Sega Genesis coding template by drx (In the article)

Sonic2771 @DOUBLENET

4 years ago

Sega Genesis coding template by drx

(In the article)

Vectors: dc.l $FFFE00, Entrypoint, Error, Error

dc.l Error, Error, Error, Error

dc.l HBlank, Error, VBlank, Error

dc.l Error, Error, Error, Error

Header: dc.b 'SEGA MEGA DRIVE ' ; Console name

dc.b '(C) DRX 2004.NOV' ; Copyright/Date

DomesticName: dc.b 'Code template by drx - www.hacking-cult.org ' ; Domestic Name

dc.b 'Code template by drx - www.hacking-cult.org ' ; International Name

dc.b 'GM 00000000-00' ; Version

Checksum: dc.w $1337

; Checksum

dc.b 'J ' ; I/O Support

RomStartLoc: dc.l 0 ; ROM Start

RomEndLoc: dc.l RomEnd

; ROM End

RamStartLoc: dc.l $FF0000 ; RAM Start

RamEndLoc: dc.l $FFFFFF ; RAM End

dc.b $20,$20,$20,$20 ; 'RA',$F8,$20 if SRAM = on

SramStart: dc.l $20202020 ; $200000 if SRAM = on

SramEnd: dc.l $20202020 ; $20xxxx if SRAM = on

dc.b ' ' ; Notes

dc.b ' '

dc.b 'JUE ' ; Country

;---------------------

; Code start

;---------------------

Entrypoint:

tst.l ($A10008).l ;Test Port A control

bne PortA_Ok

tst.w ($A1000C).l ;Test Port C control

PortA_Ok:

bne SkipSetup

move.b ($A10001).l,d0 ;version

andi.b #$F,d0

beq SkipSecurity ;if the smd/gen model is 1, skip the security

move.l #'SEGA',($A14000).l

SkipSecurity:

move.w ($C00004).l,d0 ;test if VDP works

moveq #0,d0

movea.l d0,a6

move a6,usp ;set usp to $0

;---------------------

; Setup VDP registers

;---------------------

lea (VDPSetupArray),a0

move.w #(VDPSetupArrayEnd-VDPSetupArray)/2,d1 ;$18 VDP registers

VDPSetupLoop:

move.w (a0)+,($C00004).l

dbf d1,VDPSetupLoop

move.l #$40000080,($C00004).l

move.w #0,($C00000).l ;clean the screen

;---------------------

; Init the Z80

;---------------------

move.w #$100,($A11100).l ;Stop the Z80

move.w #$100,($A11200).l ;Reset the Z80

Waitforz80:

btst #0,($A11100).l

bne Waitforz80 ;Wait for z80 to halt

lea (Z80Init),a0

lea ($A00000).l,a1

move.w #Z80InitEnd-Z80Init,d1

InitZ80:

move.b (a0)+,(a1)+

dbf d1,InitZ80

move.w #0,($A11200).l

move.w #0,($A11100).l ;Start the Z80

move.w #$100,($A11200).l

;---------------------

; Reset the RAM

;---------------------

lea ($FFFF0000).l,a0

move.w #$3fff,d1

ClearRAM:

move.l #0,(a0)+

dbf d1,ClearRAM

;---------------------

; VDP again

;---------------------

move.w #$8174,($C00004).l

move.w #$8F02,($C00004).l

;---------------------

; Clear the CRAM

;---------------------

move.l #$C0000000,($C00004).l ;Set VDP ctrl to CRAM write

move.w #$3f,d1

ClearCRAM:

move.w #0,($C00000).l

dbf d1,ClearCRAM

;---------------------

; Clear the VDP stuff

;---------------------

move.l #$40000010,($C00004).l

move.w #$13,d1

ClearStuff:

move.l #0,($C00000).l

dbf d1,ClearStuff

;---------------------

; Init the PSG

;---------------------

move.b #$9F,($C00011).l

move.b #$BF,($C00011).l

move.b #$DF,($C00011).l

move.b #$FF,($C00011).l

move.w #0,($A11200).l

;---------------------

; Load the z80 driver

;---------------------

move.w #$100,($A11100).l ;Stop the Z80

move.w #$100,($A11200).l ;Reset the Z80

Waitforz80a:

btst #0,($A11100).l

bne Waitforz80a ;Wait for z80 to halt

lea (Z80Driver),a0

lea ($A00000).l,a1

move.W #Z80DriverEnd-Z80Driver,d1

LoadZ80Driver:

move.b (a0)+,(a1)+

dbf d1,LoadZ80Driver

move.w #0,($A11100).l ;Start the Z80

;---------------------

; Clear the registers

; and set the SR

;---------------------

movem.l ($FF0000).l,d0-a6

lea ($FFFE00).l,a7

move #$2700,sr

SkipSetup:

