152 lines
4.6 KiB
C++
152 lines
4.6 KiB
C++
// ---------------------------------------------------------------------------
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// This file is part of reSID, a MOS6581 SID emulator engine.
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// Copyright (C) 2004 Dag Lem <resid@nimrod.no>
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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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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// ---------------------------------------------------------------------------
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#define __WAVE_CC__
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#include "wave.h"
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// ----------------------------------------------------------------------------
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// Constructor.
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// ----------------------------------------------------------------------------
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WaveformGeneratorFP::WaveformGeneratorFP()
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{
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sync_source = this;
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set_chip_model(MOS6581FP);
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reset();
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}
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// ----------------------------------------------------------------------------
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// Set sync source.
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// ----------------------------------------------------------------------------
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void WaveformGeneratorFP::set_sync_source(WaveformGeneratorFP* source)
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{
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sync_source = source;
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source->sync_dest = this;
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}
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// ----------------------------------------------------------------------------
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// Set chip model.
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// ----------------------------------------------------------------------------
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void WaveformGeneratorFP::set_chip_model(chip_model model)
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{
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if (model == MOS6581FP) {
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wave__ST = wave6581__ST;
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wave_P_T = wave6581_P_T;
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wave_PS_ = wave6581_PS_;
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wave_PST = wave6581_PST;
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}
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else {
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wave__ST = wave8580__ST;
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wave_P_T = wave8580_P_T;
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wave_PS_ = wave8580_PS_;
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wave_PST = wave8580_PST;
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}
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}
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// ----------------------------------------------------------------------------
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// Register functions.
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// ----------------------------------------------------------------------------
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void WaveformGeneratorFP::writeFREQ_LO(reg8 freq_lo)
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{
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freq = (freq & 0xff00) | (freq_lo & 0x00ff);
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}
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void WaveformGeneratorFP::writeFREQ_HI(reg8 freq_hi)
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{
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freq = ((freq_hi << 8) & 0xff00) | (freq & 0x00ff);
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}
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/* The original form was (acc >> 12) >= pw, where truth value is not affected
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* by the contents of the low 12 bits. Therefore the lowest bits must be zero
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* in the new formulation acc >= (pw << 12). */
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void WaveformGeneratorFP::writePW_LO(reg8 pw_lo)
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{
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pw = (pw & 0xf00) | (pw_lo & 0x0ff);
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pw_acc_scale = pw << 12;
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}
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void WaveformGeneratorFP::writePW_HI(reg8 pw_hi)
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{
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pw = ((pw_hi << 8) & 0xf00) | (pw & 0x0ff);
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pw_acc_scale = pw << 12;
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}
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void WaveformGeneratorFP::writeCONTROL_REG(reg8 control)
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{
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waveform = (control >> 4) & 0x0f;
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ring_mod = control & 0x04;
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sync = control & 0x02;
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reg8 test_next = control & 0x08;
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/* SounDemoN found out that test bit can be used to control the noise
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* register. Hear the result in Bojojoing.sid. */
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// testbit set. invert bit 19 and write it to bit 1
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if (test_next && !test) {
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accumulator = 0;
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reg24 bit19 = (shift_register >> 19) & 1;
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shift_register = (shift_register & 0x7ffffd) | ((bit19^1) << 1);
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noise_overwrite_delay = 200000; /* 200 ms, probably too generous? */
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}
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// Test bit cleared.
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// The accumulator starts counting, and the shift register is reset to
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// the value 0x7ffff8.
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else if (!test_next && test) {
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reg24 bit0 = ((shift_register >> 22) ^ (shift_register >> 17)) & 0x1;
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shift_register <<= 1;
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shift_register |= bit0;
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}
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// clear output bits of shift register if noise and other waveforms
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// are selected simultaneously
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if (waveform > 8) {
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shift_register &= 0x7fffff^(1<<22)^(1<<20)^(1<<16)^(1<<13)^(1<<11)^(1<<7)^(1<<4)^(1<<2);
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}
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test = test_next;
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/* update noise anyway, just in case the above paths triggered */
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noise_output_cached = outputN___();
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}
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reg8 WaveformGeneratorFP::readOSC()
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{
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return output() >> 4;
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}
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// ----------------------------------------------------------------------------
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// SID reset.
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// ----------------------------------------------------------------------------
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void WaveformGeneratorFP::reset()
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{
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accumulator = 0;
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previous = 0;
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shift_register = 0x7ffffc;
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freq = 0;
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pw = 0;
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pw_acc_scale = 0;
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test = 0;
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writeCONTROL_REG(0);
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msb_rising = false;
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}
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