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main.asm
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; =========================================================================
; | Sonic the Hedgehog Disassembly for Sega Mega Drive |
; =========================================================================
;
; Disassembly created by Hivebrain
; thanks to drx, Stealth and Esrael L.G. Neto
; ===========================================================================
include "constants.asm"
include "variables.asm"
include "macros.asm"
EnableSRAM: equ 0 ; change to 1 to enable SRAM
BackupSRAM: equ 1
AddressSRAM: equ 3 ; 0 = odd+even; 2 = even only; 3 = odd only
Revision: equ 0 ; change to 1 for JP1 revision
ZoneCount: equ 6 ; discrete zones are: GHZ, MZ, SYZ, LZ, SLZ, and SBZ
OptimiseSound: equ 0 ; change to 1 to optimise sound queuing
; ===========================================================================
StartOfRom:
Vectors: dc.l $FFFE00, EntryPoint, BusError, AddressError
dc.l IllegalInstr, ZeroDivide, ChkInstr, TrapvInstr
dc.l PrivilegeViol, Trace, Line1010Emu, Line1111Emu
dc.l ErrorExcept, ErrorExcept, ErrorExcept, ErrorExcept
dc.l ErrorExcept, ErrorExcept, ErrorExcept, ErrorExcept
dc.l ErrorExcept, ErrorExcept, ErrorExcept, ErrorExcept
dc.l ErrorExcept, ErrorTrap, ErrorTrap, ErrorTrap
dc.l HBlank, ErrorTrap, VBlank, ErrorTrap
dc.l ErrorTrap, ErrorTrap, ErrorTrap, ErrorTrap
dc.l ErrorTrap, ErrorTrap, ErrorTrap, ErrorTrap
dc.l ErrorTrap, ErrorTrap, ErrorTrap, ErrorTrap
dc.l ErrorTrap, ErrorTrap, ErrorTrap, ErrorTrap
dc.l ErrorTrap, ErrorTrap, ErrorTrap, ErrorTrap
dc.l ErrorTrap, ErrorTrap, ErrorTrap, ErrorTrap
dc.l ErrorTrap, ErrorTrap, ErrorTrap, ErrorTrap
dc.l ErrorTrap, ErrorTrap, ErrorTrap, ErrorTrap
Console: dc.b "SEGA MEGA DRIVE " ; Hardware system ID
Date: dc.b "(C)SEGA 1991.APR" ; Release date
Title_Local: dc.b "SONIC THE HEDGEHOG " ; Domestic name
Title_Int: dc.b "SONIC THE HEDGEHOG " ; International name
Serial: if Revision=0
dc.b "GM 00001009-00" ; Serial/version number
else
dc.b "GM 00004049-01"
endc
Checksum: dc.w 0
dc.b "J " ; I/O support
RomStartLoc: dc.l StartOfRom ; ROM start
RomEndLoc: dc.l EndOfRom-1 ; ROM end
RamStartLoc: dc.l $FF0000 ; RAM start
RamEndLoc: dc.l $FFFFFF ; RAM end
SRAMSupport: if EnableSRAM=1
dc.b $52, $41, $A0+(BackupSRAM<<6)+(AddressSRAM<<3), $20
else
dc.l $20202020
endc
dc.l $20202020 ; SRAM start ($200001)
dc.l $20202020 ; SRAM end ($20xxxx)
Notes: dc.b " "
Region: dc.b "JUE " ; Region
; ===========================================================================
ErrorTrap:
nop
nop
bra.s ErrorTrap
; ===========================================================================
EntryPoint:
tst.l (z80_port_1_control).l ; test port A & B control registers
bne.s PortA_Ok
tst.w (z80_expansion_control).l ; test port C control register
PortA_Ok:
bne.s SkipSetup
lea SetupValues(pc),a5
movem.w (a5)+,d5-d7
movem.l (a5)+,a0-a4
move.b -$10FF(a1),d0 ; get hardware version (from $A10001)
andi.b #$F,d0
beq.s SkipSecurity
move.l #'SEGA',$2F00(a1) ; move "SEGA" to TMSS register ($A14000)
SkipSecurity:
move.w (a4),d0
moveq #0,d0
movea.l d0,a6
move.l a6,usp ; set usp to 0
moveq #$17,d1
VDPInitLoop:
move.b (a5)+,d5 ; add $8000 to value
move.w d5,(a4) ; move value to VDP register
add.w d7,d5 ; next register
dbf d1,VDPInitLoop
move.l (a5)+,(a4)
move.w d0,(a3) ; clear the VRAM
move.w d7,(a1) ; stop the Z80
move.w d7,(a2) ; reset the Z80
WaitForZ80:
btst d0,(a1) ; has the Z80 stopped?
