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sonic.asm
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sonic.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
; ===========================================================================
cpu 68000
EnableSRAM = 0 ; change to 1 to enable SRAM
BackupSRAM = 1
AddressSRAM = 3 ; 0 = odd+even; 2 = even only; 3 = odd only
; Change to 0 to build the original version of the game, dubbed REV00
; Change to 1 to build the later vesion, dubbed REV01, which includes various bugfixes and enhancements
; Change to 2 to build the version from Sonic Mega Collection, dubbed REVXB, which fixes the infamous "spike bug"
Revision = 1
ZoneCount = 6 ; discrete zones are: GHZ, MZ, SYZ, LZ, SLZ, and SBZ
FixBugs = 0 ; change to 1 to enable bugfixes
zeroOffsetOptimization = 0 ; if 1, makes a handful of zero-offset instructions smaller
include "MacroSetup.asm"
include "Constants.asm"
include "Variables.asm"
include "Macros.asm"
; ===========================================================================
StartOfRom:
Vectors: dc.l v_systemstack&$FFFFFF ; Initial stack pointer value
dc.l EntryPoint ; Start of program
dc.l BusError ; Bus error
dc.l AddressError ; Address error (4)
dc.l IllegalInstr ; Illegal instruction
dc.l ZeroDivide ; Division by zero
dc.l ChkInstr ; CHK exception
dc.l TrapvInstr ; TRAPV exception (8)
dc.l PrivilegeViol ; Privilege violation
dc.l Trace ; TRACE exception
dc.l Line1010Emu ; Line-A emulator
dc.l Line1111Emu ; Line-F emulator (12)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved) (16)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved) (20)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved)
dc.l ErrorExcept ; Unused (reserved) (24)
dc.l ErrorExcept ; Spurious exception
dc.l ErrorTrap ; IRQ level 1
dc.l ErrorTrap ; IRQ level 2
dc.l ErrorTrap ; IRQ level 3 (28)
dc.l HBlank ; IRQ level 4 (horizontal retrace interrupt)
dc.l ErrorTrap ; IRQ level 5
dc.l VBlank ; IRQ level 6 (vertical retrace interrupt)
dc.l ErrorTrap ; IRQ level 7 (32)
dc.l ErrorTrap ; TRAP #00 exception
dc.l ErrorTrap ; TRAP #01 exception
dc.l ErrorTrap ; TRAP #02 exception
dc.l ErrorTrap ; TRAP #03 exception (36)
dc.l ErrorTrap ; TRAP #04 exception
dc.l ErrorTrap ; TRAP #05 exception
dc.l ErrorTrap ; TRAP #06 exception
dc.l ErrorTrap ; TRAP #07 exception (40)
dc.l ErrorTrap ; TRAP #08 exception
dc.l ErrorTrap ; TRAP #09 exception
dc.l ErrorTrap ; TRAP #10 exception
dc.l ErrorTrap ; TRAP #11 exception (44)
dc.l ErrorTrap ; TRAP #12 exception
dc.l ErrorTrap ; TRAP #13 exception
dc.l ErrorTrap ; TRAP #14 exception
dc.l ErrorTrap ; TRAP #15 exception (48)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
if Revision<>2
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
dc.l ErrorTrap ; Unused (reserved)
else
loc_E0:
; Relocated code from Spik_Hurt. REVXB was a nasty hex-edit.
move.l obY(a0),d3
move.w obVelY(a0),d0
ext.l d0
asl.l #8,d0
jmp (loc_D5A2).l
dc.w ErrorTrap
dc.l ErrorTrap
dc.l ErrorTrap
dc.l ErrorTrap
endif
dc.b "SEGA MEGA DRIVE " ; Hardware system ID (Console name)
dc.b "(C)SEGA 1991.APR" ; Copyright holder and release date (generally year)
dc.b "SONIC THE HEDGEHOG " ; Domestic name
dc.b "SONIC THE HEDGEHOG " ; International name
if Revision=0
dc.b "GM 00001009-00" ; Serial/version number (Rev 0)
else
dc.b "GM 00004049-01" ; Serial/version number (Rev non-0)
endif
Checksum:
if Revision=0
dc.w $264A ; Hardcoded to make it easier to check for ROM correctness
else
dc.w $AFC7
endif
dc.b "J " ; I/O support
dc.l StartOfRom ; Start address of ROM
RomEndLoc: dc.l EndOfRom-1 ; End address of ROM
dc.l $FF0000 ; Start address of RAM
dc.l $FFFFFF ; End address of RAM
if EnableSRAM=1
dc.b $52, $41, $A0+(BackupSRAM<<6)+(AddressSRAM<<3), $20 ; SRAM support
else
dc.l $20202020
endif
dc.l $20202020 ; SRAM start ($200001)
dc.l $20202020 ; SRAM end ($20xxxx)
dc.b " " ; Notes (unused, anything can be put in this space, but it has to be 52 bytes.)
