Genesis-Plus-GX/source/sound/sound.c

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/***************************************************************************************
* Genesis Plus
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*
* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Charles Mac Donald (original code)
* Eke-Eke (2007,2008,2009), additional code & fixes for the GCN/Wii port
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*
* 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
*
* Sound Hardware
****************************************************************************************/
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#include "shared.h"
#include "Fir_Resampler.h"
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/* cycle-accurate samples */
static int m68cycles_per_sample[2];
/* return the number of samples that should be retrieved */
static inline int fm_sample_cnt(uint8 z80)
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{
if (z80) return ((((count_z80 + current_z80 - z80_ICount) * 15) / (m68cycles_per_sample[0] * 7)) - snd.fm.pos);
else return ((count_m68k / m68cycles_per_sample[0]) - snd.fm.pos);
}
static inline int psg_sample_cnt(uint8 z80)
{
if (z80) return ((((count_z80 + current_z80 - z80_ICount) * 15) / (m68cycles_per_sample[1] * 7)) - snd.psg.pos);
else return ((count_m68k / m68cycles_per_sample[1]) - snd.psg.pos);
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}
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/* update FM samples */
static inline void fm_update(int cnt)
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{
if (cnt > 0)
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{
YM2612Update(cnt);
snd.fm.pos += cnt;
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}
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}
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/* update PSG samples */
static inline void psg_update(int cnt)
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{
if (cnt > 0)
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{
SN76489_Update(snd.psg.buffer + snd.psg.pos, cnt);
snd.psg.pos += cnt;
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}
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}
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void sound_init(int rate)
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{
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double vclk = (vdp_pal ? (double)CLOCK_PAL : (double)CLOCK_NTSC) / 7.0; /* 68000 and YM2612 clock */
double zclk = (vdp_pal ? (double)CLOCK_PAL : (double)CLOCK_NTSC) / 15.0; /* Z80 and SN76489 clock */
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/* cycle-accurate FM & PSG samples */
m68cycles_per_sample[0] = (int)(((double)m68cycles_per_line * (double)lines_per_frame * (double)vdp_rate / (double)rate) + 0.5);
m68cycles_per_sample[1] = m68cycles_per_sample[0];
/* YM2612 is emulated at its original frequency (VLCK/144) */
if (config.hq_fm)
{
m68cycles_per_sample[0] = 144;
Fir_Resampler_time_ratio(vclk/144.0/(double)rate);
}
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/* initialize sound chips */
SN76489_Init((int)zclk,rate);
YM2612Init((int)vclk,rate);
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}
void sound_update(int fm_len, int psg_len)
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{
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/* update last samples (if needed) */
fm_update(fm_len - snd.fm.pos);
psg_update(psg_len - snd.psg.pos);
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/* reset samples count */
snd.fm.pos = 0;
snd.psg.pos = 0;
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}
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/* write FM chip */
void fm_write(unsigned int cpu, unsigned int address, unsigned int data)
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{
if (address & 1) fm_update(fm_sample_cnt(cpu));
YM2612Write(address, data);
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}
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/* read FM status */
unsigned int fm_read(unsigned int cpu, unsigned int address)
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{
fm_update(fm_sample_cnt(cpu));
return YM2612Read();
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}
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/* PSG write */
void psg_write(unsigned int cpu, unsigned int data)
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{
psg_update(psg_sample_cnt(cpu));
SN76489_Write(data);
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}