bne.s WaitForZ80 ; if not, branch
moveq #$25,d2
Z80InitLoop:
move.b (a5)+,(a0)+
dbf d2,Z80InitLoop
move.w d0,(a2)
move.w d0,(a1) ; start the Z80
move.w d7,(a2) ; reset the Z80
ClrRAMLoop:
move.l d0,-(a6)
dbf d6,ClrRAMLoop ; clear the entire RAM
move.l (a5)+,(a4) ; set VDP display mode and increment
move.l (a5)+,(a4) ; set VDP to CRAM write
moveq #$1F,d3
ClrCRAMLoop:
move.l d0,(a3)
dbf d3,ClrCRAMLoop ; clear the CRAM
move.l (a5)+,(a4)
moveq #$13,d4
ClrVSRAMLoop:
move.l d0,(a3)
dbf d4,ClrVSRAMLoop ; clear the VSRAM
moveq #3,d5
PSGInitLoop:
move.b (a5)+,$11(a3) ; reset the PSG
dbf d5,PSGInitLoop
move.w d0,(a2)
movem.l (a6),d0-a6 ; clear all registers
disable_ints
SkipSetup:
bra.s GameProgram ; begin game
; ===========================================================================
SetupValues: dc.w $8000 ; VDP register start number
dc.w $3FFF ; size of RAM/4
dc.w $100 ; VDP register diff
dc.l z80_ram ; start of Z80 RAM
dc.l z80_bus_request ; Z80 bus request
dc.l z80_reset ; Z80 reset
dc.l vdp_data_port ; VDP data
dc.l vdp_control_port ; VDP control
dc.b 4 ; VDP $80 - 8-colour mode
dc.b $14 ; VDP $81 - Megadrive mode, DMA enable
dc.b ($C000>>10) ; VDP $82 - foreground nametable address
dc.b ($F000>>10) ; VDP $83 - window nametable address
dc.b ($E000>>13) ; VDP $84 - background nametable address
dc.b ($D800>>9) ; VDP $85 - sprite table address
dc.b 0 ; VDP $86 - unused
dc.b 0 ; VDP $87 - background colour
dc.b 0 ; VDP $88 - unused
dc.b 0 ; VDP $89 - unused
dc.b 255 ; VDP $8A - HBlank register
dc.b 0 ; VDP $8B - full screen scroll
dc.b $81 ; VDP $8C - 40 cell display
dc.b ($DC00>>10) ; VDP $8D - hscroll table address
dc.b 0 ; VDP $8E - unused
dc.b 1 ; VDP $8F - VDP increment
dc.b 1 ; VDP $90 - 64 cell hscroll size
dc.b 0 ; VDP $91 - window h position
dc.b 0 ; VDP $92 - window v position
dc.w $FFFF ; VDP $93/94 - DMA length
dc.w 0 ; VDP $95/96 - DMA source
dc.b $80 ; VDP $97 - DMA fill VRAM
dc.l $40000080 ; VRAM address 0
dc.b $AF ; xor a
dc.b $01, $D9, $1F ; ld bc,1fd9h
dc.b $11, $27, $00 ; ld de,0027h
dc.b $21, $26, $00 ; ld hl,0026h
dc.b $F9 ; ld sp,hl
dc.b $77 ; ld (hl),a
dc.b $ED, $B0 ; ldir
dc.b $DD, $E1 ; pop ix
dc.b $FD, $E1 ; pop iy
dc.b $ED, $47 ; ld i,a
dc.b $ED, $4F ; ld r,a
dc.b $D1 ; pop de
dc.b $E1 ; pop hl
dc.b $F1 ; pop af
dc.b $08 ; ex af,af'
dc.b $D9 ; exx
dc.b $C1 ; pop bc
dc.b $D1 ; pop de
dc.b $E1 ; pop hl
dc.b $F1 ; pop af
dc.b $F9 ; ld sp,hl
dc.b $F3 ; di
dc.b $ED, $56 ; im1
dc.b $36, $E9 ; ld (hl),e9h
dc.b $E9 ; jp (hl)
dc.w $8104 ; VDP display mode
dc.w $8F02 ; VDP increment
dc.l $C0000000 ; CRAM write mode
dc.l $40000010 ; VSRAM address 0
dc.b $9F, $BF, $DF, $FF ; values for PSG channel volumes
