110 lines
3.4 KiB
Text
110 lines
3.4 KiB
Text
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// ---------------------------------------------------------------------------
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// This file is part of reSID, a MOS6581 SID emulator engine.
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// Copyright (C) 2010 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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#ifndef RESID_VOICE_H
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#define RESID_VOICE_H
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#include "resid-config.h"
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#include "wave.h"
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#include "envelope.h"
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namespace reSID
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{
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class Voice
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{
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public:
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Voice();
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void set_chip_model(chip_model model);
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void set_sync_source(Voice*);
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void reset();
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void writeCONTROL_REG(reg8);
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// Amplitude modulated waveform output.
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// Range [-2048*255, 2047*255].
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int output();
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WaveformGenerator wave;
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EnvelopeGenerator envelope;
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protected:
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// Waveform D/A zero level.
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short wave_zero;
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friend class SID;
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};
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// ----------------------------------------------------------------------------
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// Inline functions.
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// The following function is defined inline because it is called every
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// time a sample is calculated.
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// ----------------------------------------------------------------------------
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#if RESID_INLINING || defined(RESID_VOICE_CC)
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// ----------------------------------------------------------------------------
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// Amplitude modulated waveform output (20 bits).
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// Ideal range [-2048*255, 2047*255].
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// ----------------------------------------------------------------------------
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// The output for a voice is produced by a multiplying DAC, where the
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// waveform output modulates the envelope output.
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//
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// As noted by Bob Yannes: "The 8-bit output of the Envelope Generator was then
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// sent to the Multiplying D/A converter to modulate the amplitude of the
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// selected Oscillator Waveform (to be technically accurate, actually the
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// waveform was modulating the output of the Envelope Generator, but the result
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// is the same)".
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//
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// 7 6 5 4 3 2 1 0 VGND
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// | | | | | | | | | Missing
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// 2R 2R 2R 2R 2R 2R 2R 2R 2R termination
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// | | | | | | | | |
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// --R---R---R---R---R---R---R-- ---
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// | _____
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// __|__ __|__ |
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// ----- ===== |
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// | | | | |
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// 12V --- ----- ------- GND
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// |
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// vout
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//
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// Bit on: wout (see figure in wave.h)
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// Bit off: 5V (VGND)
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//
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// As is the case with all MOS 6581 DACs, the termination to (virtual) ground
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// at bit 0 is missing. The MOS 8580 has correct termination.
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//
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RESID_INLINE
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int Voice::output()
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{
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// Multiply oscillator output with envelope output.
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return (wave.output() - wave_zero)*envelope.output();
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}
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#endif // RESID_INLINING || defined(RESID_VOICE_CC)
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} // namespace reSID
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#endif // not RESID_VOICE_H
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