98 lines
3.2 KiB
C++
98 lines
3.2 KiB
C++
/*
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* This file is part of libsidplayfp, a SID player engine.
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*
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* Copyright 2014 Leandro Nini <drfiemost@users.sourceforge.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include "Integrator6581.h"
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#ifdef SLOPE_FACTOR
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# include <cmath>
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# include "sidcxx11.h"
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#endif
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namespace reSIDfp
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{
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int Integrator6581::solve(int vi) const
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{
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// Make sure Vgst>0 so we're not in subthreshold mode
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assert(vx < nVddt);
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// Check that transistor is actually in triode mode
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// Vds < Vgs - Vth
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assert(vi < nVddt);
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// "Snake" voltages for triode mode calculation.
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const unsigned int Vgst = nVddt - vx;
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const unsigned int Vgdt = nVddt - vi;
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const unsigned int Vgst_2 = Vgst * Vgst;
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const unsigned int Vgdt_2 = Vgdt * Vgdt;
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// "Snake" current, scaled by (1/m)*2^13*m*2^16*m*2^16*2^-15 = m*2^30
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const int n_I_snake = fmc.getNormalizedCurrentFactor(wlSnake) * (static_cast<int>(Vgst_2 - Vgdt_2) >> 15);
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// VCR gate voltage. // Scaled by m*2^16
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// Vg = Vddt - sqrt(((Vddt - Vw)^2 + Vgdt^2)/2)
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const int nVg = static_cast<int>(fmc.getVcr_nVg((nVddt_Vw_2 + (Vgdt_2 >> 1)) >> 16));
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#ifdef SLOPE_FACTOR
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const double nVp = static_cast<double>(nVg - nVt) / n; // Pinch-off voltage
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const int kVgt = static_cast<int>(nVp + 0.5) - nVmin;
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#else
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const int kVgt = (nVg - nVt) - nVmin;
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#endif
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// VCR voltages for EKV model table lookup.
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const int kVgt_Vs = (kVgt - vx) + (1 << 15);
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assert((kVgt_Vs >= 0) && (kVgt_Vs < (1 << 16)));
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const int kVgt_Vd = (kVgt - vi) + (1 << 15);
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assert((kVgt_Vd >= 0) && (kVgt_Vd < (1 << 16)));
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// VCR current, scaled by m*2^15*2^15 = m*2^30
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const unsigned int If = static_cast<unsigned int>(fmc.getVcr_n_Ids_term(kVgt_Vs)) << 15;
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const unsigned int Ir = static_cast<unsigned int>(fmc.getVcr_n_Ids_term(kVgt_Vd)) << 15;
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#ifdef SLOPE_FACTOR
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const double iVcr = static_cast<double>(If - Ir);
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const int n_I_vcr = static_cast<int>(iVcr * n);
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#else
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const int n_I_vcr = If - Ir;
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#endif
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#ifdef SLOPE_FACTOR
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// estimate new slope factor based on gate voltage
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constexpr double gamma = 1.0; // body effect factor
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constexpr double phi = 0.8; // bulk Fermi potential
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const double Vp = nVp / fmc.getN16();
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n = 1. + (gamma / (2. * std::sqrt(Vp + phi + 4. * fmc.getUt())));
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assert((n > 1.2) && (n < 1.8));
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#endif
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// Change in capacitor charge.
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vc += n_I_snake + n_I_vcr;
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// vx = g(vc)
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const int tmp = (vc >> 15) + (1 << 15);
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assert(tmp < (1 << 16));
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vx = fmc.getOpampRev(tmp);
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// Return vo.
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return vx - (vc >> 14);
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}
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} // namespace reSIDfp
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