; ===========================================================================
GameProgram:
tst.w (vdp_control_port).l
btst #6,($A1000D).l
beq.s CheckSumCheck
cmpi.l #'init',(v_init).w ; has checksum routine already run?
beq.w GameInit ; if yes, branch
CheckSumCheck:
movea.l #ErrorTrap,a0 ; start checking bytes after the header ($200)
movea.l #RomEndLoc,a1 ; stop at end of ROM
move.l (a1),d0
moveq #0,d1
@loop:
add.w (a0)+,d1
cmp.l a0,d0
bhs.s @loop
movea.l #Checksum,a1 ; read the checksum
cmp.w (a1),d1 ; compare checksum in header to ROM
bne.w CheckSumError ; if they don't match, branch
CheckSumOk:
lea ($FFFFFE00).w,a6
moveq #0,d7
move.w #$7F,d6
@clearRAM:
move.l d7,(a6)+
dbf d6,@clearRAM ; clear RAM ($FE00-$FFFF)
move.b (z80_version).l,d0
andi.b #$C0,d0
move.b d0,(v_megadrive).w ; get region setting
move.l #'init',(v_init).w ; set flag so checksum won't run again
GameInit:
lea ($FF0000).l,a6
moveq #0,d7
move.w #$3F7F,d6
@clearRAM:
move.l d7,(a6)+
dbf d6,@clearRAM ; clear RAM ($0000-$FDFF)
bsr.w VDPSetupGame
bsr.w SoundDriverLoad
bsr.w JoypadInit
move.b #id_Sega,(v_gamemode).w ; set Game Mode to Sega Screen
MainGameLoop:
move.b (v_gamemode).w,d0 ; load Game Mode
andi.w #$1C,d0
jsr GameModeArray(pc,d0.w) ; jump to apt location in ROM
bra.s MainGameLoop
; ===========================================================================
; ---------------------------------------------------------------------------
; Main game mode array
; ---------------------------------------------------------------------------
GameModeArray:
ptr_GM_Sega: bra.w GM_Sega ; Sega Screen ($00)
ptr_GM_Title: bra.w GM_Title ; Title Screen ($04)
ptr_GM_Demo: bra.w GM_Level ; Demo Mode ($08)
ptr_GM_Level: bra.w GM_Level ; Normal Level ($0C)
ptr_GM_Special: bra.w GM_Special ; Special Stage ($10)
ptr_GM_Cont: bra.w GM_Continue ; Continue Screen ($14)
ptr_GM_Ending: bra.w GM_Ending ; End of game sequence ($18)
ptr_GM_Credits: bra.w GM_Credits ; Credits ($1C)
rts
; ===========================================================================
CheckSumError:
bsr.w VDPSetupGame
move.l #$C0000000,(vdp_control_port).l ; set VDP to CRAM write
moveq #$3F,d7
@fillred:
move.w #cRed,(vdp_data_port).l ; fill palette with red
dbf d7,@fillred ; repeat $3F more times
@endlessloop:
bra.s @endlessloop
; ===========================================================================
BusError:
move.b #2,(v_errortype).w
bra.s loc_43A
AddressError:
move.b #4,(v_errortype).w
bra.s loc_43A
IllegalInstr:
move.b #6,(v_errortype).w
addq.l #2,2(sp)
bra.s loc_462
ZeroDivide:
move.b #8,(v_errortype).w
bra.s loc_462
ChkInstr:
move.b #$A,(v_errortype).w
bra.s loc_462
TrapvInstr:
move.b #$C,(v_errortype).w
bra.s loc_462
PrivilegeViol:
move.b #$E,(v_errortype).w
