Difference between revisions of "USER subroutine"

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m (Command 2)
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==Command 2==
 
==Command 2==
 
Show demo.
 
Show demo.
Jump to [[SYSTEM_RETURN]] when finished.
 
  
 
==Command 3==
 
==Command 3==

Revision as of 19:18, 10 July 2013

The USER subroutine (not called, always jumped to by the BIOS) needs to perform actions according to the command value set in USER_REQUEST ( ) .

Command 0

Initilization of the soft/debug DIPs in the 68k user RAM. Used only once, when the game is started for the first time on a MVS system (probably when the BIOS doesn't find the game's NGH number in the backup RAM).

(The DIPs settings in RAM should then be copied to backup RAM by calling what function ?)

Initilization of the rest of the user RAM, the display, and I/O.

Viewpoint, which has its game save pointer set to $100000 (header $10E) and game save size set to $0200 (header $112) does this:

	move.b	#$00,BIOS_USER_MODE
	lea	$100000,a0		;Start of game save block
	move	#$001F,d1		;32*4 longword writes = 512 bytes
	moveq	#0,d0
.cl:
	move.l	d0,(a0)+
	move.l	d0,(a0)+
	move.l	d0,(a0)+
	move.l	d0,(a0)+
	dbf	d1,.cl
	move.b	d0,REG_WATCHDOG
...
        jmp     BIOSF_SYSTEM_RETURN

Command 1

Show the game's own boot logo animation (when $114 = 1).

Command 2

Show demo.

Command 3

Show title. BIOS_COMPULSION_TIMER ($10FDDA ) is used as a count-down timer.