libsidplayfp 2.6.0
Integrator8580.h
1/*
2 * This file is part of libsidplayfp, a SID player engine.
3 *
4 * Copyright 2011-2023 Leandro Nini <drfiemost@users.sourceforge.net>
5 * Copyright 2007-2010 Antti Lankila
6 * Copyright 2004, 2010 Dag Lem <resid@nimrod.no>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
21 */
22
23#ifndef INTEGRATOR8580_H
24#define INTEGRATOR8580_H
25
26#include "FilterModelConfig8580.h"
27
28#include <stdint.h>
29#include <cassert>
30
31#include "siddefs-fp.h"
32
33namespace reSIDfp
34{
35
55{
56private:
57 mutable int vx;
58 mutable int vc;
59
60 unsigned short nVgt;
61 unsigned short n_dac;
62
63 const FilterModelConfig8580* fmc;
64
65public:
67 vx(0),
68 vc(0),
69 fmc(fmc)
70 {
71 setV(1.5);
72 }
73
77 void setFc(double wl)
78 {
79 // Normalized current factor, 1 cycle at 1MHz.
80 // Fit in 5 bits.
81 n_dac = fmc->getNormalizedCurrentFactor(wl);
82 }
83
87 void setV(double v)
88 {
89 // Gate voltage is controlled by the switched capacitor voltage divider
90 // Ua = Ue * v = 4.76v 1<v<2
91 assert(v > 1.0 && v < 2.0);
92 const double Vg = 4.76 * v;
93 const double Vgt = Vg - fmc->getVth();
94
95 // Vg - Vth, normalized so that translated values can be subtracted:
96 // Vgt - x = (Vgt - t) - (x - t)
97 nVgt = fmc->getNormalizedValue(Vgt);
98 }
99
100 int solve(int vi) const;
101};
102
103} // namespace reSIDfp
104
105#if RESID_INLINING || defined(INTEGRATOR8580_CPP)
106
107namespace reSIDfp
108{
109
110RESID_INLINE
111int Integrator8580::solve(int vi) const
112{
113 // Make sure we're not in subthreshold mode
114 assert(vx < nVgt);
115
116 // DAC voltages
117 const unsigned int Vgst = nVgt - vx;
118 const unsigned int Vgdt = (vi < nVgt) ? nVgt - vi : 0; // triode/saturation mode
119
120 const unsigned int Vgst_2 = Vgst * Vgst;
121 const unsigned int Vgdt_2 = Vgdt * Vgdt;
122
123 // DAC current, scaled by (1/m)*2^13*m*2^16*m*2^16*2^-15 = m*2^30
124 const int n_I_dac = n_dac * (static_cast<int>(Vgst_2 - Vgdt_2) >> 15);
125
126 // Change in capacitor charge.
127 vc += n_I_dac;
128
129 // vx = g(vc)
130 const int tmp = (vc >> 15) + (1 << 15);
131 assert(tmp < (1 << 16));
132 vx = fmc->getOpampRev(tmp);
133
134 // Return vo.
135 return vx - (vc >> 14);
136}
137
138} // namespace reSIDfp
139
140#endif
141
142#endif
Definition FilterModelConfig8580.h:41
Definition Integrator8580.h:55
void setFc(double wl)
Definition Integrator8580.h:77
void setV(double v)
Definition Integrator8580.h:87