bra.s loc_462
Trace:
move.b #$10,(v_errortype).w
bra.s loc_462
Line1010Emu:
move.b #$12,(v_errortype).w
addq.l #2,2(sp)
bra.s loc_462
Line1111Emu:
move.b #$14,(v_errortype).w
addq.l #2,2(sp)
bra.s loc_462
ErrorExcept:
move.b #0,(v_errortype).w
bra.s loc_462
; ===========================================================================
loc_43A:
disable_ints
addq.w #2,sp
move.l (sp)+,(v_spbuffer).w
addq.w #2,sp
movem.l d0-a7,(v_regbuffer).w
bsr.w ShowErrorMessage
move.l 2(sp),d0
bsr.w ShowErrorValue
move.l (v_spbuffer).w,d0
bsr.w ShowErrorValue
bra.s loc_478
; ===========================================================================
loc_462:
disable_ints
movem.l d0-a7,(v_regbuffer).w
bsr.w ShowErrorMessage
move.l 2(sp),d0
bsr.w ShowErrorValue
loc_478:
bsr.w ErrorWaitForC
movem.l (v_regbuffer).w,d0-a7
enable_ints
rte
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
ShowErrorMessage:
lea (vdp_data_port).l,a6
locVRAM $F800
lea (Art_Text).l,a0
move.w #$27F,d1
@loadgfx:
move.w (a0)+,(a6)
dbf d1,@loadgfx
moveq #0,d0 ; clear d0
move.b (v_errortype).w,d0 ; load error code
move.w ErrorText(pc,d0.w),d0
lea ErrorText(pc,d0.w),a0
locVRAM (vram_fg+$604)
moveq #$12,d1 ; number of characters (minus 1)
@showchars:
moveq #0,d0
move.b (a0)+,d0
addi.w #$790,d0
move.w d0,(a6)
dbf d1,@showchars ; repeat for number of characters
rts
; End of function ShowErrorMessage
; ===========================================================================
ErrorText: dc.w @exception-ErrorText, @bus-ErrorText
dc.w @address-ErrorText, @illinstruct-ErrorText
dc.w @zerodivide-ErrorText, @chkinstruct-ErrorText
dc.w @trapv-ErrorText, @privilege-ErrorText
dc.w @trace-ErrorText, @line1010-ErrorText
dc.w @line1111-ErrorText
@exception: dc.b "ERROR EXCEPTION "
@bus: dc.b "BUS ERROR "
@address: dc.b "ADDRESS ERROR "
@illinstruct: dc.b "ILLEGAL INSTRUCTION"
@zerodivide: dc.b "@ERO DIVIDE "
@chkinstruct: dc.b "CHK INSTRUCTION "
@trapv: dc.b "TRAPV INSTRUCTION "
@privilege: dc.b "PRIVILEGE VIOLATION"
@trace: dc.b "TRACE "
@line1010: dc.b "LINE 1010 EMULATOR "
@line1111: dc.b "LINE 1111 EMULATOR "
even
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
ShowErrorValue:
move.w #$7CA,(a6) ; display "$" symbol
moveq #7,d2
@loop:
rol.l #4,d0
bsr.s @shownumber ; display 8 numbers
dbf d2,@loop
rts
; End of function ShowErrorValue
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
@shownumber:
move.w d0,d1
andi.w #$F,d1
cmpi.w #$A,d1
blo.s @chars0to9
addq.w #7,d1 ; add 7 for characters A-F
@chars0to9:
addi.w #$7C0,d1
move.w d1,(a6)
rts
; End of function sub_5CA
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
ErrorWaitForC:
bsr.w ReadJoypads
cmpi.b #btnC,(v_jpadpress1).w ; is button C pressed?
