mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
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132 lines
4.0 KiB
C
132 lines
4.0 KiB
C
/***************************************************************************************
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* Genesis Plus 1.2a
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*
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* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Charles Mac Donald (original code)
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* modified by Eke-Eke (compatibility fixes & additional code), GC/Wii port
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; 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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*
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* Sound Hardware
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****************************************************************************************/
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#include "shared.h"
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/* cycle-accurate samples */
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static int m68cycles_per_sample[2];
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/* return the number of samples that should have been rendered so far */
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static inline uint32 fm_sample_cnt(uint8 is_z80)
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{
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if (is_z80) return ((count_z80 + current_z80 - z80_ICount) * 15) / (m68cycles_per_sample[0] * 7);
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else return (count_m68k / m68cycles_per_sample[0]);
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}
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static inline uint32 psg_sample_cnt(uint8 is_z80)
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{
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if (is_z80) return ((count_z80 + current_z80 - z80_ICount) * 15) / (m68cycles_per_sample[1] * 7);
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else return (count_m68k / m68cycles_per_sample[1]);
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}
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/* update FM samples */
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static inline void fm_update()
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{
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if(snd.fm.curStage - snd.fm.lastStage > 0)
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{
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int *tempBuffer[2];
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tempBuffer[0] = snd.fm.buffer[0] + snd.fm.lastStage;
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tempBuffer[1] = snd.fm.buffer[1] + snd.fm.lastStage;
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YM2612UpdateOne(tempBuffer, snd.fm.curStage - snd.fm.lastStage);
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snd.fm.lastStage = snd.fm.curStage;
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}
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}
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/* update PSG samples */
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static inline void psg_update()
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{
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if(snd.psg.curStage - snd.psg.lastStage > 0)
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{
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int16 *tempBuffer = snd.psg.buffer + snd.psg.lastStage;
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SN76489_Update (0, tempBuffer, snd.psg.curStage - snd.psg.lastStage);
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snd.psg.lastStage = snd.psg.curStage;
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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 */
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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 */
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m68cycles_per_sample[0] = (int)(((double)m68cycles_per_line * (double)lines_per_frame * (double)vdp_rate / (double)rate) + 0.5);
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m68cycles_per_sample[1] = m68cycles_per_sample[0];
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/* YM2612 is emulated at original frequency (VLCK/144) */
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if (config.hq_fm)
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{
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m68cycles_per_sample[0] = 144;
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}
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/* initialize sound chips */
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SN76489_Init(0, (int)zclk, rate);
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SN76489_Config(0, MUTE_ALLON, VOL_FULL, FB_SEGAVDP, SRW_SEGAVDP, 0);
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YM2612Init ((int)vclk, rate);
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}
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void sound_update(int fm_len, int psg_len)
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{
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/* finalize sound buffers */
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snd.fm.curStage = fm_len;
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snd.psg.curStage = psg_len;
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/* update last samples (if needed) */
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fm_update();
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psg_update();
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/* reset samples count */
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snd.fm.curStage = 0;
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snd.fm.lastStage = 0;
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snd.psg.curStage = 0;
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snd.psg.lastStage = 0;
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}
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/* write FM chip */
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void fm_write(unsigned int cpu, unsigned int address, unsigned int data)
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{
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if (address & 1)
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{
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snd.fm.curStage = fm_sample_cnt(cpu);
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fm_update();
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}
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YM2612Write(address, data);
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}
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/* read FM status */
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unsigned int fm_read(unsigned int cpu, unsigned int address)
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{
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snd.fm.curStage = fm_sample_cnt(cpu);
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fm_update();
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return YM2612Read();
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}
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/* PSG write */
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void psg_write(unsigned int cpu, unsigned int data)
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{
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snd.psg.curStage = psg_sample_cnt(cpu);
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psg_update();
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SN76489_Write(0, data);
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}
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