307 lines
7.3 KiB
C++
307 lines
7.3 KiB
C++
// Gb_Snd_Emu 0.1.5. http://www.slack.net/~ant/
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#include "Gb_Apu.h"
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#include <string.h>
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/* Copyright (C) 2003-2006 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 more
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details. You should have received a copy of the GNU Lesser General Public
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License along with this module; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
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#include "blargg_source.h"
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unsigned const vol_reg = 0xFF24;
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unsigned const status_reg = 0xFF26;
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Gb_Apu::Gb_Apu()
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{
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square1.synth = &square_synth;
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square2.synth = &square_synth;
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wave.synth = &other_synth;
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noise.synth = &other_synth;
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oscs [0] = &square1;
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oscs [1] = &square2;
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oscs [2] = &wave;
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oscs [3] = &noise;
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for ( int i = 0; i < osc_count; i++ )
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{
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Gb_Osc& osc = *oscs [i];
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osc.regs = ®s [i * 5];
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osc.output = 0;
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osc.outputs [0] = 0;
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osc.outputs [1] = 0;
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osc.outputs [2] = 0;
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osc.outputs [3] = 0;
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}
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set_tempo( 1.0 );
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volume( 1.0 );
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reset();
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}
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void Gb_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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other_synth.treble_eq( eq );
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}
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void Gb_Apu::osc_output( int index, Blip_Buffer* center, Blip_Buffer* left, Blip_Buffer* right )
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{
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require( (unsigned) index < osc_count );
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require( (center && left && right) || (!center && !left && !right) );
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Gb_Osc& osc = *oscs [index];
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osc.outputs [1] = right;
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osc.outputs [2] = left;
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osc.outputs [3] = center;
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osc.output = osc.outputs [osc.output_select];
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}
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void Gb_Apu::output( Blip_Buffer* center, Blip_Buffer* left, Blip_Buffer* right )
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{
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for ( int i = 0; i < osc_count; i++ )
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osc_output( i, center, left, right );
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}
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void Gb_Apu::update_volume()
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{
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// TODO: doesn't handle differing left/right global volume (support would
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// require modification to all oscillator code)
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int data = regs [vol_reg - start_addr];
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double vol = (max( data & 7, data >> 4 & 7 ) + 1) * volume_unit;
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square_synth.volume( vol );
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other_synth.volume( vol );
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}
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static unsigned char const powerup_regs [0x20] = {
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0x80,0x3F,0x00,0xFF,0xBF, // square 1
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0xFF,0x3F,0x00,0xFF,0xBF, // square 2
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0x7F,0xFF,0x9F,0xFF,0xBF, // wave
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0xFF,0xFF,0x00,0x00,0xBF, // noise
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0x00, // left/right enables
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0x77, // master volume
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0x80, // power
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0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF
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};
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void Gb_Apu::set_tempo( double t )
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{
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frame_period = 4194304 / 256; // 256 Hz
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if ( t != 1.0 )
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frame_period = blip_time_t (frame_period / t);
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}
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void Gb_Apu::reset()
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{
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next_frame_time = 0;
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last_time = 0;
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frame_count = 0;
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square1.reset();
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square2.reset();
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wave.reset();
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noise.reset();
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noise.bits = 1;
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wave.wave_pos = 0;
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// avoid click at beginning
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regs [vol_reg - start_addr] = 0x77;
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update_volume();
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regs [status_reg - start_addr] = 0x01; // force power
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write_register( 0, status_reg, 0x00 );
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static unsigned char const initial_wave [] = {
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0x84,0x40,0x43,0xAA,0x2D,0x78,0x92,0x3C, // wave table
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0x60,0x59,0x59,0xB0,0x34,0xB8,0x2E,0xDA
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};
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memcpy( wave.wave, initial_wave, sizeof wave.wave );
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}
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void Gb_Apu::run_until( blip_time_t end_time )
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{
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require( end_time >= last_time ); // end_time must not be before previous 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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blip_time_t time = next_frame_time;
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if ( time > end_time )
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time = end_time;
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// run oscillators
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for ( int i = 0; i < osc_count; ++i )
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{
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Gb_Osc& osc = *oscs [i];
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if ( osc.output )
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{
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osc.output->set_modified(); // TODO: misses optimization opportunities?