bne.w ErrorWaitForC ; if not, branch
rts
; End of function ErrorWaitForC
; ===========================================================================
Art_Text: incbin "graphics\uncompressed\menutext.bin" ; text used in level select and debug mode
even
; ===========================================================================
; ---------------------------------------------------------------------------
; Vertical interrupt
; ---------------------------------------------------------------------------
VBlank:
movem.l d0-a6,-(sp)
tst.b (v_vbla_routine).w
beq.s VBla_00
move.w (vdp_control_port).l,d0
move.l #$40000010,(vdp_control_port).l
move.l (v_scrposy_dup).w,(vdp_data_port).l ; send screen y-axis pos. to VSRAM
btst #6,(v_megadrive).w ; is Megadrive PAL?
beq.s @notPAL ; if not, branch
move.w #$700,d0
@waitPAL:
dbf d0,@waitPAL
@notPAL:
move.b (v_vbla_routine).w,d0
move.b #0,(v_vbla_routine).w
move.w #1,(f_hbla_pal).w
andi.w #$3E,d0
move.w VBla_Index(pc,d0.w),d0
jsr VBla_Index(pc,d0.w)
VBla_Music:
jsr (UpdateMusic).l
VBla_Exit:
addq.l #1,(v_vbla_count).w
movem.l (sp)+,d0-a6
rte
; ===========================================================================
VBla_Index: dc.w VBla_00-VBla_Index, VBla_02-VBla_Index
dc.w VBla_04-VBla_Index, VBla_06-VBla_Index
dc.w VBla_08-VBla_Index, VBla_0A-VBla_Index
dc.w VBla_0C-VBla_Index, VBla_0E-VBla_Index
dc.w VBla_10-VBla_Index, VBla_12-VBla_Index
dc.w VBla_14-VBla_Index, VBla_16-VBla_Index
dc.w VBla_0C-VBla_Index
; ===========================================================================
VBla_00:
cmpi.b #$80+id_Level,(v_gamemode).w
beq.s @islevel
cmpi.b #id_Level,(v_gamemode).w ; is game on a level?
bne.w VBla_Music ; if not, branch
@islevel:
cmpi.b #id_LZ,(v_zone).w ; is level LZ ?
bne.w VBla_Music ; if not, branch
move.w (vdp_control_port).l,d0
btst #6,(v_megadrive).w ; is Megadrive PAL?
beq.s @notPAL ; if not, branch
move.w #$700,d0
@waitPAL:
dbf d0,@waitPAL
@notPAL:
move.w #1,(f_hbla_pal).w ; set HBlank flag
stopZ80
waitZ80
tst.b (f_wtr_state).w ; is water above top of screen?