;-----------------------

; Here starts your code

;-----------------------

Main:

rts

;---------------------

; Error exceptions

;---------------------

Error:

rte

;---------------------

; Horizontal Blank

;---------------------

HBlank:

rte

;---------------------

; Vertical Blank

;---------------------

VBlank:

rte

;---------------------

; VDP registers array

;---------------------

VDPSetupArray:

dc.w $8004 ;9-bit palette = 1 (otherwise would be 3-bit), HBlank = 0

dc.w $8134 ;Genesis display = 1, DMA = 1, VBlank = 1, display = 0

dc.w $8230 ;Scroll A - $C000

dc.w $8338 ;Window - $E000

dc.w $8407 ;Scroll B - $E000

dc.w $857c ;Sprites - $F800

dc.w $8600 ;Unused

dc.w $8700 ;Backdrop color - $00

dc.w $8800 ;Unused

dc.w $8900 ;Unused

dc.w $8A00 ;H Interrupt register

dc.w $8B00 ;Full screen scroll, no external interrupts

dc.w $8C81 ;40 cells display

dc.w $8D3F ;H Scroll - $FC00

dc.w $8E00 ;Unused

dc.w $8F02 ;VDP auto increment

dc.w $9001 ;64 cells scroll

dc.w $9100 ;Window H position

dc.w $9200 ;Window V position

dc.w $93FF ;DMA stuff (off)

dc.w $94FF ;DMA stuff (off)

dc.w $9500 ;DMA stuff (off)

dc.w $9600 ;DMA stuff (off)

dc.w $9780 ;DMA stuff (off)

VDPSetupArrayEnd:

;---------------------

; Z80 init code

;---------------------

Z80Init:

dc.w $af01, $d91f, $1127, $0021, $2600, $f977

dc.w $edb0, $dde1, $fde1, $ed47, $ed4f, $d1e1

dc.w $f108, $d9c1, $d1e1, $f1f9, $f3ed, $5636

dc.w $e9e9

Z80InitEnd:

;---------------------

; Music driver (z80)

;---------------------

Z80Driver:

dc.b $c3,$46,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00

dc.b $00,$00,$00,$00,$00,$f3,$ed,$56,$31,$00,$20,$3a,$39,$00,$b7,$ca,$4c,$00,$21,$3a,$00,$11,$40,$00,$01,$06,$00,$ed,$b0,$3e,$00,$32,$39,$00,$3e,$b4,$32,$02,$40,$3e,$c0,$32,$03,$40,$3e,$2b,$32,$00,$40,$3e,$80,$32,$01,$40,$3a,$43,$00,$4f,$3a,$44,$00,$47,$3e,$06,$3d

dc.b $c2,$81,$00,$21,$00,$60,$3a,$41,$00,$07,$77,$3a,$42,$00,$77,$0f,$77,$0f,$77,$0f,$77,$0f,$77,$0f,$77,$0f,$77,$0f,$77,$3a,$40,$00,$6f,$3a,$41,$00,$f6,$80,$67,$3e,$2a,$32,$00,$40,$7e,$32,$01,$40,$21,$40,$00,$7e,$c6,$01,$77,$23,$7e,$ce,$00,$77,$23,$7e,$ce,$00,$77

dc.b $3a,$39,$00,$b7,$c2,$4c,$00,$0b,$78,$b1,$c2,$7f,$00,$3a,$45,$00,$b7,$ca,$4c,$00,$3d,$3a,$45,$00,$06,$ff,$0e,$ff,$c3,$7f,$00

Z80DriverEnd:

RomEnd:

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