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int playing = false;
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if ( osc.enabled && osc.volume &&
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(!(osc.regs [4] & osc.len_enabled_mask) || osc.length) )
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playing = -1;
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switch ( i )
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{
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case 0: square1.run( last_time, time, playing ); break;
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case 1: square2.run( last_time, time, playing ); break;
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case 2: wave .run( last_time, time, playing ); break;
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case 3: noise .run( last_time, time, playing ); break;
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}
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}
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}
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last_time = time;
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if ( time == end_time )
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break;
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next_frame_time += frame_period;
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// 256 Hz actions
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square1.clock_length();
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square2.clock_length();
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wave.clock_length();
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noise.clock_length();
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frame_count = (frame_count + 1) & 3;
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if ( frame_count == 0 )
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{
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// 64 Hz actions
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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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if ( frame_count & 1 )
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square1.clock_sweep(); // 128 Hz action
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}
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}
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void Gb_Apu::end_frame( blip_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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assert( next_frame_time >= end_time );
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next_frame_time -= end_time;
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assert( last_time >= end_time );
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last_time -= end_time;
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}
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void Gb_Apu::write_register( blip_time_t time, unsigned addr, int data )
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{
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require( (unsigned) data < 0x100 );
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int reg = addr - start_addr;
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if ( (unsigned) reg >= register_count )
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return;
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run_until( time );
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int old_reg = regs [reg];
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regs [reg] = data;
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if ( addr < vol_reg )
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{
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write_osc( reg / 5, reg, data );
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}
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else if ( addr == vol_reg && data != old_reg ) // global volume
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{
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// return all oscs to 0
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for ( int i = 0; i < osc_count; i++ )
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{
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Gb_Osc& osc = *oscs [i];
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int amp = osc.last_amp;
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osc.last_amp = 0;
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if ( amp && osc.enabled && osc.output )
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other_synth.offset( time, -amp, osc.output );
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}
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if ( wave.outputs [3] )
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other_synth.offset( time, 30, wave.outputs [3] );
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update_volume();
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if ( wave.outputs [3] )
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other_synth.offset( time, -30, wave.outputs [3] );
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// oscs will update with new amplitude when next run
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}
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else if ( addr == 0xFF25 || addr == status_reg )
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{
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int mask = (regs [status_reg - start_addr] & 0x80) ? ~0 : 0;
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int flags = regs [0xFF25 - start_addr] & mask;
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// left/right assignments
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for ( int i = 0; i < osc_count; i++ )
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{
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Gb_Osc& osc = *oscs [i];
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osc.enabled &= mask;
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int bits = flags >> i;
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Blip_Buffer* old_output = osc.output;
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osc.output_select = (bits >> 3 & 2) | (bits & 1);
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osc.output = osc.outputs [osc.output_select];
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if ( osc.output != old_output )
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{
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int amp = osc.last_amp;
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osc.last_amp = 0;
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if ( amp && old_output )
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other_synth.offset( time, -amp, old_output );
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}
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}
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if ( addr == status_reg && data != old_reg )
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{
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if ( !(data & 0x80) )
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{
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for ( unsigned i = 0; i < sizeof powerup_regs; i++ )
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{
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if ( i != status_reg - start_addr )
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write_register( time, i + start_addr, powerup_regs [i] );
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}
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}
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else
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{
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//debug_printf( "APU powered on\n" );
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}
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}
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}
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else if ( addr >= 0xFF30 )
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{
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int index = (addr & 0x0F) * 2;
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wave.wave [index] = data >> 4;
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wave.wave [index + 1] = data & 0x0F;
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}
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}
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int Gb_Apu::read_register( blip_time_t time, unsigned addr )
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{
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run_until( time );
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int index = addr - start_addr;
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require( (unsigned) index < register_count );
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int data = regs [index];
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if ( addr == status_reg )
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{
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data = (data & 0x80) | 0x70;
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for ( int i = 0; i < osc_count; i++ )
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{
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const Gb_Osc& osc = *oscs [i];
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if ( osc.enabled && (osc.length || !(osc.regs [4] & osc.len_enabled_mask)) )
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data |= 1 << i;
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}
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}
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return data;
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}
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