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/* ay.c: AY-8-3912 routines
Copyright (c) 1999-2009 Philip Kendall
$Id: ay.c 4030 2009-06-07 14:38:38Z fredm $
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.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
Author contact information:
E-mail: philip-fuse@shadowmagic.org.uk
*/
#include <config.h>
#include <string.h>
#include "compat.h"
#include "machine.h"
#include "module.h"
#include "printer.h"
#include "psg.h"
#include "sound.h"
/* Unused bits in the AY registers are silently zeroed out; these masks
accomplish this */
static const libspectrum_byte mask[ AY_REGISTERS ] = {
0xff, 0x0f, 0xff, 0x0f, 0xff, 0x0f, 0x1f, 0xff,
0x1f, 0x1f, 0x1f, 0xff, 0xff, 0x0f, 0xff, 0xff,
};
static void ay_reset( int hard_reset );
static void ay_from_snapshot( libspectrum_snap *snap );
static void ay_to_snapshot( libspectrum_snap *snap );
static module_info_t ay_module_info = {
ay_reset,
NULL,
NULL,
ay_from_snapshot,
ay_to_snapshot,
};
int
ay_init( void )
{
module_register( &ay_module_info );
return 0;
}
static void
ay_reset( int hard_reset GCC_UNUSED )
{
ayinfo *ay = &machine_current->ay;
ay->current_register = 0;
memset( ay->registers, 0, sizeof( ay->registers ) );
}
/* What happens when the AY register port (traditionally 0xfffd on the 128K
machines) is read from */
libspectrum_byte
ay_registerport_read( libspectrum_word port GCC_UNUSED, int *attached )
{
int current;
const libspectrum_byte port_input = 0xbf; /* always allow serial output */
*attached = 1;
current = machine_current->ay.current_register;
/* The AY I/O ports return input directly from the port when in
input mode; but in output mode, they return an AND between the
register value and the port input. So, allow for this when
reading R14... */
if( current == 14 ) {
if(machine_current->ay.registers[7] & 0x40)
return (port_input & machine_current->ay.registers[14]);
else
return port_input;
}
/* R15 is simpler to do, as the 8912 lacks the second I/O port, and
the input-mode input is always 0xff */
if( current == 15 && !( machine_current->ay.registers[7] & 0x80 ) )
return 0xff;
/* Otherwise return register value, appropriately masked */
return machine_current->ay.registers[ current ] & mask[ current ];
}
/* And when it's written to */
void
ay_registerport_write( libspectrum_word port GCC_UNUSED, libspectrum_byte b )
{
machine_current->ay.current_register = (b & 15);
}
/* What happens when the AY data port (traditionally 0xbffd on the 128K
machines) is written to; no corresponding read function as this
always returns 0xff */
void
ay_dataport_write( libspectrum_word port GCC_UNUSED, libspectrum_byte b )
{
int current;
current = machine_current->ay.current_register;
machine_current->ay.registers[ current ] = b & mask[ current ];
sound_ay_write( current, b, tstates );
if( psg_recording ) psg_write_register( current, b );
if( current == 14 ) printer_serial_write( b );
}
void
ay_state_from_snapshot( libspectrum_snap *snap )
{
size_t i;
ay_registerport_write( 0xfffd,
libspectrum_snap_out_ay_registerport( snap ) );
for( i = 0; i < AY_REGISTERS; i++ ) {
machine_current->ay.registers[i] =
libspectrum_snap_ay_registers( snap, i );
sound_ay_write( i, machine_current->ay.registers[i], 0 );
}
}
static void
ay_from_snapshot( libspectrum_snap *snap )
{
if( machine_current->capabilities & LIBSPECTRUM_MACHINE_CAPABILITY_AY ) {
ay_state_from_snapshot( snap );
}
}
static void
ay_to_snapshot( libspectrum_snap *snap )
{
size_t i;
libspectrum_snap_set_out_ay_registerport(
snap, machine_current->ay.current_register
);
for( i = 0; i < AY_REGISTERS; i++ )
libspectrum_snap_set_ay_registers( snap, i,
machine_current->ay.registers[i] );
}
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