dc.b "JUE " ; Region (Country code)
EndOfHeader:
; ===========================================================================
; Crash/Freeze the 68000. Unlike Sonic 2, Sonic 1 uses the 68000 for playing music, so it stops too
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 ; Skip the VDP and Z80 setup code if port A, B or C is ok...?
lea SetupValues(pc),a5 ; Load setup values array address.
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 ; If the console has no TMSS, skip the security stuff.
move.l #'SEGA',$2F00(a1) ; move "SEGA" to TMSS register ($A14000)
SkipSecurity:
move.w (a4),d0 ; clear write-pending flag in VDP to prevent issues if the 68k has been reset in the middle of writing a command long word to the VDP.
moveq #0,d0 ; clear d0
movea.l d0,a6 ; clear 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) ; clear 4 bytes of RAM
dbf d6,ClrRAMLoop ; repeat until the entire RAM is clear
move.l (a5)+,(a4) ; set VDP display mode and increment mode
move.l (a5)+,(a4) ; set VDP to CRAM write
moveq #$1F,d3 ; set repeat times
ClrCRAMLoop:
move.l d0,(a3) ; clear 2 palettes
dbf d3,ClrCRAMLoop ; repeat until the entire CRAM is clear
move.l (a5)+,(a4) ; set VDP to VSRAM write
moveq #$13,d4
ClrVSRAMLoop:
move.l d0,(a3) ; clear 4 bytes of VSRAM.
dbf d4,ClrVSRAMLoop ; repeat until the entire VSRAM is clear
moveq #3,d5
PSGInitLoop:
move.b (a5)+,$11(a3) ; reset the PSG
dbf d5,PSGInitLoop ; repeat for other channels
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
; Z80 instructions (not the sound driver; that gets loaded later)
if (*)+$26 < $10000
save
CPU Z80 ; start assembling Z80 code
phase 0 ; pretend we're at address 0
xor a ; clear a to 0
ld bc,((z80_ram_end-z80_ram)-zStartupCodeEndLoc)-1 ; prepare to loop this many times
ld de,zStartupCodeEndLoc+1 ; initial destination address
ld hl,zStartupCodeEndLoc ; initial source address
ld sp,hl ; set the address the stack starts at
ld (hl),a ; set first byte of the stack to 0
ldir ; loop to fill the stack (entire remaining available Z80 RAM) with 0
pop ix ; clear ix
pop iy ; clear iy
ld i,a ; clear i
ld r,a ; clear r
pop de ; clear de
pop hl ; clear hl
pop af ; clear af
ex af,af' ; swap af with af'
exx ; swap bc/de/hl with their shadow registers too
pop bc ; clear bc
pop de ; clear de
pop hl ; clear hl
pop af ; clear af
ld sp,hl ; clear sp
di ; clear iff1 (for interrupt handler)
im 1 ; interrupt handling mode = 1
ld (hl),0E9h ; replace the first instruction with a jump to itself
jp (hl) ; jump to the first instruction (to stay there forever)
zStartupCodeEndLoc:
dephase ; stop pretending
restore
padding off ; unfortunately our flags got reset so we have to set them again...
else ; due to an address range limitation I could work around but don't think is worth doing so:
message "Warning: using pre-assembled Z80 startup code."
dc.w $AF01,$D91F,$1127,$0021,$2600,$F977,$EDB0,$DDE1,$FDE1,$ED47,$ED4F,$D1E1,$F108,$D9C1,$D1E1,$F1F9,$F3ED,$5636,$E9E9
endif
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,(z80_expansion_control+1).l
beq.s CheckSumCheck
cmpi.l #'init',(v_init).w ; has checksum routine already run?
