gbdk-2020 | GameBoy Development Kit |
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gbdk-lib/libc/asm/z80/__uitobcd.s
1 ;--------------------------------------------------------------------------
2 ; __uitobcd.s
3 ;
4 ; Copyright (C) 2020, Sergey Belyashov
5 ;
6 ; This library is free software; you can redistribute it and/or modify it
7 ; under the terms of the GNU General Public License as published by the
8 ; Free Software Foundation; either version 2, or (at your option) any
9 ; later version.
10 ;
11 ; This library is distributed in the hope that it will be useful,
12 ; but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ; GNU General Public License for more details.
15 ;
16 ; You should have received a copy of the GNU General Public License
17 ; along with this library; see the file COPYING. If not, write to the
18 ; Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
19 ; MA 02110-1301, USA.
20 ;
21 ; As a special exception, if you link this library with other files,
22 ; some of which are compiled with SDCC, to produce an executable,
23 ; this library does not by itself cause the resulting executable to
24 ; be covered by the GNU General Public License. This exception does
25 ; not however invalidate any other reasons why the executable file
26 ; might be covered by the GNU General Public License.
27 ;--------------------------------------------------------------------------
28
29 .area _CODE
30
31 .globl ___uitobcd
32 ;
33 ; void __uitobcd (unsigned int v, unsigned char bcd[3])
34 ; __uitobcd converts v to BCD representation to the bcd.
35 ; bcd[] will contain BCD value.
36 ;
37 ___uitobcd:
38 push ix
39 ld ix, #0
40 add ix, sp
41 ;
42 ld bc, #0x1000
43 ld d, c
44 ld e, c
45 ld l, 4 (ix)
46 ld h, 5 (ix)
47 ;
48 ;--- begin speed optimization
49 ;
50 ld a, h
51 or a, a
52 jr NZ, 100$
53 ;
54 ld h, l
55 srl b
56 ;
57 ;--- end speed optimization
58 ;
59 ; HL - binary value
60 ; CDE - future BCD value
61 ; B - bits count (16)
62 100$:
63 add hl, hl
64 ld a, e
65 adc a, a
66 daa
67 ld e, a
68 ld a, d
69 adc a, a
70 daa
71 ld d, a
72 ld a, c
73 adc a, a
74 daa
75 ld c, a
76 djnz 100$
77 ;
78 ld l, 6 (ix)
79 ld h, 7 (ix)
80 ld (hl), e
81 inc hl
82 ld (hl), d
83 inc hl
84 ld (hl), c
85 ;
86 pop ix
87 ret
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