bne.s @waterabove ; if yes, branch
writeCRAM v_pal_dry,$80,0
bra.s @waterbelow
@waterabove:
writeCRAM v_pal_water,$80,0
@waterbelow:
move.w (v_hbla_hreg).w,(a5)
startZ80
bra.w VBla_Music
; ===========================================================================
VBla_02:
bsr.w sub_106E
VBla_14:
tst.w (v_demolength).w
beq.w @end
subq.w #1,(v_demolength).w
@end:
rts
; ===========================================================================
VBla_04:
bsr.w sub_106E
bsr.w sub_6886
bsr.w sub_1642
tst.w (v_demolength).w
beq.w @end
subq.w #1,(v_demolength).w
@end:
rts
; ===========================================================================
VBla_06:
bsr.w sub_106E
rts
; ===========================================================================
VBla_10:
cmpi.b #id_Special,(v_gamemode).w ; is game on special stage?
beq.w VBla_0A ; if yes, branch
VBla_08:
stopZ80
waitZ80
bsr.w ReadJoypads
tst.b (f_wtr_state).w
bne.s @waterabove
writeCRAM v_pal_dry,$80,0
bra.s @waterbelow
@waterabove:
writeCRAM v_pal_water,$80,0
@waterbelow:
move.w (v_hbla_hreg).w,(a5)
writeVRAM v_hscrolltablebuffer,$380,vram_hscroll
writeVRAM v_spritetablebuffer,$280,vram_sprites
tst.b (f_sonframechg).w ; has Sonic's sprite changed?
beq.s @nochg ; if not, branch
writeVRAM v_sgfx_buffer,$2E0,vram_sonic ; load new Sonic gfx
move.b #0,(f_sonframechg).w
@nochg:
startZ80
movem.l (v_screenposx).w,d0-d7
movem.l d0-d7,($FFFFFF10).w
movem.l (v_bgscroll1).w,d0-d1
movem.l d0-d1,($FFFFFF30).w
cmpi.b #96,(v_hbla_line).w
bhs.s Demo_Time
move.b #1,($FFFFF64F).w
addq.l #4,sp
bra.w VBla_Exit
; ---------------------------------------------------------------------------
; Subroutine to run a demo for an amount of time
; ---------------------------------------------------------------------------
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
Demo_Time:
bsr.w LoadTilesAsYouMove
jsr (AnimateLevelGfx).l
jsr (HUD_Update).l
bsr.w sub_165E
tst.w (v_demolength).w ; is there time left on the demo?
beq.w @end ; if not, branch
subq.w #1,(v_demolength).w ; subtract 1 from time left
@end:
rts
; End of function Demo_Time
; ===========================================================================
VBla_0A:
stopZ80
waitZ80
bsr.w ReadJoypads
writeCRAM v_pal_dry,$80,0
writeVRAM v_spritetablebuffer,$280,vram_sprites
writeVRAM v_hscrolltablebuffer,$380,vram_hscroll
startZ80
bsr.w PalCycle_SS
tst.b (f_sonframechg).w ; has Sonic's sprite changed?
