342 lines
7.4 KiB
C++
342 lines
7.4 KiB
C++
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// Nes_Snd_Emu 0.1.7. http://www.slack.net/~ant/libs/
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#include "Nes_Apu.h"
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/* Copyright (C) 2003-2005 Shay Green. This module is free software; you
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can redistribute it and/or modify it under the terms of the GNU Lesser
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General Public License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version. This
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module is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
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more details. You should have received a copy of the GNU Lesser General
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Public License along with this module; 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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#include BLARGG_SOURCE_BEGIN
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Nes_Apu::Nes_Apu()
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{
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dmc.apu = this;
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dmc.rom_reader = NULL;
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square1.synth = &square_synth;
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square2.synth = &square_synth;
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irq_notifier_ = NULL;
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oscs [0] = &square1;
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oscs [1] = &square2;
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oscs [2] = ▵
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oscs [3] = &noise;
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oscs [4] = &dmc;
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output( NULL );
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volume( 1.0 );
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reset( false );
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}
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Nes_Apu::~Nes_Apu()
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{
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}
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void Nes_Apu::treble_eq( const blip_eq_t& eq )
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{
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square_synth.treble_eq( eq );
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triangle.synth.treble_eq( eq );
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noise.synth.treble_eq( eq );
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dmc.synth.treble_eq( eq );
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}
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void Nes_Apu::buffer_cleared()
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{
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square1.last_amp = 0;
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square2.last_amp = 0;
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triangle.last_amp = 0;
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noise.last_amp = 0;
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dmc.last_amp = 0;
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}
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void Nes_Apu::enable_nonlinear( double v )
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{
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dmc.nonlinear = true;
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square_synth.volume( 1.3 * 0.25751258 / 0.742467605 * 0.25 * v );
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const double tnd = 0.75 / 202 * 0.48;
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triangle.synth.volume_unit( 3 * tnd );
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noise.synth.volume_unit( 2 * tnd );
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dmc.synth.volume_unit( tnd );
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buffer_cleared();
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}
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void Nes_Apu::volume( double v )
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{
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dmc.nonlinear = false;
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square_synth.volume( 0.1128 * v );
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triangle.synth.volume( 0.12765 * v );
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noise.synth.volume( 0.0741 * v );
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dmc.synth.volume( 0.42545 * v );
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}
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void Nes_Apu::output( Blip_Buffer* buffer )
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{
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for ( int i = 0; i < osc_count; i++ )
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osc_output( i, buffer );
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}
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void Nes_Apu::reset( bool pal_mode, int initial_dmc_dac )
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{
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// to do: time pal frame periods exactly
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frame_period = pal_mode ? 8314 : 7458;
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dmc.pal_mode = pal_mode;
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square1.reset();
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square2.reset();
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triangle.reset();
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noise.reset();
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dmc.reset();
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last_time = 0;
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osc_enables = 0;
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irq_flag = false;
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earliest_irq_ = no_irq;
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frame_delay = 1;
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write_register( 0, 0x4017, 0x00 );
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write_register( 0, 0x4015, 0x00 );
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for ( cpu_addr_t addr = start_addr; addr <= 0x4013; addr++ )
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write_register( 0, addr, (addr & 3) ? 0x00 : 0x10 );
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dmc.dac = initial_dmc_dac;
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if ( !dmc.nonlinear )
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dmc.last_amp = initial_dmc_dac; // prevent output transition
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}
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void Nes_Apu::irq_changed()
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{
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cpu_time_t new_irq = dmc.next_irq;
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if ( dmc.irq_flag | irq_flag ) {
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new_irq = 0;
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}
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else if ( new_irq > next_irq ) {
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new_irq = next_irq;
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}
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if ( new_irq != earliest_irq_ ) {
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earliest_irq_ = new_irq;
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if ( irq_notifier_ )
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irq_notifier_( irq_data );
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}
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}
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// frames
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void Nes_Apu::run_until( cpu_time_t end_time )
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{
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require( end_time >= last_time );
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if ( end_time == last_time )
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return;
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while ( true )
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{
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// earlier of next frame time or end time
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cpu_time_t time = last_time + frame_delay;
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if ( time > end_time )
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time = end_time;
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frame_delay -= time - last_time;
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// run oscs to present
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square1.run( last_time, time );
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square2.run( last_time, time );
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triangle.run( last_time, time );
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noise.run( last_time, time );
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dmc.run( last_time, time );
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last_time = time;
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if ( time == end_time )
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break; // no more frames to run
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// take frame-specific actions
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frame_delay = frame_period;
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switch ( frame++ )
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{
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case 0:
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if ( !(frame_mode & 0xc0) ) {
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next_irq = time + frame_period * 4 + 1;
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irq_flag = true;
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}
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// fall through
