1 // ---------------------------------------------------------------------------
2 // This file is part of reSID, a MOS6581 SID emulator engine.
3 // Copyright (C) 2002 Dag Lem <resid@nimrod.no>
4 //
5 // This program is free software; you can redistribute it and/or modify
6 // it under the terms of the GNU General Public License as published by
7 // the Free Software Foundation; either version 2 of the License, or
8 // (at your option) any later version.
9 //
10 // This program is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 // GNU General Public License for more details.
14 //
15 // You should have received a copy of the GNU General Public License
16 // along with this program; if not, write to the Free Software
17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 // ---------------------------------------------------------------------------
19
20 #define __WAVE_CC__
21 #include "wave.h"
22
23 RESID_NAMESPACE_START
24
25 // ----------------------------------------------------------------------------
26 // Constructor.
27 // ----------------------------------------------------------------------------
WaveformGenerator()28 WaveformGenerator::WaveformGenerator()
29 {
30 sync_source = this;
31
32 set_chip_model(MOS6581);
33
34 reset();
35 }
36
37
38 // ----------------------------------------------------------------------------
39 // Set sync source.
40 // ----------------------------------------------------------------------------
set_sync_source(WaveformGenerator * source)41 void WaveformGenerator::set_sync_source(WaveformGenerator* source)
42 {
43 sync_source = source;
44 source->sync_dest = this;
45 }
46
47
48 // ----------------------------------------------------------------------------
49 // Set chip model.
50 // ----------------------------------------------------------------------------
set_chip_model(chip_model model)51 void WaveformGenerator::set_chip_model(chip_model model)
52 {
53 if (model == MOS6581) {
54 wave__ST = wave6581__ST;
55 wave_P_T = wave6581_P_T;
56 wave_PS_ = wave6581_PS_;
57 wave_PST = wave6581_PST;
58 }
59 else {
60 wave__ST = wave8580__ST;
61 wave_P_T = wave8580_P_T;
62 wave_PS_ = wave8580_PS_;
63 wave_PST = wave8580_PST;
64 }
65 }
66
67
68 // ----------------------------------------------------------------------------
69 // Register functions.
70 // ----------------------------------------------------------------------------
writeFREQ_LO(reg8 freq_lo)71 void WaveformGenerator::writeFREQ_LO(reg8 freq_lo)
72 {
73 freq = freq & 0xff00 | freq_lo & 0x00ff;
74 }
75
writeFREQ_HI(reg8 freq_hi)76 void WaveformGenerator::writeFREQ_HI(reg8 freq_hi)
77 {
78 freq = (freq_hi << 8) & 0xff00 | freq & 0x00ff;
79 }
80
writePW_LO(reg8 pw_lo)81 void WaveformGenerator::writePW_LO(reg8 pw_lo)
82 {
83 pw = pw & 0xf00 | pw_lo & 0x0ff;
84 }
85
writePW_HI(reg8 pw_hi)86 void WaveformGenerator::writePW_HI(reg8 pw_hi)
87 {
88 pw = (pw_hi << 8) & 0xf00 | pw & 0x0ff;
89 }
90
writeCONTROL_REG(reg8 control)91 void WaveformGenerator::writeCONTROL_REG(reg8 control)
92 {
93 waveform = (control >> 4) & 0x0f;
94 ring_mod = control & 0x04;
95 sync = control & 0x02;
96
97 reg8 test_next = control & 0x08;
98
99 // Test bit set.
100 // The accumulator and the shift register are both cleared.
101 // NB! The shift register is not really cleared immediately. It seems like
102 // the individual bits in the shift register start to fade down towards
103 // zero when test is set. All bits reach zero within approximately
104 // $2000 - $4000 cycles.
105 // This is not modeled. There should fortunately be little audible output
106 // from this peculiar behavior.
107 if (test_next) {
108 accumulator = 0;
109 shift_register = 0;
110 }
111 // Test bit cleared.
112 // The accumulator starts counting, and the shift register is reset to
113 // the value 0x7ffff8.
114 // NB! The shift register will not actually be set to this exact value if the
115 // shift register bits have not had time to fade to zero.
116 // This is not modeled.
117 else if (test) {
118 shift_register = 0x7ffff8;
119 }
120
121 test = test_next;
122
123 // The gate bit is handled by the EnvelopeGenerator.
124 }
125
readOSC()126 reg8 WaveformGenerator::readOSC()
127 {
128 return output() >> 4;
129 }
130
131 // ----------------------------------------------------------------------------
132 // SID reset.
133 // ----------------------------------------------------------------------------
reset()134 void WaveformGenerator::reset()
135 {
136 accumulator = 0;
137 shift_register = 0x7ffff8;
138 freq = 0;
139 pw = 0;
140
141 test = 0;
142 ring_mod = 0;
143 sync = 0;
144
145 msb_rising = false;
146 }
147
148 RESID_NAMESPACE_STOP
149