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dc.l $0, start
dc.l empty_handler
dc.l empty_handler
;$10
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$20
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$30
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$40
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$50
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$60
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$70
dc.l int_4
dc.l empty_handler
dc.l int_6
dc.l empty_handler
;$80
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$90
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$A0
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$B0
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$C0
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$D0
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$E0
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
;$F0
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.l empty_handler
dc.b "SEGA GENESIS "
dc.b "(c) 2015.JULY "
dc.b "Menu "
dc.b " "
dc.b " "
dc.b "Menu "
dc.b " "
dc.b " "
dc.b "GM MK-00000-00", 0, 0
dc.b " "
dc.l $0, rom_end-1, $FF0000, $FFFFFF
dc.b " "
dc.b " "
dc.b " "
dc.b " "
dc.b "JUE "
;register addresses
VDP_DATA equ $C00000
VDP_CTRL equ $C00004
VDP_HV equ $C00008
Z80_RAM equ $A00000
IO_AREA equ $A10000
MODE_0 equ 0
MODE_1 equ 1
SCROLL_A equ 2
WINDOW equ 3
SCROLL_B equ 4
SAT equ 5
BG_COLOR equ 7
HINT equ $A
MODE_3 equ $B
MODE_4 equ $C
HSCROLL equ $D
AUTOINC equ $F
SCROLL EQU $10
WINDOW_H equ $11
WINDOW_V equ $12
DMALEN_L equ $13
DMALEN_H equ $14
DMASRC_L equ $15
DMASRC_M equ $16
DMASRC_H equ $17
VDP_VRAM_WRITE equ $40000000
VDP_CRAM_WRITE equ $C0000000
VDP_VSRAM_WRITE equ $40000010
VDP_DMA_FLAG equ $80
vdpregset macro
move.w #(((\1) << 8) | $8000 | (\2)), (a1)
endm
vdpreg macro
dc.w (((\1) << 8) | $8000 | (\2))
endm
;Writes a normal VDP command to the control port
;\1 - VDP address
;\2 - Access type
vdpaccess macro
move.l #((\2) | (\1) << 16 & $3FFF0000 | (\1) >> 14 & 3), (a1)
endm
empty_handler:
int_6:
rte
int_4:
rte
rsset $FFFF8000
x_pos rs.w 1
base_cmd rs.l 1
initial_regs:
vdpreg MODE_1, $4 ;Mode 5, everything turned off
vdpreg MODE_0, $4
vdpreg SCROLL_A, $20 ;Scroll a table $8000
vdpreg SCROLL_B, $05 ;Scroll b table $A000
vdpreg SAT, $60 ;SAT table $C000
vdpreg BG_COLOR, 0
vdpreg HINT, $FF
vdpreg MODE_3, 0 ;full screen scroll
vdpreg MODE_4, $87 ;40 cell mode, double-res interlace
vdpreg HSCROLL, 0
vdpreg AUTOINC, 2
vdpreg SCROLL, 1 ;64x32 scroll size
end_initial_regs
start:
lea $C00000, a0
lea $C00004, a1
moveq #(end_initial_regs-initial_regs-1), d0
lea initial_regs.w, a2
.regloop
move.w (a2)+, (a1)
dbra d0, .regloop
vdpaccess $0, VDP_CRAM_WRITE
move.w #$000, (a0)
move.w #$EEE, (a0)
;init scroll table
vdpaccess $0, VDP_VRAM_WRITE
move.w #0, (a0)
move.w #4, (a0)
;load tiles
vdpaccess $800, VDP_VRAM_WRITE
lea font(pc), a2
move.w #((fontend-font)/4 - 1), d0
tloop:
move.l (a2)+, (a0)
dbra d0, tloop
;clear name tables
vdpaccess $8000, VDP_VRAM_WRITE
moveq #32, d0
move.w #(64*64-1), d1
ploop:
move.l d0, (a0)
dbra d1, ploop
move.l #$40000002, d3
move.l d3, (a1)
move.l d3, base_cmd.w
lea Message(pc), a6
moveq #0, d0
bsr print_string
move.w #$8144, (a1) ;enable display
move #$2300, sr
wait_forever
stop #2500
bra wait_forever
Message:
dc.b "Journey From Darkness - Strider Returns (U) [c][!].bin", $A
dc.b "Toejam & Earl in Panic on Funkotron (U) [!].bin", $A
dc.b "Fire Shark (U) [c][!].bin", $A
dc.b "Sonic and Knuckles (W) [!].bin", 0
align 1
;Prints a null terminated string
;a6 - pointer to string
;a0 - VDP data port
;d0 - base tile attribute
;
;Clobbers: d1.w, d2.w, d3.l
print_string:
lea widths(pc), a5
move.w x_pos.w, d2
move.l base_cmd.w, d3
.loop
moveq #0, d1
move.b (a6)+, d1
beq .end
cmp.b #$A, d1
beq .newline
tst.b (-32, a5, d1.w)
beq .narrow
add.w d0, d1
move.w d1, (a0)
addq #2, d2
bra .loop
.narrow
add.w d0, d1
move.w d1, (a0)
addq #1, d2
move.l d2, d1
;switch to other plane
and.w #$FFFE, d1
swap d1
eor.l #$20000000, d3
or.l d3, d1
move.l d1, (a1)
bra .loop
.newline
moveq #0, d2
;switch back to plane A
and.l #$DFFFFFFF, d3
;skip to next row
add.l #$00800000, d3
move.l d3, (a1)
bra .loop
.end
move.w d2, x_pos.w
move.l d3, base_cmd.w
rts
align 1
font:
incbin font_interlace_variable.tiles
fontend
widths:
dc.b 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1
dc.b 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0
dc.b 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1
dc.b 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
dc.b 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1
rom_end:
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