//  ---------------------------------------------------------------------------
//  This file is part of reSID, a MOS6581 SID emulator engine.
//  Copyright (C) 2004  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//  ---------------------------------------------------------------------------

#include "ep128emu.hpp"
#include "voice.hpp"

namespace Ep128 {

  // --------------------------------------------------------------------------
  // Constructor.
  // --------------------------------------------------------------------------
  Voice::Voice()
  {
    set_chip_model(MOS6581);
  }

  // --------------------------------------------------------------------------
  // Set chip model.
  // --------------------------------------------------------------------------
  void Voice::set_chip_model(chip_model model)
  {
    wave.set_chip_model(model);
    envelope.set_chip_model(model);

    if (model == MOS6581) {
      // The waveform D/A converter introduces a DC offset in the signal
      // to the envelope multiplying D/A converter. The "zero" level of
      // the waveform D/A converter can be found as follows:
      //
      // Measure the "zero" voltage of voice 3 on the SID audio output
      // pin, routing only voice 3 to the mixer ($d417 = $0b, $d418 =
      // $0f, all other registers zeroed).
      //
      // Then set the sustain level for voice 3 to maximum and search for
      // the waveform output value yielding the same voltage as found
      // above. This is done by trying out different waveform output
      // values until the correct value is found, e.g. with the following
      // program:
      //
      //        lda #$08
      //        sta $d412
      //        lda #$0b
      //        sta $d417
      //        lda #$0f
      //        sta $d418
      //        lda #$f0
      //        sta $d414
      //        lda #$21
      //        sta $d412
      //        lda #$01
      //        sta $d40e
      //
      //        ldx #$00
      //        lda #$38    ; Tweak this to find the "zero" level
      //l       cmp $d41b
      //        bne l
      //        stx $d40e   ; Stop frequency counter - freeze waveform output
      //        brk
      //
      // The waveform output range is 0x000 to 0xfff, so the "zero"
      // level should ideally have been 0x800. In the measured chip, the
      // waveform output "zero" level was found to be 0x380 (i.e. $d41b
      // = 0x38) at an audio output voltage of 5.94V.
      //
      // With knowledge of the mixer op-amp characteristics, further estimates
      // of waveform voltages can be obtained by sampling the EXT IN pin.
      // From EXT IN samples, the corresponding waveform output can be found by
      // using the model for the mixer.
      //
      // Such measurements have been done on a chip marked MOS 6581R4AR
      // 0687 14, and the following results have been obtained:
      // * The full range of one voice is approximately 1.5V.
      // * The "zero" level rides at approximately 5.0V.
      //
      wave_zero = 0x380;
    }
    else {
      // No DC offsets in the MOS8580.
      wave_zero = 0x800;
    }
  }

  // --------------------------------------------------------------------------
  // Set sync source.
  // --------------------------------------------------------------------------
  void Voice::set_sync_source(Voice* source)
  {
    wave.set_sync_source(&source->wave);
  }

  // --------------------------------------------------------------------------
  // Register functions.
  // --------------------------------------------------------------------------
  void Voice::writeCONTROL_REG(reg8 control)
  {
    wave.writeCONTROL_REG(control);
    envelope.writeCONTROL_REG(control);
  }

  // --------------------------------------------------------------------------
  // SID reset.
  // --------------------------------------------------------------------------
  void Voice::reset()
  {
    wave.reset();
    envelope.reset();
  }

}       // namespace Ep128

