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|
SECTION "main",rom0
; set up stack
ld sp,$fffe
; clear vram ($8000–9fff)
xor a
ld hl,$9fff
vloop:
ld [hld],a
bit 7,h
jr nz,vloop
; set up audio
ld hl,$ff26
ld c,$11
ld a,$80
ld [hld],a
ld [$ff00+c],a
inc c
ld a,$f3
ld [$ff00+c],a
ld [hld],a
ld a,$77
ld [hl],a
; set background palette
ld a,%11111100
ld [$ff47],a
; convert and load logo data from cart into vram
ld de,$0104
ld hl,$8010
lloop:
ld a,[de]
call Graphics
call Graphics2
inc de
ld a,e
cp $34
jr nz,lloop
; load 8 additional bytes into vram
ld de,registered
ld b,registered_ - registered
eloop:
ld a,[de]
inc de
ld [hli],a
inc hl
dec b
jr nz,eloop
; set background tilemap
ld a,$19
ld [$9910],a
ld hl,$992f
oloop:
ld c,$0c
iloop:
dec a
jr z,scroll
ld [hld],a
dec c
jr nz,iloop
ld l,$f
jr oloop
scroll:
; initialize scroll count
ld h,a
; set loop count and vertical scroll register
ld a,$64
ld d,a
ld [$ff42],a
; turn on lcd (showing background)
ld a,$91
ld [$ff40],a
inc b
sloop:
ld e,2
floop1:
ld c,$c
floop2:
ld a,[$ff44]
cp $90 ; wait for screen frame
jr nz,floop2
dec c
jr nz,floop2
dec e
jr nz,floop1
ld c,$13
inc h ; increment scroll count
ld a,h
ld e,$83
cp $62 ; 62 counts in, play sound #1
jr z,sound1
ld e,$c1
cp $64
jr nz,sound2 ; 64 counts in, play sound #2
sound1:
ld a,e
ld [$ff00+c],a
inc c
ld a,$87
ld [$ff00+c],a
sound2:
ld a,[$ff42]
sub b
ld [$ff42],a ; scroll logo up if b=1
dec d
jr nz,sloop
dec b ; set b=0 first time
jr nz,logocheck ; … next time, cause jump to logo check
ld d,$20 ; use scrolling loop to pause
jr sloop
Graphics:
ld c,a ; “double up” all the bits of the graphics data, store it in vram
Graphics2:
ld b,4
dloop:
push bc
rl c
rla
pop bc
rl c
rla
dec b
jr nz,dloop
ld [hli],a
inc hl
ld [hli],a
inc hl
ret
logo:
INCLUDE "nintendo.s"
registered:
INCBIN "®.bin"
registered_:
logocheck:
ld hl,$0104 ; cart logo
ld de,logo
lastbranch:
ld a,[de]
inc de
cp [hl] ; compare cart logo to bootrom logo
llockup:
jr nz,llockup
inc hl
ld a,l
cp $34
jr nz,lastbranch
ld b,$19
ld a,b
cloop:
add [hl]
inc hl
dec b
jr nz,cloop
add [hl]
clockup:
jr nz,clockup
ld a,1
ld [$ff50],a ; turn off bootrom
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