beq.s @nochg ; if not, branch
writeVRAM v_sgfx_buffer,$2E0,vram_sonic ; load new Sonic gfx
move.b #0,(f_sonframechg).w
@nochg:
tst.w (v_demolength).w
beq.w @end
subq.w #1,(v_demolength).w
@end:
rts
; ===========================================================================
VBla_0C:
stopZ80
waitZ80
bsr.w ReadJoypads
tst.b (f_wtr_state).w
bne.s @waterabove
writeCRAM v_pal_dry,$80,0
bra.s @waterbelow
@waterabove:
writeCRAM v_pal_water,$80,0
@waterbelow:
move.w (v_hbla_hreg).w,(a5)
writeVRAM v_hscrolltablebuffer,$380,vram_hscroll
writeVRAM v_spritetablebuffer,$280,vram_sprites
tst.b (f_sonframechg).w
beq.s @nochg
writeVRAM v_sgfx_buffer,$2E0,vram_sonic
move.b #0,(f_sonframechg).w
@nochg:
startZ80
movem.l (v_screenposx).w,d0-d7
movem.l d0-d7,($FFFFFF10).w
movem.l (v_bgscroll1).w,d0-d1
movem.l d0-d1,($FFFFFF30).w
bsr.w LoadTilesAsYouMove
jsr (AnimateLevelGfx).l
jsr (HUD_Update).l
bsr.w sub_1642
rts
; ===========================================================================
VBla_0E:
bsr.w sub_106E
addq.b #1,($FFFFF628).w
move.b #$E,(v_vbla_routine).w
rts
; ===========================================================================
VBla_12:
bsr.w sub_106E
move.w (v_hbla_hreg).w,(a5)
bra.w sub_1642
; ===========================================================================
VBla_16:
stopZ80
waitZ80
bsr.w ReadJoypads
writeCRAM v_pal_dry,$80,0
writeVRAM v_spritetablebuffer,$280,vram_sprites
writeVRAM v_hscrolltablebuffer,$380,vram_hscroll
startZ80
tst.b (f_sonframechg).w
beq.s @nochg
writeVRAM v_sgfx_buffer,$2E0,vram_sonic
move.b #0,(f_sonframechg).w
@nochg:
tst.w (v_demolength).w
beq.w @end
subq.w #1,(v_demolength).w
@end:
rts
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
sub_106E:
stopZ80
waitZ80
bsr.w ReadJoypads
tst.b (f_wtr_state).w ; is water above top of screen?
bne.s @waterabove ; if yes, branch
writeCRAM v_pal_dry,$80,0
bra.s @waterbelow
@waterabove:
writeCRAM v_pal_water,$80,0
@waterbelow:
writeVRAM v_spritetablebuffer,$280,vram_sprites
writeVRAM v_hscrolltablebuffer,$380,vram_hscroll
startZ80
rts
; End of function sub_106E
; ---------------------------------------------------------------------------
; Horizontal interrupt
; ---------------------------------------------------------------------------
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
HBlank:
disable_ints
tst.w (f_hbla_pal).w ; is palette set to change?
beq.s @nochg ; if not, branch
move.w #0,(f_hbla_pal).w
movem.l a0-a1,-(sp)
lea (vdp_data_port).l,a1
lea (v_pal_water).w,a0 ; get palette from RAM
move.l #$C0000000,4(a1) ; set VDP to CRAM write
move.l (a0)+,(a1) ; move palette to CRAM
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.l (a0)+,(a1)
move.w #$8A00+223,4(a1) ; reset HBlank register
movem.l (sp)+,a0-a1
tst.b ($FFFFF64F).w
bne.s loc_119E
@nochg:
rte
; ===========================================================================
loc_119E:
clr.b ($FFFFF64F).w
movem.l d0-a6,-(sp)
bsr.w Demo_Time
jsr (UpdateMusic).l
movem.l (sp)+,d0-a6
rte
; End of function HBlank
; ---------------------------------------------------------------------------
; Subroutine to initialise joypads
; ---------------------------------------------------------------------------
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
JoypadInit:
stopZ80
waitZ80
moveq #$40,d0
move.b d0,($A10009).l ; init port 1 (joypad 1)
move.b d0,($A1000B).l ; init port 2 (joypad 2)
move.b d0,($A1000D).l ; init port 3 (expansion)
startZ80
rts
; End of function JoypadInit
; ---------------------------------------------------------------------------
; Subroutine to read joypad input, and send it to the RAM
; ---------------------------------------------------------------------------
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
ReadJoypads:
lea (v_jpadhold1).w,a0 ; address where joypad states are written
lea ($A10003).l,a1 ; first joypad port
bsr.s @read ; do the first joypad
addq.w #2,a1 ; do the second joypad
@read:
move.b #0,(a1)
nop
nop
move.b (a1),d0
lsl.b #2,d0
andi.b #$C0,d0
move.b #$40,(a1)
nop
nop
move.b (a1),d1
andi.b #$3F,d1
or.b d1,d0
not.b d0
move.b (a0),d1
eor.b d0,d1
move.b d0,(a0)+
and.b d0,d1
move.b d1,(a0)+
rts
; End of function ReadJoypads
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
VDPSetupGame:
lea (vdp_control_port).l,a0
lea (vdp_data_port).l,a1
lea (VDPSetupArray).l,a2
moveq #$12,d7
@setreg:
move.w (a2)+,(a0)
dbf d7,@setreg ; set the VDP registers
move.w (VDPSetupArray+2).l,d0
move.w d0,(v_vdp_buffer1).w
move.w #$8A00+223,(v_hbla_hreg).w
moveq #0,d0
move.l #$C0000000,(vdp_control_port).l ; set VDP to CRAM write
move.w #$3F,d7
@clrCRAM:
move.w d0,(a1)
dbf d7,@clrCRAM ; clear the CRAM
clr.l (v_scrposy_dup).w
clr.l (v_scrposx_dup).w
move.l d1,-(sp)
fillVRAM 0,$FFFF,0
@waitforDMA:
move.w (a5),d1
btst #1,d1 ; is DMA (fillVRAM) still running?
