libsidplayfp  2.2.2
Integrator8580.h
1 /*
2  * This file is part of libsidplayfp, a SID player engine.
3  *
4  * Copyright 2011-2020 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 <stdint.h>
27 #include <cassert>
28 
29 #include "siddefs-fp.h"
30 
31 namespace reSIDfp
32 {
33 
53 {
54 private:
55  const unsigned short* opamp_rev;
56 
57  mutable int vx;
58  mutable int vc;
59 
60  unsigned short nVgt;
61  unsigned short n_dac;
62 
63  const double Vth;
64  const double nKp;
65  const double vmin;
66  const double N16;
67 
68 public:
69  Integrator8580(const unsigned short* opamp_rev, double Vth, double nKp, double vmin, double N16) :
70  opamp_rev(opamp_rev),
71  vx(0),
72  vc(0),
73  Vth(Vth),
74  nKp(nKp),
75  vmin(vmin),
76  N16(N16)
77  {
78  setV(1.5);
79  }
80 
81  void setFc(double wl)
82  {
83  // Normalized current factor, 1 cycle at 1MHz.
84  // Fit in 5 bits.
85  const double tmp = (1 << 13) * nKp * wl;
86  assert(tmp > -0.5 && tmp < 65535.5);
87  n_dac = static_cast<unsigned short>(tmp + 0.5);
88  }
89 
93  void setV(double v)
94  {
95  // Gate voltage is controlled by the switched capacitor voltage divider
96  // Ua = Ue * v = 4.76v 1<v<2
97  const double Vg = 4.76 * v;
98  const double Vgt = Vg - Vth;
99 
100  // Vg - Vth, normalized so that translated values can be subtracted:
101  // Vgt - x = (Vgt - t) - (x - t)
102  const double tmp = N16 * (Vgt - vmin);
103  assert(tmp > -0.5 && tmp < 65535.5);
104  nVgt = static_cast<unsigned short>(tmp + 0.5);
105  }
106 
107  int solve(int vi) const;
108 };
109 
110 } // namespace reSIDfp
111 
112 #if RESID_INLINING || defined(INTEGRATOR8580_CPP)
113 
114 namespace reSIDfp
115 {
116 
117 RESID_INLINE
118 int Integrator8580::solve(int vi) const
119 {
120  // Make sure we're not in subthreshold mode
121  assert(vx < nVgt);
122 
123  // DAC voltages
124  const unsigned int Vgst = nVgt - vx;
125  const unsigned int Vgdt = (vi < nVgt) ? nVgt - vi : 0; // triode/saturation mode
126 
127  const unsigned int Vgst_2 = Vgst * Vgst;
128  const unsigned int Vgdt_2 = Vgdt * Vgdt;
129 
130  // DAC current, scaled by (1/m)*2^13*m*2^16*m*2^16*2^-15 = m*2^30
131  const int n_I_dac = n_dac * (static_cast<int>(Vgst_2 - Vgdt_2) >> 15);
132 
133  // Change in capacitor charge.
134  vc += n_I_dac;
135 
136  // vx = g(vc)
137  const int tmp = (vc >> 15) + (1 << 15);
138  assert(tmp < (1 << 16));
139  vx = opamp_rev[tmp];
140 
141  // Return vo.
142  return vx - (vc >> 14);
143 }
144 
145 } // namespace reSIDfp
146 
147 #endif
148 
149 #endif
Definition: Integrator8580.h:53
void setV(double v)
Definition: Integrator8580.h:93