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149 lines
4.2 KiB
149 lines
4.2 KiB
// ---------------------------------------------------------------------------
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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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RESID_NAMESPACE_START
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// ----------------------------------------------------------------------------
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// Constructor.
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// ----------------------------------------------------------------------------
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WaveformGenerator::WaveformGenerator()
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{
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sync_source = this;
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set_chip_model(MOS6581);
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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 WaveformGenerator::set_sync_source(WaveformGenerator* 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 WaveformGenerator::set_chip_model(chip_model model)
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{
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if (model == MOS6581) {
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wave__ST = &wave6581__ST[0];
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wave_P_T = &wave6581_P_T[0];
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wave_PS_ = &wave6581_PS_[0];
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wave_PST = &wave6581_PST[0];
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}
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else {
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wave__ST = &wave8580__ST[0];
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wave_P_T = &wave8580_P_T[0];
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wave_PS_ = &wave8580_PS_[0];
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wave_PST = &wave8580_PST[0];
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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 WaveformGenerator::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 WaveformGenerator::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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void WaveformGenerator::writePW_LO(reg8 pw_lo)
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{
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pw = (pw & 0xf00) | (pw_lo & 0x0ff);
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}
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void WaveformGenerator::writePW_HI(reg8 pw_hi)
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{
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pw = ((pw_hi << 8) & 0xf00) | (pw & 0x0ff);
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}
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void WaveformGenerator::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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// Test bit set.
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// The accumulator and the shift register are both cleared.
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// NB! The shift register is not really cleared immediately. It seems like
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// the individual bits in the shift register start to fade down towards
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// zero when test is set. All bits reach zero within approximately
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// $2000 - $4000 cycles.
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// This is not modeled. There should fortunately be little audible output
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// from this peculiar behavior.
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if (test_next) {
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accumulator = 0;
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shift_register = 0;
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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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// NB! The shift register will not actually be set to this exact value if the
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// shift register bits have not had time to fade to zero.
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// This is not modeled.
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else if (test) {
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shift_register = 0x7ffff8;
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}
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test = test_next;
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// The gate bit is handled by the EnvelopeGenerator.
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}
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reg8 WaveformGenerator::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 WaveformGenerator::reset()
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{
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accumulator = 0;
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shift_register = 0x7ffff8;
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freq = 0;
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pw = 0;
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test = 0;
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ring_mod = 0;
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sync = 0;
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msb_rising = false;
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}
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RESID_NAMESPACE_STOP
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