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Genesis-Plus-GX/source/system.c

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/***************************************************************************************
* Genesis Plus 1.2a
* Main Emulation
*
* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Charles Mac Donald (original code)
* modified by Eke-Eke (compatibility fixes & additional code), GC/Wii port
*
* 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
*
****************************************************************************************/
#include "shared.h"
#define CLOCK_NTSC 53693175
#define CLOCK_PAL 53203424
#define SND_SIZE (snd.buffer_size * sizeof(int16))
/* Global variables */
t_bitmap bitmap;
t_snd snd;
uint8 vdp_rate;
uint16 lines_per_frame;
double Master_Clock;
uint32 aim_m68k;
uint32 count_m68k;
uint32 line_m68k;
uint32 hint_m68k;
uint32 aim_z80;
uint32 count_z80;
uint32 line_z80;
int32 current_z80;
uint8 odd_frame;
uint8 interlaced;
uint32 frame_cnt;
uint8 system_hw;
/****************************************************************
* CPU execution managment
****************************************************************/
/* Interrupt Manager
this is called before each new executed instruction
only if interrupts have been updated
*/
static inline void update_interrupts(void)
{
uint8 latency = hvint_updated;
hvint_updated = -1;
/* VDP hardware latency */
if (latency) count_m68k += m68k_execute(latency);
/* Level 6 interrupt */
if (vint_pending && (reg[1] & 0x20))
{
vint_triggered = 1;
m68k_set_irq(6);
}
/* Level 4 interrupt */
else if (hint_pending && (reg[0] & 0x10))
{
m68k_set_irq(4);
}
/* Clear all interrupts */
else
{
m68k_set_irq(0);
}
}
static inline void m68k_run (int cyc)
{
while (count_m68k < cyc)
{
/* check interrupts */
if (hvint_updated >= 0) update_interrupts();
/* execute a single instruction */
count_m68k += m68k_execute(1);
}
}
void z80_run (int cyc)
{
current_z80 = cyc - count_z80;
if (current_z80 > 0) count_z80 += z80_execute(current_z80);
}
/****************************************************************
* Virtual Genesis initialization
****************************************************************/
void system_init (void)
{
/* PAL/NTSC timings */
vdp_rate = vdp_pal ? 50 : 60;
lines_per_frame = vdp_pal ? 313 : 262;
Master_Clock = vdp_pal ? (double)CLOCK_PAL : (double)CLOCK_NTSC;
gen_init ();
vdp_init ();
render_init ();
cart_hw_init();
}
/****************************************************************
* Virtual Genesis Restart
****************************************************************/
void system_reset (void)
{
aim_m68k = 0;
count_m68k = 0;
line_m68k = 0;
aim_z80 = 0;
count_z80 = 0;
line_z80 = 0;
current_z80 = 0;
odd_frame = 0;
interlaced = 0;
frame_cnt = 0;
/* Cart Hardware reset */
cart_hw_reset();
/* Hard reset */
gen_reset (1);
vdp_reset ();
render_reset ();
io_reset();
SN76489_Reset(0);
/* Sound buffers reset */
memset (snd.psg.buffer, 0, SND_SIZE);
memset (snd.fm.buffer[0], 0, SND_SIZE*2);
memset (snd.fm.buffer[1], 0, SND_SIZE*2);
}
/****************************************************************
* Virtual Genesis shutdown
****************************************************************/
void system_shutdown (void)
{
gen_shutdown ();
vdp_shutdown ();
render_shutdown ();
}
/****************************************************************
* Virtual Genesis Frame emulation
****************************************************************/
int system_frame (int do_skip)
{
int line;
/* reset cycles counts */
count_m68k = 0;
aim_m68k = 0;
aim_z80 = 0;
count_z80 = 0;
fifo_write_cnt = 0;
fifo_lastwrite = 0;
/* increment frame counter */
frame_cnt ++;
if (!gen_running)
{
update_input();
return 0;
}
/* Clear VBLANK & DMA BUSY flags */
status &= 0xFFF5;
/* Look for interlace mode change */
uint8 old_interlaced = interlaced;
interlaced = (reg[12] & 2) >> 1;
if (old_interlaced != interlaced)
{
bitmap.viewport.changed = 2;
im2_flag = ((reg[12] & 6) == 6) ? 1 : 0;
odd_frame = 1;
}
/* Toggle even/odd field flag (interlaced modes only) */
odd_frame ^= 1;
if (odd_frame && interlaced) status |= 0x0010;
else status &= 0xFFEF;
/* Reset HCounter */
h_counter = reg[10];
/* Parse sprites for line 0 (done on line 261 or 312) */
parse_satb (0x80);
/* Line processing */
for (line = 0; line < lines_per_frame; line ++)
{
/* Update VCounter */
v_counter = line;
/* 6-Buttons or Menacer update */
input_update();
/* Update CPU cycle counters */
hint_m68k = count_m68k;
line_m68k = aim_m68k;
line_z80 = aim_z80;
aim_z80 += z80cycles_per_line;
aim_m68k += m68cycles_per_line;
/* Check "soft reset" */
if (line == resetline)
{
#ifdef NGC
/* wait for RESET button to be released */
