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 // ----------------------------------------------------------------------------
WaveformGeneratorFP()26 WaveformGeneratorFP::WaveformGeneratorFP()
27 {
28 sync_source = this;
29
30 set_chip_model(MOS6581FP);
31
32 reset();
33 }
34
35
36 // ----------------------------------------------------------------------------
37 // Set sync source.
38 // ----------------------------------------------------------------------------
set_sync_source(WaveformGeneratorFP * source)39 void WaveformGeneratorFP::set_sync_source(WaveformGeneratorFP* 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 WaveformGeneratorFP::set_chip_model(chip_model model)
50 {
51 if (model == MOS6581FP) {
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 WaveformGeneratorFP::writeFREQ_LO(reg8 freq_lo)
70 {
71 freq = (freq & 0xff00) | (freq_lo & 0x00ff);
72 }
73
writeFREQ_HI(reg8 freq_hi)74 void WaveformGeneratorFP::writeFREQ_HI(reg8 freq_hi)
75 {
76 freq = ((freq_hi << 8) & 0xff00) | (freq & 0x00ff);
77 }
78
79 /* The original form was (acc >> 12) >= pw, where truth value is not affected
80 * by the contents of the low 12 bits. Therefore the lowest bits must be zero
81 * in the new formulation acc >= (pw << 12). */
writePW_LO(reg8 pw_lo)82 void WaveformGeneratorFP::writePW_LO(reg8 pw_lo)
83 {
84 pw = (pw & 0xf00) | (pw_lo & 0x0ff);
85 pw_acc_scale = pw << 12;
86 }
87
writePW_HI(reg8 pw_hi)88 void WaveformGeneratorFP::writePW_HI(reg8 pw_hi)
89 {
90 pw = ((pw_hi << 8) & 0xf00) | (pw & 0x0ff);
91 pw_acc_scale = pw << 12;
92 }
93
writeCONTROL_REG(reg8 control)94 void WaveformGeneratorFP::writeCONTROL_REG(reg8 control)
95 {
96 waveform = (control >> 4) & 0x0f;
97 ring_mod = control & 0x04;
98 sync = control & 0x02;
99
100 reg8 test_next = control & 0x08;
101
102 /* SounDemoN found out that test bit can be used to control the noise
103 * register. Hear the result in Bojojoing.sid. */
104
105 // testbit set. invert bit 19 and write it to bit 1
106 if (test_next && !test) {
107 accumulator = 0;
108 reg24 bit19 = (shift_register >> 19) & 1;
109 shift_register = (shift_register & 0x7ffffd) | ((bit19^1) << 1);
110 noise_overwrite_delay = 200000; /* 200 ms, probably too generous? */
111 }
112 // Test bit cleared.
113 // The accumulator starts counting, and the shift register is reset to
114 // the value 0x7ffff8.
115 else if (!test_next && test) {
116 reg24 bit0 = ((shift_register >> 22) ^ (shift_register >> 17)) & 0x1;
117 shift_register <<= 1;
118 shift_register |= bit0;
119 }
120 // clear output bits of shift register if noise and other waveforms
121 // are selected simultaneously
122 if (waveform > 8) {
123 shift_register &= 0x7fffff^(1<<22)^(1<<20)^(1<<16)^(1<<13)^(1<<11)^(1<<7)^(1<<4)^(1<<2);
124 }
125
126 test = test_next;
127
128 /* update noise anyway, just in case the above paths triggered */
129 noise_output_cached = outputN___();
130 }
131
readOSC()132 reg8 WaveformGeneratorFP::readOSC()
133 {
134 return output() >> 4;
135 }
136
137 // ----------------------------------------------------------------------------
138 // SID reset.
139 // ----------------------------------------------------------------------------
reset()140 void WaveformGeneratorFP::reset()
141 {
142 accumulator = 0;
143 previous = 0;
144 shift_register = 0x7ffffc;
145 freq = 0;
146 pw = 0;
147 pw_acc_scale = 0;
148 test = 0;
149 writeCONTROL_REG(0);
150 msb_rising = false;
151 }
152