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case 2:
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// clock length and sweep on frames 0 and 2
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square1.clock_length( 0x20 );
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square2.clock_length( 0x20 );
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noise.clock_length( 0x20 );
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triangle.clock_length( 0x80 ); // different bit for halt flag on triangle
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square1.clock_sweep( -1 );
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square2.clock_sweep( 0 );
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break;
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case 1:
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// frame 1 is slightly shorter
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frame_delay -= 2;
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break;
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case 3:
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frame = 0;
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// frame 3 is almost twice as long in mode 1
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if ( frame_mode & 0x80 )
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frame_delay += frame_period - 6;
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break;
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}
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// clock envelopes and linear counter every frame
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triangle.clock_linear_counter();
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square1.clock_envelope();
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square2.clock_envelope();
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noise.clock_envelope();
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}
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}
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void Nes_Apu::end_frame( cpu_time_t end_time )
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{
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if ( end_time > last_time )
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run_until( end_time );
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// make times relative to new frame
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last_time -= end_time;
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require( last_time >= 0 );
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if ( next_irq != no_irq ) {
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next_irq -= end_time;
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assert( next_irq >= 0 );
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}
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if ( dmc.next_irq != no_irq ) {
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dmc.next_irq -= end_time;
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assert( dmc.next_irq >= 0 );
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}
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if ( earliest_irq_ != no_irq ) {
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earliest_irq_ -= end_time;
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if ( earliest_irq_ < 0 )
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earliest_irq_ = 0;
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}
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}
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// registers
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static const unsigned char length_table [0x20] = {
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0x0A, 0xFE, 0x14, 0x02, 0x28, 0x04, 0x50, 0x06,
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0xA0, 0x08, 0x3C, 0x0A, 0x0E, 0x0C, 0x1A, 0x0E,
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0x0C, 0x10, 0x18, 0x12, 0x30, 0x14, 0x60, 0x16,
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0xC0, 0x18, 0x48, 0x1A, 0x10, 0x1C, 0x20, 0x1E
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};
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void Nes_Apu::write_register( cpu_time_t time, cpu_addr_t addr, int data )
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{
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require( addr > 0x20 ); // addr must be actual address (i.e. 0x40xx)
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require( (unsigned) data <= 0xff );
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// Ignore addresses outside range
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if ( addr < start_addr || end_addr < addr )
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return;
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run_until( time );
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if ( addr < 0x4014 )
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{
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// Write to channel
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int osc_index = (addr - start_addr) >> 2;
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Nes_Osc* osc = oscs [osc_index];
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int reg = addr & 3;
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osc->regs [reg] = data;
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osc->reg_written [reg] = true;
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if ( osc_index == 4 )
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{
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// handle DMC specially
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dmc.write_register( reg, data );
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}
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else if ( reg == 3 )
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{
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// load length counter
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if ( (osc_enables >> osc_index) & 1 )
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osc->length_counter = length_table [(data >> 3) & 0x1f];
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// reset square phase
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if ( osc_index < 2 )
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((Nes_Square*) osc)->phase = Nes_Square::phase_range - 1;
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}
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}
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else if ( addr == 0x4015 )
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{
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// Channel enables
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for ( int i = osc_count; i--; )
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if ( !((data >> i) & 1) )
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oscs [i]->length_counter = 0;
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bool recalc_irq = dmc.irq_flag;
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dmc.irq_flag = false;
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int old_enables = osc_enables;
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osc_enables = data;
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if ( !(data & 0x10) ) {
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dmc.next_irq = no_irq;
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recalc_irq = true;
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}
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else if ( !(old_enables & 0x10) ) {
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dmc.start(); // dmc just enabled
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}
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if ( recalc_irq )
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irq_changed();
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}
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else if ( addr == 0x4017 )
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{
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// Frame mode
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frame_mode = data;
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bool irq_enabled = !(data & 0x40);
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irq_flag &= irq_enabled;
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next_irq = no_irq;
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// mode 1
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frame_delay = (frame_delay & 1);
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frame = 0;
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if ( !(data & 0x80) )
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{
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// mode 0
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frame = 1;
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frame_delay += frame_period;
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if ( irq_enabled )
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next_irq = time + frame_delay + frame_period * 3;
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}
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irq_changed();
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}
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}
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int Nes_Apu::read_status( cpu_time_t time )
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{
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run_until( time - 1 );
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int result = (dmc.irq_flag << 7) | (irq_flag << 6);
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for ( int i = 0; i < osc_count; i++ )
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if ( oscs [i]->length_counter )
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result |= 1 << i;
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run_until( time );
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if ( irq_flag ) {
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irq_flag = false;
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irq_changed();
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}
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return result;
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}
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