1 // ---------------------------------------------------------------------------
2 // This file is part of reSID, a MOS6581 SID emulator engine.
3 // Copyright (C) 2004 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 // ----------------------------------------------------------------------------
24 // Constructor.
25 // ----------------------------------------------------------------------------
WaveformGenerator()26 WaveformGenerator::WaveformGenerator()
27 {
28 sync_source = this;
29
30 set_chip_model(MOS6581);
31
32 reset();
33 }
34
35
36 // ----------------------------------------------------------------------------
37 // Set sync source.
38 // ----------------------------------------------------------------------------
set_sync_source(WaveformGenerator * source)39 void WaveformGenerator::set_sync_source(WaveformGenerator* source)
40 {
41 sync_source = source;
42 source->sync_dest = this;
43 }
44
45
46 // ----------------------------------------------------------------------------
47 // Set chip model.
48 // ----------------------------------------------------------------------------
set_chip_model(chip_model model)49 void WaveformGenerator::set_chip_model(chip_model model)
50 {
51 if (model == MOS6581) {
52 wave__ST = wave6581__ST;
53 wave_P_T = wave6581_P_T;
54 wave_PS_ = wave6581_PS_;
55 wave_PST = wave6581_PST;
56 }
57 else {
58 wave__ST = wave8580__ST;
59 wave_P_T = wave8580_P_T;
60 wave_PS_ = wave8580_PS_;
61 wave_PST = wave8580_PST;
62 }
63 }
64
65
66 // ----------------------------------------------------------------------------
67 // Register functions.
68 // ----------------------------------------------------------------------------
writeFREQ_LO(reg8 freq_lo)69 void WaveformGenerator::writeFREQ_LO(reg8 freq_lo)
70 {
71 freq = ( freq & 0xff00 ) | ( freq_lo & 0x00ff );
72 }
73
writeFREQ_HI(reg8 freq_hi)74 void WaveformGenerator::writeFREQ_HI(reg8 freq_hi)
75 {
76 freq = ( (freq_hi << 8) & 0xff00 ) | ( freq & 0x00ff );
77 }
78
writePW_LO(reg8 pw_lo)79 void WaveformGenerator::writePW_LO(reg8 pw_lo)
80 {
81 pw = ( pw & 0xf00 ) | ( pw_lo & 0x0ff );
82 }
83
writePW_HI(reg8 pw_hi)84 void WaveformGenerator::writePW_HI(reg8 pw_hi)
85 {
86 pw = ( (pw_hi << 8) & 0xf00 ) | ( pw & 0x0ff );
87 }
88
writeCONTROL_REG(reg8 control)89 void WaveformGenerator::writeCONTROL_REG(reg8 control)
90 {
91 waveform = (control >> 4) & 0x0f;
92 ring_mod = control & 0x04;
93 sync = control & 0x02;
94
95 reg8 test_next = control & 0x08;
96
97 // Test bit set.
98 // The accumulator and the shift register are both cleared.
99 // NB! The shift register is not really cleared immediately. It seems like
100 // the individual bits in the shift register start to fade down towards
101 // zero when test is set. All bits reach zero within approximately
102 // $2000 - $4000 cycles.
103 // This is not modeled. There should fortunately be little audible output
104 // from this peculiar behavior.
105 if (test_next) {
106 accumulator = 0;
107 shift_register = 0;
108 }
109 // Test bit cleared.
110 // The accumulator starts counting, and the shift register is reset to
111 // the value 0x7ffff8.
112 // NB! The shift register will not actually be set to this exact value if the
113 // shift register bits have not had time to fade to zero.
114 // This is not modeled.
115 else if (test) {
116 shift_register = 0x7ffff8;
117 }
118
119 test = test_next;
120
121 // The gate bit is handled by the EnvelopeGenerator.
122 }
123
readOSC()124 reg8 WaveformGenerator::readOSC()
125 {
126 return output() >> 4;
127 }
128
129 // ----------------------------------------------------------------------------
130 // SID reset.
131 // ----------------------------------------------------------------------------
reset()132 void WaveformGenerator::reset()
133 {
134 accumulator = 0;
135 shift_register = 0x7ffff8;
136 freq = 0;
137 pw = 0;
138
139 test = 0;
140 ring_mod = 0;
141 sync = 0;
142
143 msb_rising = false;
144 }
145