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
|
_Multiply: ; 37d41 (d:7d41)
ld a, $8
ld b, a
xor a
ld [H_PRODUCT], a ; $ff95
ld [H_MULTIPLYBUFFER], a ; $ff9b
ld [H_MULTIPLYBUFFER+1], a ; $ff9c
ld [H_MULTIPLYBUFFER+2], a ; $ff9d
ld [H_MULTIPLYBUFFER+3], a ; $ff9e
.multiplyLoop
ld a, [H_MULTIPLIER] ; $ff99
srl a
ld [H_MULTIPLIER], a ; $ff99
jr nc, .smallMultiplier ; less than $80
; code to possibly multiply the multiplicand by 2 and divide the multiplier by 2?
ld a, [H_MULTIPLYBUFFER+3]
ld c, a
ld a, [H_MULTIPLICAND+2]
add c
ld [H_MULTIPLYBUFFER+3], a
ld a, [H_MULTIPLYBUFFER+2]
ld c, a
ld a, [H_MULTIPLICAND+1]
adc c
ld [H_MULTIPLYBUFFER+2], a
ld a, [H_MULTIPLYBUFFER+1] ; $ff9c
ld c, a
ld a, [H_MULTIPLICAND] ; $ff96
adc c
ld [H_MULTIPLYDBUFFER+1], a ; $ff9c
ld a, [H_MULTIPLYBUFFER]
ld c, a
ld a, [H_PRODUCT] ; $ff95
adc c
ld [H_MULTIPLYBUFFER], a
.smallMultiplier
dec b
jr z, .done
ld a, [H_MULTIPLICAND]
sla a
ld [H_MULTIPLICAND+2], a
ld a, [H_MULTIPLICAND+1]
rl a
ld [H_MULTIPLICAND+1], a
ld a, [H_MULTIPLICAND] ; $ff96
rl a
ld [H_MULTIPLICAND], a ; $ff96
ld a, [H_PRODUCT] ; $ff95
rl a
ld [H_PRODUCT], a ; $ff95
jr .multiplyLoop
.done
ld a, [H_MULTIPLYBUFFER+3]
ld [H_PRODUCT+3], a
ld a, [H_MULTIPLYBUFFER+2]
ld [H_PRODUCT+2], a
ld a, [H_MULTIPLYBUFFER+1] ; $ff9c
ld [H_PRODUCT+1], a ; $ff96
ld [H_PRODUCT], a ; $ff95
ret
_Divide: ; 37da5 (d:7da5)
xor a
ld [H_DIVIDEBUFFER], a ; ff9a
ld [H_DIVIDEBUFFER+1], a ; ff9b
ld [H_DIVIDEBUFFER+2], a ; ff9c
ld [H_DIVIDEBUFFER+3], a ; ff9d
ld [H_DIVIDEBUFFER+4], a ; ff9e
ld a, $9
ld e, a
.asm_37db3
ld a, [H_DIVIDEBUFFER]
ld c, a
ld a, [H_DIVIDEND+1] ; $ff96
sub c
ld d, a
ld a, [H_DIVISOR] ; $ff99
ld c, a
ld a, [H_DIVIDEND] ; $ff95
sbc c
jr c, .asm_37dce
ld [H_DIVIDEND], a ; $ff95
ld a, d
ld [H_DIVIDEND+1], a ; $ff96
ld a, [H_DIVIDEBUFFER+4]
inc a
ld [H_DIVIDEBUFFER+4], a
jr .asm_37db3
.asm_37dce
ld a, b
cp $1
jr z, .done
ld a, [H_DIVIDEBUFFER+4]
sla a
ld [H_DIVIDEBUFFER+4], a
ld a, [H_DIVIDEBUFFER+3]
rl a
ld [H_DIVIDEBUFFER+3], a
ld a, [H_DIVIDEBUFFER+2] ; $ff9c
rl a
ld [H_DIVIDEBUFFER+2], a ; $ff9c
ld a, [H_DIVIDEBUFFER+1]
rl a
ld [H_DIVIDEBUFFER+1], a
dec e
jr nz, .asm_37e04
ld a, $8
ld e, a
ld a, [H_DIVIDEBUFFER]
ld [H_DIVISOR], a ; $ff99
xor a
ld [H_DIVIDEBUFFER], a
ld a, [H_DIVIDEND+1] ; $ff96
ld [H_DIVIDEND], a ; $ff95
ld a, [H_DIVIDEND+2]
ld [H_DIVIDEND+1], a ; $ff96
ld a, [H_DIVIDEND+3]
ld [H_DIVIDEND+2], a
.asm_37e04
ld a, e
cp $1
jr nz, .asm_37e0a
dec b
.asm_37e0a
ld a, [H_DIVIDEND+4] ; $ff99
srl a
ld [H_REMAINDER], a ; $ff99
ld a, [H_DIVIDEBUFFER]
rr a
ld [H_DIVIDEBUFFER], a
jr .asm_37db3
.done
ld a, [H_DIVIDEND+1] ; $ff96
ld [H_REMAINDER], a ; $ff99
ld a, [H_DIVIDEBUFFER+4]
ld [H_QUOTIENT+3], a
ld a, [H_DIVIDEBUFFER+3]
ld [H_QUOTIENT+2], a
ld a, [H_DIVIDEBUFFER+2] ; $ff9c
ld [H_QUOTIENT+1], a ; $ff96
ld a, [H_DIVIDEBUFFER+1]
ld [H_QUOTIENT], a ; $ff95
ret
|
