Integrator6581.h

/*
 * This file is part of libsidplayfp, a SID player engine.
 *
 * Copyright 2011-2023 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 INTEGRATOR6581_H
#define INTEGRATOR6581_H

#include "Integrator.h"
#include "FilterModelConfig6581.h"

#include <cstdint>
#include <cassert>

// uncomment to enable use of the slope factor
// in the EKV model
// actually produces worse results, needs investigation
//#define SLOPE_FACTOR

#include "siddefs-fp.h"

namespace reSIDfp
{

class Integrator6581 : public Integrator
{
    friend class State;

private:
    const double wlSnake;

#ifdef SLOPE_FACTOR
    // Slope factor n = 1/k
    // where k is the gate coupling coefficient
    // k = Cox/(Cox+Cdep) ~ 0.7 (depends on gate voltage)
    mutable double n;
#endif

    uint32_t nVddt_Vw_2;

    const uint16_t nVddt;
    const uint16_t nVt;
    const uint16_t nVmin;

    FilterModelConfig6581& fmc;

public:
    explicit Integrator6581(FilterModelConfig6581& new_fmc) :
        wlSnake(new_fmc.getWL_snake()),
#ifdef SLOPE_FACTOR
        n(1.4),
#endif
        nVddt_Vw_2(0),
        nVddt(new_fmc.getNormalizedValue(new_fmc.getVddt())),
        nVt(new_fmc.getNormalizedValue(new_fmc.getVth())),
        nVmin(new_fmc.getNVmin()),
        fmc(new_fmc) {}

    void setVw(uint16_t Vw) { nVddt_Vw_2 = ((nVddt - Vw) * (nVddt - Vw)) >> 1; }

    int32_t solve(int32_t vi) const override;
};

} // namespace reSIDfp

#endif