and strobe if held more than ? calls)

BIOS_P2CURRENT     $10FD9B Joystick 2 state
BIOS_P2PREVIOUS    $10FD9C Previous joystick 2 state
BIOS_P2CHANGE      $10FD9D Joystick 2 state change (edges)
BIOS_P2REPEAT      $10FD9E Joystick 2 repeat (edge, and strobe if held more than ? calls)

BIOS_STATCURNT     Joystick 1/2 start/select state
BIOS_STATCHANGE    Previous Joystick 1/2 start/select state

Bit definitions: see Joypad

AES/MVS BIOS calls

SP-E jump table:

Call address	Function
$C00402 to $C00432	Entry point
$C00438	Boot process
$C0043E to $C00462	?
$C00468	BIOSF_CRDACCESS
$C0046E	BIOSF_CRDREPORT
$C00474
$C0047A
$C00480 to $C004BC	RTS
$C004C2 to $C004D4	?

BIOSF_CRDACCESS ($C00468): Perform memory card operation

(Informations provided by User:Smkdan)

Memory locations used:

BIOS_CRDF       (8bit): function to perform when calling BIOSF_CRDACCESS, see below table
BIOS_CRDRESULT  (8bit): 00 on success, else 80+ and encodes the error, see below table
BIOS_CRDPTR     (32bit): pointer to read from/write to
BIOS_CRDSIZE    (16bit): how much data to read/write from/to card
BIOS_CRDNGH     (16bit): usually game [[NGH]].  Unique identifier for the game that 'owns' the save file
BIOS_CRDFILE    (16bit): each NGH has up to 16 save 'files' associated with

To access memory card, the RAM addresses above must be set depending on the function being attempted BIOS_CRDF values:

$00 (Format)

No extra parameters

$01 (Find)

In: BIOS_CRDNGH: NGH to find save files for

Out: BIOS_CRDFILE: 16bit mask containing 1 bits for each one of the 16 save files if present.

0 bits mean the save file is not present. i.e. FFFF = all 16 saves used, 8000 = only save file 15 is used

$02 (Load)

In:

CRDPTR: pointer to store loaded data to

CRDSIZE: the max size of data to load (automatically stops when entire file is loaded)

CRDNGH: NGH of file

CRDFILE: the file # of the given NGH to load from

$03 (Save)

In:

CRDPTR: pointer to read data to store to the card

CRDSIZE: size of data to save

CRDNGH: NGH of file

CRDFILE: the file # of the given NGH to save as

$04 (Delete)

In:

CRDNGH: NGH of file

CRDFILE: the file # of the given NGH to delete

$05 (GETNAME)

Gets name of a save file, forgot how these work...

$06 (SETUSER) (the username of the card)

$07 (GETUSER)

Errors may occur and the BIOS will store a value in BIOS_CRDRESULT depending on what went wrong:

• $00: no errors
• $80: no card inserted
• $81: card inserted, but not formatted
• $82: attempted to load a file that doesn't exist on the card
• $83: checksum error?
• $84: attempted to save to a full card
• $85: card write protect switch is active

CD BIOS calls

Same ones as the AES/MVS ?

BIOSF_UPLOAD ($C00546): Upload data to DRAM

BIOS_UPSRC      (32bit): Source (Long)
BIOS_UPDEST     (32bit): Destination (Long)
BIOS_UPSIZE     (32bit): Size (Long)
BIOS_UPZONE     (8bit):  Zone (Byte, 0=PRG, 1=FIX, 2=SPR, 3=Z80, 4=PCM, 5=PAT)
BIOS_UPBANK     (8bit):  Bank (Byte)

For FIX, Z80 (, PAT ?) and PCM upload, the destination has to be multiplied by 2 (8bit busses). The SPR bank size is 1MiB (4 banks), PCM bank size is 512KiB (4 banks). The other zones aren't banked.

BIOS_UPDEST (and BIOS_UPSRC ?) is incremented by the size upon completion, which allows to do multiple consecutive uploads.

BIOSF_LOADFILE ($C00552): Load file from CD (with animation)

A0 points to a file information block made of:

• The file name, ends with 0 (32 chars buffer ?)
• The destination bank (8bit)
• Eventual padding bytes to align the destination
• Destination (32bit)

Example (?): "STAGE_2.SPR",0x02,0x00,0x1600 loads STAGE_2.SPR at $201600 in the sprite DRAM.

For FIX, Z80 (, PAT ?) and PCM files, the destination is multiplied by 2 (8bit busses).

The destination memory is automatically chosen according to the file's extension.

BIOSF_CDDACMD ($C0056A): Issue CDDA command

Command/track pair in D0. Hooks the VBL interrupt for a while.

CDZ BIOS calls

Check track 0 ? Copy protection