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// Game_Music_Emu 0.6-pre. http://www.slack.net/~ant/
#include "Ay_Core.h"
/* Copyright (C) 2006-2009 Shay Green. This module is free software; you
can redistribute it and/or modify it under the terms of the GNU Lesser
General Public License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version. This
module 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 Lesser General Public License for more
details. You should have received a copy of the GNU Lesser General Public
License along with this module; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
#include "blargg_source.h"
inline void Ay_Core::disable_beeper()
{
beeper_mask = 0;
last_beeper = 0;
}
Ay_Core::Ay_Core()
{
beeper_output = NULL;
disable_beeper();
}
Ay_Core::~Ay_Core() { }
void Ay_Core::set_beeper_output( Blip_Buffer* b )
{
beeper_output = b;
if ( b && !cpc_mode )
beeper_mask = 0x10;
else
disable_beeper();
}
void Ay_Core::start_track( registers_t const& r, addr_t play )
{
play_addr = play;
memset( mem_.padding1, 0xFF, sizeof mem_.padding1 );
int const mirrored = 0x80; // this much is mirrored after end of memory
memset( mem_.ram + mem_size + mirrored, 0xFF, sizeof mem_.ram - mem_size - mirrored );
memcpy( mem_.ram + mem_size, mem_.ram, mirrored ); // some code wraps around (ugh)
cpu.reset( mem_.padding1, mem_.padding1 );
cpu.map_mem( 0, mem_size, mem_.ram, mem_.ram );
cpu.r = r;
beeper_delta = (int) (apu_.amp_range * 0.8);
last_beeper = 0;
next_play = play_period;
spectrum_mode = false;
cpc_mode = false;
cpc_latch = 0;
set_beeper_output( beeper_output );
apu_.reset();
// a few tunes rely on channels having tone enabled at the beginning
apu_.write_addr( 7 );
apu_.write_data( 0, 0x38 );
}
// Emulation
void Ay_Core::cpu_out_( time_t time, addr_t addr, int data )
{
// Spectrum
if ( !cpc_mode )
{
switch ( addr & 0xFEFF )
{
case 0xFEFD:
spectrum_mode = true;
apu_.write_addr( data );
return;
case 0xBEFD:
spectrum_mode = true;
apu_.write_data( time, data );
return;
}
}
// CPC
if ( !spectrum_mode )
{
switch ( addr >> 8 )
{
case 0xF6:
switch ( data & 0xC0 )
{
case 0xC0:
apu_.write_addr( cpc_latch );
goto enable_cpc;
case 0x80:
apu_.write_data( time, cpc_latch );
goto enable_cpc;
}
break;
case 0xF4:
cpc_latch = data;
goto enable_cpc;
}
}
dprintf( "Unmapped OUT: $%04X <- $%02X\n", addr, data );
return;
enable_cpc:
if ( !cpc_mode )
{
cpc_mode = true;
disable_beeper();
set_cpc_callback.f( set_cpc_callback.data );
}
}
int Ay_Core::cpu_in( addr_t addr )
{
// keyboard read and other things
if ( (addr & 0xFF) == 0xFE )
return 0xFF; // other values break some beeper tunes
dprintf( "Unmapped IN : $%04X\n", addr );
return 0xFF;
}
void Ay_Core::end_frame( time_t* end )
{
cpu.set_time( 0 );
// Since detection of CPC mode will halve clock rate during the frame
// and thus generate up to twice as much sound, we must generate half
// as much until mode is known.
if ( !(spectrum_mode | cpc_mode) )
*end /= 2;
while ( cpu.time() < *end )
{
run_cpu( min( *end, next_play ) );
if ( cpu.time() >= next_play )
{
// next frame
next_play += play_period;
if ( cpu.r.iff1 )
{
// interrupt enabled
if ( mem_.ram [cpu.r.pc] == 0x76 )
cpu.r.pc++; // advance past HALT instruction
cpu.r.iff1 = 0;
cpu.r.iff2 = 0;
mem_.ram [--cpu.r.sp] = byte (cpu.r.pc >> 8);
mem_.ram [--cpu.r.sp] = byte (cpu.r.pc);
// fixed interrupt
cpu.r.pc = 0x38;
cpu.adjust_time( 12 );
if ( cpu.r.im == 2 )
{
// vectored interrupt
addr_t addr = cpu.r.i * 0x100 + 0xFF;
cpu.r.pc = mem_.ram [(addr + 1) & 0xFFFF] * 0x100 + mem_.ram [addr];
cpu.adjust_time( 6 );
}
}
}
}
// End time frame
*end = cpu.time();
next_play -= *end;
check( next_play >= 0 );
cpu.adjust_time( -*end );
apu_.end_frame( *end );
}
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