bne.s @waitforDMA ; if yes, branch
move.w #$8F02,(a5) ; set VDP increment size
move.l (sp)+,d1
rts
; End of function VDPSetupGame
; ===========================================================================
VDPSetupArray: dc.w $8004 ; 8-colour mode
dc.w $8134 ; enable V.interrupts, enable DMA
dc.w $8200+(vram_fg>>10) ; set foreground nametable address
dc.w $8300+($A000>>10) ; set window nametable address
dc.w $8400+(vram_bg>>13) ; set background nametable address
dc.w $8500+(vram_sprites>>9) ; set sprite table address
dc.w $8600 ; unused
dc.w $8700 ; set background colour (palette entry 0)
dc.w $8800 ; unused
dc.w $8900 ; unused
dc.w $8A00 ; default H.interrupt register
dc.w $8B00 ; full-screen vertical scrolling
dc.w $8C81 ; 40-cell display mode
dc.w $8D00+(vram_hscroll>>10) ; set background hscroll address
dc.w $8E00 ; unused
dc.w $8F02 ; set VDP increment size
dc.w $9001 ; 64-cell hscroll size
dc.w $9100 ; window horizontal position
dc.w $9200 ; window vertical position
; ---------------------------------------------------------------------------
; Subroutine to clear the screen
; ---------------------------------------------------------------------------
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
ClearScreen:
fillVRAM 0,$FFF,vram_fg ; clear foreground namespace
@wait1:
move.w (a5),d1
btst #1,d1
bne.s @wait1
move.w #$8F02,(a5)
fillVRAM 0,$FFF,vram_bg ; clear background namespace
@wait2:
move.w (a5),d1
btst #1,d1
bne.s @wait2
move.w #$8F02,(a5)
if Revision=0
move.l #0,(v_scrposy_dup).w
move.l #0,(v_scrposx_dup).w
else
clr.l (v_scrposy_dup).w
clr.l (v_scrposx_dup).w
endc
lea (v_spritetablebuffer).w,a1
moveq #0,d0
move.w #($280/4),d1 ; This should be ($280/4)-1, leading to a slight bug (first bit of v_pal_water is cleared)
@clearsprites:
move.l d0,(a1)+
dbf d1,@clearsprites ; clear sprite table (in RAM)
lea (v_hscrolltablebuffer).w,a1
moveq #0,d0
move.w #($400/4),d1 ; This should be ($400/4)-1, leading to a slight bug (first bit of the Sonic object's RAM is cleared)
@clearhscroll:
move.l d0,(a1)+
dbf d1,@clearhscroll ; clear hscroll table (in RAM)
rts
; End of function ClearScreen
; ---------------------------------------------------------------------------
; Subroutine to load the sound driver
; ---------------------------------------------------------------------------
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||