Integrator8580.h
/*
* This file is part of libsidplayfp, a SID player engine.
*
* Copyright 2011-2020 Leandro Nini <drfiemost@users.sourceforge.net>
* Copyright 2007-2010 Antti Lankila
* Copyright 2004, 2010 Dag Lem <resid@nimrod.no>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef INTEGRATOR8580_H
#define INTEGRATOR8580_H
#include <stdint.h>
#include <cassert>
#include "siddefs-fp.h"
namespace reSIDfp
{
class Integrator8580
{
private:
const unsigned short* opamp_rev;
mutable int vx;
mutable int vc;
unsigned short nVgt;
unsigned short n_dac;
const double Vth;
const double nKp;
const double vmin;
const double N16;
public:
Integrator8580(const unsigned short* opamp_rev, double Vth, double nKp, double vmin, double N16) :
opamp_rev(opamp_rev),
vx(0),
vc(0),
Vth(Vth),
nKp(nKp),
vmin(vmin),
N16(N16)
{
setV(1.5);
}
void setFc(double wl)
{
// Normalized current factor, 1 cycle at 1MHz.
// Fit in 5 bits.
const double tmp = (1 << 13) * nKp * wl;
assert(tmp > -0.5 && tmp < 65535.5);
n_dac = static_cast<unsigned short>(tmp + 0.5);
}
void setV(double v)
{
// Gate voltage is controlled by the switched capacitor voltage divider
// Ua = Ue * v = 4.76v 1<v<2
const double Vg = 4.76 * v;
const double Vgt = Vg - Vth;
// Vg - Vth, normalized so that translated values can be subtracted:
// Vgt - x = (Vgt - t) - (x - t)
const double tmp = N16 * (Vgt - vmin);
assert(tmp > -0.5 && tmp < 65535.5);
nVgt = static_cast<unsigned short>(tmp + 0.5);
}
int solve(int vi) const;
};
} // namespace reSIDfp
#if RESID_INLINING || defined(INTEGRATOR8580_CPP)
namespace reSIDfp
{
RESID_INLINE
int Integrator8580::solve(int vi) const
{
// Make sure we're not in subthreshold mode
assert(vx < nVgt);
// DAC voltages
const unsigned int Vgst = nVgt - vx;
const unsigned int Vgdt = (vi < nVgt) ? nVgt - vi : 0; // triode/saturation mode
const unsigned int Vgst_2 = Vgst * Vgst;
const unsigned int Vgdt_2 = Vgdt * Vgdt;
// DAC current, scaled by (1/m)*2^13*m*2^16*m*2^16*2^-15 = m*2^30
const int n_I_dac = n_dac * (static_cast<int>(Vgst_2 - Vgdt_2) >> 15);
// Change in capacitor charge.
vc += n_I_dac;
// vx = g(vc)
const int tmp = (vc >> 15) + (1 << 15);
assert(tmp < (1 << 16));
vx = opamp_rev[tmp];
// Return vo.
return vx - (vc >> 14);
}
} // namespace reSIDfp
#endif
#endif
reSIDfp::Integrator8580
Definition: Integrator8580.h:53
reSIDfp::Integrator8580::setV
void setV(double v)
Definition: Integrator8580.h:93