beq.w GameInit ; if yes, branch
CheckSumCheck:
movea.l #EndOfHeader,a0 ; start checking bytes after the header ($200)
movea.l #RomEndLoc,a1 ; stop at end of ROM
move.l (a1),d0
moveq #0,d1
.loop:
add.w (a0)+,d1
cmp.l a0,d0
bhs.s .loop
movea.l #Checksum,a1 ; read the checksum
cmp.w (a1),d1 ; compare checksum in header to ROM
bne.w CheckSumError ; if they don't match, branch
CheckSumOk:
lea (v_crossresetram).w,a6
moveq #0,d7
move.w #(v_ram_end-v_crossresetram)/4-1,d6
.clearRAM:
move.l d7,(a6)+
dbf d6,.clearRAM ; clear RAM ($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 (v_ram_start&$FFFFFF).l,a6
moveq #0,d7
move.w #(v_crossresetram-v_ram_start)/4-1,d6
.clearRAM:
move.l d7,(a6)+
dbf d6,.clearRAM ; clear RAM ($0000-$FDFF)
bsr.w VDPSetupGame
bsr.w DACDriverLoad
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 ; limit Game Mode value to $1C max (change to a maximum of 7C to add more game modes)
jsr GameModeArray(pc,d0.w) ; jump to apt location in ROM
bra.s MainGameLoop ; loop indefinitely
; ===========================================================================
; ---------------------------------------------------------------------------
; 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: binclude "artunc/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_vdp).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 ; wait here in a loop doing nothing for a while...
.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 LoadTilesAsYouMove_BGOnly
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,ArtTile_Sonic*$20 ; load new Sonic gfx
move.b #0,(f_sonframechg).w
.nochg:
startZ80
movem.l (v_screenposx).w,d0-d7
movem.l d0-d7,(v_screenposx_dup).w
movem.l (v_fg_scroll_flags).w,d0-d1
movem.l d0-d1,(v_fg_scroll_flags_dup).w
cmpi.b #96,(v_hbla_line).w
bhs.s Demo_Time
move.b #1,(f_doupdatesinhblank).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 ProcessDPLC2
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,ArtTile_Sonic*$20 ; load new Sonic gfx
move.b #0,(f_sonframechg).w
.nochg:
tst.w (v_demolength).w ; is there time left on the demo?
beq.w .end ; if not, return
subq.w #1,(v_demolength).w ; subtract 1 from time left in demo
.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,ArtTile_Sonic*$20
move.b #0,(f_sonframechg).w
.nochg:
startZ80
movem.l (v_screenposx).w,d0-d7
movem.l d0-d7,(v_screenposx_dup).w
movem.l (v_fg_scroll_flags).w,d0-d1
movem.l d0-d1,(v_fg_scroll_flags_dup).w
bsr.w LoadTilesAsYouMove
jsr (AnimateLevelGfx).l
jsr (HUD_Update).l
bsr.w sub_1642
rts
; ===========================================================================
VBla_0E:
bsr.w sub_106E
addq.b #1,(v_vbla_0e_counter).w ; Unused besides this one write...
move.b #$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,ArtTile_Sonic*$20
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 (f_doupdatesinhblank).w
bne.s loc_119E
.nochg:
rte
; ===========================================================================
loc_119E:
clr.b (f_doupdatesinhblank).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 #$40,d0
move.b d0,(z80_port_1_control+1).l ; init port 1 (joypad 1)
move.b d0,(z80_port_2_control+1).l ; init port 2 (joypad 2)
move.b d0,(z80_expansion_control+1).l ; init port 3 (expansion/extra)
startZ80
rts
; End of function JoypadInit
; ---------------------------------------------------------------------------
; Subroutine to read joypad input, and send it to the RAM
; ---------------------------------------------------------------------------
; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
ReadJoypads:
lea (v_jpadhold1).w,a0 ; address where joypad states are written
lea (z80_port_1_data+1).l,a1 ; first joypad port
bsr.s .read ; do the first joypad
addq.w #2,a1 ; do the second joypad
.read:
move.b #0,(a1)
nop
nop
move.b (a1),d0
lsl.b #2,d0
andi.b #$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 #$8A00+223,(v_hbla_hreg).w ; H-INT every 224th scanline
moveq #0,d0
move.l #$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