1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
|
; something window scroll
Func_3e44:
push af
push hl
push bc
push de
ld hl, wd657
bit 0, [hl]
jr nz, .done
set 0, [hl]
ld b, $00
ld hl, wd658
ld c, [hl]
inc [hl]
ld hl, wd64b
add hl, bc
ld a, [hl]
ldh [rWX], a
ld hl, rLCDC
cp $a7
jr c, .disable_sprites
set 1, [hl] ; enable sprites
jr .asm_3e6c
.disable_sprites
res 1, [hl] ; disable sprites
.asm_3e6c
ld hl, wd651
add hl, bc
ld a, [hl]
cp $8f
jr c, .asm_3e9a
ld a, [wd665]
or a
jr z, .asm_3e93
ld hl, wd659
ld de, wd64b
ld bc, $6
call CopyDataHLtoDE
ld hl, wd65f
ld de, wd651
ld bc, $6
call CopyDataHLtoDE
.asm_3e93
xor a
ld [wd665], a
ld [wd658], a
.asm_3e9a
ldh [rLYC], a
ld hl, wd657
res 0, [hl]
.done
pop de
pop bc
pop hl
pop af
ret
; apply background scroll for lines 0 to 96 using the values at BGScrollData
; skip if wApplyBGScroll is non-0
ApplyBackgroundScroll:
push af
push hl
call DisableInt_LYCoincidence
ld hl, rSTAT
res STAT_LYCFLAG, [hl] ; reset coincidence flag
ei
ld hl, wApplyBGScroll
ld a, [hl]
or a
jr nz, .done
inc [hl]
push bc
push de
xor a
ld [wNextScrollLY], a
.ly_loop
ld a, [wNextScrollLY]
ld b, a
.wait_ly
ldh a, [rLY]
cp $60
jr nc, .ly_over_0x60
cp b ; already hit LY=b?
jr c, .wait_ly
call GetNextBackgroundScroll
ld hl, rSTAT
.wait_hblank_or_vblank
bit STAT_BUSY, [hl]
jr nz, .wait_hblank_or_vblank
ldh [rSCX], a
ldh a, [rLY]
inc a
ld [wNextScrollLY], a
jr .ly_loop
.ly_over_0x60
xor a
ldh [rSCX], a
ld a, $00
ldh [rLYC], a
call GetNextBackgroundScroll
ldh [hSCX], a
pop de
pop bc
xor a
ld [wApplyBGScroll], a
call EnableInt_LYCoincidence
.done
pop hl
pop af
ret
BGScrollData:
db 0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3
db 4, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 1, 1, 1, 0, 0
db 0, -1, -1, -1, -2, -2, -2, -3, -3, -3, -4, -4, -4, -4, -4, -4
db -5, -4, -4, -4, -4, -4, -4, -3, -3, -3, -2, -2, -2, -1, -1, -1
; 3f38
; x = BGScrollData[(wVBlankCounter + a) & $3f]
; return, in register a, x rotated right [wBGScrollMod]-1 times (max 3 times)
GetNextBackgroundScroll:
ld hl, wVBlankCounter
add [hl]
and $3f
ld c, a
ld b, $00
ld hl, BGScrollData
add hl, bc
ld a, [wBGScrollMod]
ld c, a
ld a, [hl]
dec c
jr z, .done
dec c
jr z, .halve
dec c
jr z, .quarter
; effectively zero
sra a
.quarter
sra a
.halve
sra a
.done
ret
; enable lcdc interrupt on LYC=LC coincidence
EnableInt_LYCoincidence:
push hl
ld hl, rSTAT
set STAT_LYC, [hl]
xor a
ld hl, rIE
set INT_LCD_STAT, [hl]
pop hl
ret
; disable lcdc interrupt and the LYC=LC coincidence trigger
DisableInt_LYCoincidence:
push hl
ld hl, rSTAT
res STAT_LYC, [hl]
xor a
ld hl, rIE
res INT_LCD_STAT, [hl]
pop hl
ret
|
