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jalmah.x68: Commentary (nw)

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angelosa 2018-06-17 03:20:03 +02:00
parent a845a6c4fa
commit e4e7a4780c
1 changed files with 32 additions and 34 deletions
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66
src/mame/etc/jalmah.x68
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@ -14,64 +14,61 @@
START:
ORG $0 ; palette code snippet (test mode & gameplay)
move.w #$1, $80016.l ; set priority number (for urashima)
move.w #$f, D0
move.w #$f, D0 ; set loop 1
FetchNewPalette:
move.l A0, $100400.l
movea.l (A0), A0
move.w #$f, D1
bsr UploadPaletteChunk
movea.l $100400.l, A0
move.l A0, $100400.l ; save address to our local buffer (address currently points to an index of actual palette to transfer)
movea.l (A0), A0 ; read ROM location for the actual palette source
move.w #$f, D1 ; set loop 2 variable
bsr UploadPaletteChunk ; jump to uploading routine
movea.l $100400.l, A0 ; restore address index, increment by next address
adda.w #$4, A0
dbra D0, FetchNewPalette
rts
UploadPaletteChunk:
move.w (A0)+, (A1)+
move.w (A0)+, (A1)+ ; copy palette source in ROM to palette RAM
dbra D1, UploadPaletteChunk
rts
ORG $0800 ; sound code snippet
; move.w #$0, $8001a.l
; move.w $f0b80.l, $80018.l
; move.w $100ffc.l, $80018.l
; move.w $100ffe.l, $8001a.l
movem.l D1, -(A7)
move.w D0, D1
ror.w #$8, D1
and.w #$f, D1
movem.l D1, -(A7)
move.w D0, D1 ; D0 is raw sound command, low byte is command number, everything else is banking and probably voice channel (unhandled)
ror.w #$8, D1
and.w #$f, D1 ; take D1 as raw banking number
bsr CheckSoundZA
bsr CheckSoundBank
move.w #$8, $80040.l
move.w #$8, $80040.l ; clear channel
bsr SoundStatus
andi.w #$3f, D0
andi.w #$3f, D0 ; take command number and write it to OKI port
ori.w #$80, D0
move.w D0, $80040.l
bsr SoundStatus
move.w #$10, $80040.l
move.w #$10, $80040.l ; play channel
movem.l (A7)+, D1
rts
SoundStatus:
movem.l D0, -(A7)
movem.l D0, -(A7)
ReadStatus:
move.w $80040.l, D0
move.w $80040.l, D0 ; check OKI voice status
andi.w #$1,D0
bne ReadStatus
movem.l (A7)+, D0
rts
; guess: special bits set in register D0 affect banking (oki can play up to 64 samples so bits 6 and 7 cannot be used)
; we simulate "ZA" writing but use the other bank register (jalmah can do both, cfr. ports $80018 and $8001a
CheckSoundZA:
btst #$6, D0 ;urashima BGM at start of game
btst #$6, D0 ; urashima BGM at start of game
beq NoZA1
ror.w #$1, D1
ror.w #$1, D1 ; shift one down
rts
NoZA1:
btst #$07, D0 ;mjzoomin BGM at start of game
btst #$07, D0 ; mjzoomin BGM at start of game
beq NoZA2
move.w #$8, D1
move.w #$8, D1 ; hardcode to bank 3
NoZA2:
rts
CheckSoundBank:
cmpi.w #$1, D1
cmpi.w #$1, D1 ; verify our raw D1 and set base bank accordingly
beq SetBank0
cmpi.w #$2, D1
beq SetBank1
@ -91,29 +88,29 @@ SetBank2:
ORG $1000 ; tile upload snippet
TileUploadStart:
move.w (A2)+, (A1)+
move.w (A2)+, (A1)+ ; just take A2 source (tiles) to A1 destination VRAM
dbra D0, TileUploadStart
rts
ORG $1800 ; (another) palette code snippet
movem.l D0-D7/A1-A6, -(A7) ; save stack (A0 intentionally updated by this snippet)
move.w #$f, D0
move.w #$f, D0 ; what's the difference here? Same as above but no hardcoded priority?
bsr FetchNewPalette
movem.l (A7)+, D0-D7/A1-A6
rts
ORG $2000 ; daireikai RNG snippet (guess)
move.w D5, $100400.l
move.w $f000c.l, D5
add.l D6, D5
move.w $f000c.l, D5 ; take current RNG number
add.l D6, D5 ; add D6
andi.w #$3f, D5
move.w D5, $f000c.l
move.w D5, $f000c.l ; round it
move.w $100400.l, D5
rts
ORG $2800 ; daireikai layer clearances
movem.l D0-D7/A0-A6, -(A7)
lea $90000.l, A6
move.w #$1fff, D1
lea $90000.l, A6 ; layer 0
move.w #$1fff, D1
move.w #$00ff, D0
bsr ClearLayer
movem.l (A7)+, D0-D7/A0-A6
@ -124,7 +121,7 @@ ClearLayer:
rts
ORG $2880
movem.l D0-D7/A0-A6, -(A7)
lea $94000.l, A6
lea $94000.l, A6 ; layer 1
move.w #$1fff, D1
move.w #$00ff, D0
bsr ClearLayer
@ -132,7 +129,7 @@ ClearLayer:
rts
ORG $2900
movem.l D0-D7/A0-A6, -(A7)
lea $98000.l, A6
lea $98000.l, A6 ; layer 2
move.w #$1fff, D1
move.w #$f0ff, D0
bsr ClearLayer
@ -143,6 +140,7 @@ ClearLayer:
dc.w $ffff
END START
*~Font name~Courier New~
*~Font size~10~
*~Tab type~1~