if (!SYS_ResetButtonDown())
#endif
gen_reset(0);
}
/* Horizontal Interrupt */
if (line <= bitmap.viewport.h)
{
if(--h_counter < 0)
{
h_counter = reg[10];
hint_pending = 1;
hvint_updated = 0;
/* adjust timings to take decrement in account */
if ((line != 0) || (h_counter == 0)) aim_m68k += 36;
}
/* HINT will be triggered on next line, approx. 36 cycles before VDP starts line rendering */
/* during this period, any VRAM/CRAM/VSRAM writes should NOT be taken in account before next line */
/* as a result, current line is shortened */
/* fix Lotus 1, Lotus 2 RECS, Striker, Zero the Kamikaze Squirell */
if ((line < bitmap.viewport.h)&&(h_counter == 0)) aim_m68k -= 36;
}
/* Check if there is any DMA in progess */
if (dma_length) dma_update();
/* Render Line */
if (!do_skip)
{
render_line(line,odd_frame);
if (line < (bitmap.viewport.h-1)) parse_satb(0x81 + line);
}
/* Vertical Retrace */
if (line == bitmap.viewport.h)
{
/* update inputs */
update_input();
/* set VBLANK flag */
status |= 0x08;
/* Z80 interrupt is 16ms period (one frame) and 64us length (one scanline) */
zirq = 1;
z80_set_irq_line(0, ASSERT_LINE);
/* delay between HINT, VBLANK and VINT (Dracula, OutRunners, VR Troopers) */
m68k_run(line_m68k + 84);
if (zreset && !zbusreq) z80_run(line_z80 + 39);
else count_z80 = line_z80 + 39;
/* Vertical Interrupt */
status |= 0x80;
vint_pending = 1;
hvint_updated = 36; /* Tyrants, Mega-Lo-Mania & Ex Mutant need some cycles to read VINT flag */
}
else if (zirq)
{
/* clear any pending Z80 interrupt */
zirq = 0;
z80_set_irq_line(0, CLEAR_LINE);
}
/* Process line */
m68k_run(aim_m68k);
if (zreset == 1 && zbusreq == 0) z80_run(aim_z80);
else count_z80 = aim_z80;
/* SVP chip */
if (svp) ssp1601_run(SVP_cycles);
}
audio_update ();
return gen_running;
}
/****************************************************************
* Audio System
****************************************************************/
int audio_init (int rate)
{
/* Shutdown first */
audio_shutdown();
/* Clear the sound data context */
memset (&snd, 0, sizeof (snd));
/* Make sure the requested sample rate is valid */
if (!rate || ((rate < 8000) | (rate > 48000))) return (-1);
snd.sample_rate = rate;
/* Calculate the sound buffer size (for one frame) */
snd.buffer_size = (rate / vdp_rate);
#ifdef DOS
/* output buffers */
snd.buffer[0] = (int16 *) malloc(SND_SIZE);
snd.buffer[1] = (int16 *) malloc(SND_SIZE);
if (!snd.buffer[0] || !snd.buffer[1]) return (-1);
memset (snd.buffer[0], 0, SND_SIZE);
memset (snd.buffer[1], 0, SND_SIZE);
#endif
/* YM2612 stream buffers */
snd.fm.buffer[0] = (int *)malloc (SND_SIZE*2);
snd.fm.buffer[1] = (int *)malloc (SND_SIZE*2);
if (!snd.fm.buffer[0] || !snd.fm.buffer[1]) return (-1);
memset (snd.fm.buffer[0], 0, SND_SIZE*2);
memset (snd.fm.buffer[1], 0, SND_SIZE*2);
/* SRC buffers */
if (config.hq_fm && !config.fm_core)
{
snd.fm.src_out = (float *) malloc(snd.buffer_size*2*sizeof(float));
if (!snd.fm.src_out) return (-1);
}
/* SN76489 stream buffers */
snd.psg.buffer = (int16 *)malloc (SND_SIZE);
if (!snd.psg.buffer) return (-1);
memset (snd.psg.buffer, 0, SND_SIZE);
/* Set audio enable flag */
snd.enabled = 1;
/* Initialize Sound Chips emulation */
sound_init(rate);
return (0);
}
void audio_shutdown(void)
{
/* free sound buffers */
if (snd.buffer[0]) free(snd.buffer[0]);
if (snd.buffer[1]) free(snd.buffer[1]);
if (snd.fm.buffer[0]) free(snd.fm.buffer[0]);
if (snd.fm.buffer[1]) free(snd.fm.buffer[1]);
if (snd.fm.src_out) free(snd.fm.src_out);
if (snd.psg.buffer) free(snd.psg.buffer);
}
static int ll, rr;
void audio_update (void)
{
int i;
int l, r;
double psg_preamp = config.psg_preamp;
double fm_preamp = config.fm_preamp;
int boost = config.boost;
int filter = config.filter;
#ifndef DOS
int16 *sb = (int16 *) soundbuffer[mixbuffer];
#endif
/* get remaining samples */
sound_update();
/* mix samples */
for (i = 0; i < snd.buffer_size; i ++)
{
l = r = (int) ((double)snd.psg.buffer[i] * psg_preamp);
l += (int) ((double)snd.fm.buffer[0][i] * fm_preamp);
r += (int) ((double)snd.fm.buffer[1][i] * fm_preamp);
snd.fm.buffer[0][i] = 0;
snd.fm.buffer[1][i] = 0;
snd.psg.buffer[i] = 0;
/* single-pole low-pass filter (6 dB/octave) */
if (filter)
{
l = (ll + l) >> 1;
r = (rr + r) >> 1;
ll = l;
rr = r;
}
/* boost volume if asked*/
l = l * boost;
r = r * boost;
/* clipping */
if (l > 32767) l = 32767;
else if (l < -32768) l = -32768;
if (r > 32767) r = 32767;
else if (r < -32768) r = -32768;
/* update sound buffer */
#ifdef DOS
snd.buffer[0][i] = l;
snd.buffer[1][i] = r;
#elif LSB_FIRST
*sb++ = l;
*sb++ = r;
#else
*sb++ = r;
*sb++ = l;
#endif
}
#ifndef DOS
mixbuffer++;
mixbuffer &= 0xf;
#endif
}
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