mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
synced 2024-11-09 12:25:16 +01:00
406 lines
10 KiB
C
406 lines
10 KiB
C
/***************************************************************************************
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* Genesis Plus 1.2a
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* Main Emulation
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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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****************************************************************************************/
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#include "shared.h"
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#define CLOCK_NTSC 53693175
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#define CLOCK_PAL 53203424
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#define SND_SIZE (snd.buffer_size * sizeof(int16))
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/* Global variables */
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t_bitmap bitmap;
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t_snd snd;
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uint8 vdp_rate;
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uint16 lines_per_frame;
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double Master_Clock;
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uint32 aim_m68k;
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uint32 count_m68k;
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uint32 line_m68k;
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uint32 hint_m68k;
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uint32 aim_z80;
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uint32 count_z80;
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uint32 line_z80;
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int32 current_z80;
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uint8 odd_frame;
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uint8 interlaced;
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uint8 system_hw;
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static inline void audio_update (void);
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/****************************************************************
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* Virtual Genesis initialization
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****************************************************************/
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void system_init (void)
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{
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/* PAL/NTSC timings */
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vdp_rate = vdp_pal ? 50 : 60;
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lines_per_frame = vdp_pal ? 313 : 262;
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Master_Clock = vdp_pal ? (double)CLOCK_PAL : (double)CLOCK_NTSC;
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gen_init ();
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vdp_init ();
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render_init ();
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cart_hw_init();
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}
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/****************************************************************
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* Virtual Genesis Restart
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****************************************************************/
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void system_reset (void)
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{
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aim_m68k = 0;
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count_m68k = 0;
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line_m68k = 0;
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aim_z80 = 0;
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count_z80 = 0;
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line_z80 = 0;
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current_z80 = 0;
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odd_frame = 0;
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interlaced = 0;
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/* Cart Hardware reset */
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cart_hw_reset();
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/* Hard reset */
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gen_reset (1);
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vdp_reset ();
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render_reset ();
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io_reset();
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SN76489_Reset(0);
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/* Sound buffers reset */
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memset (snd.psg.buffer, 0, SND_SIZE);
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memset (snd.fm.buffer[0], 0, SND_SIZE*2);
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memset (snd.fm.buffer[1], 0, SND_SIZE*2);
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}
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/****************************************************************
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* Virtual Genesis shutdown
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****************************************************************/
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void system_shutdown (void)
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{
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gen_shutdown ();
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vdp_shutdown ();
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render_shutdown ();
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}
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/****************************************************************
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* Virtual Genesis Frame emulation
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****************************************************************/
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int system_frame (int do_skip)
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{
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if (!gen_running)
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{
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update_input();
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return 0;
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}
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/* reset cycles counts */
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count_m68k = 0;
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aim_m68k = 0;
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aim_z80 = 0;
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count_z80 = 0;
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fifo_write_cnt = 0;
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fifo_lastwrite = 0;
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/* update display settings */
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int line;
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int reset = resetline;
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int vdp_height = bitmap.viewport.h;
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int end_line = vdp_height + bitmap.viewport.y;
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int start_line = lines_per_frame - bitmap.viewport.y;
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int old_interlaced = interlaced;
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interlaced = (reg[12] >> 1) & 3;
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if (old_interlaced != interlaced)
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{
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bitmap.viewport.changed = 2;
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im2_flag = (interlaced == 3);
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odd_frame = 1;
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}
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odd_frame ^= 1;
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/* update VDP status */
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status &= 0xFFF5; // clear VBLANK and DMA flags
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if (odd_frame && interlaced) status |= 0x0010; // even/odd field flag (interlaced modes only)
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else status &= 0xFFEF;
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/* Reload H Counter */
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int h_counter = reg[10];
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/* parse sprites for line 0 (done on last line) */
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parse_satb (0x80);
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/* Line processing */
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for (line = 0; line < lines_per_frame; line ++)
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{
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/* Update VCounter */
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v_counter = line;
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/* 6-Buttons or Menacer update */
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input_update();
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/* Update CPU cycle counters */
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hint_m68k = count_m68k;
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line_m68k = aim_m68k;
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line_z80 = aim_z80;
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aim_z80 += z80cycles_per_line;
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aim_m68k += m68cycles_per_line;
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/* Soft Reset ? */
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if (line == reset)
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{
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#ifdef NGC
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/* wait for RESET button to be released */
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if (!SYS_ResetButtonDown())
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#endif
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gen_reset(0);
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}
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/* Horizontal Interrupt */
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if (line <= vdp_height)
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{
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if(--h_counter < 0)
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{
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h_counter = reg[10];
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hint_pending = 1;
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if (reg[0] & 0x10) irq_status = (irq_status & 0xff) | 0x14;
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/* adjust timings to take further decrement in account (see below) */
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if ((line != 0) || (h_counter == 0)) aim_m68k += 36;
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}
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/* HINT will be triggered on next line, approx. 36 cycles before VDP starts line rendering */
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/* during this period, any VRAM/CRAM/VSRAM writes should NOT be taken in account before next line */
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/* as a result, current line is shortened */
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/* fix Lotus 1, Lotus 2 RECS, Striker, Zero the Kamikaze Squirell */
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if ((line < vdp_height) && (h_counter == 0)) aim_m68k -= 36;
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/* update DMA timings */
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if (dma_length) dma_update();
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/* Vertical Retrace */
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if (line == vdp_height)
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{
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/* render overscan */
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if ((line < end_line) && (!do_skip)) render_line(line, 1);
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/* update inputs */
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update_input();
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/* set VBLANK flag */
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status |= 0x08;
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/* Z80 interrupt is 16ms period (one frame) and 64us length (one scanline) */
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zirq = 1;
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z80_set_irq_line(0, ASSERT_LINE);
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/* delay between HINT, VBLANK and VINT (Dracula, OutRunners, VR Troopers) */
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m68k_run(line_m68k + 84);
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if (zreset && !zbusreq)
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{
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current_z80 = line_z80 + 39 - count_z80;
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if (current_z80 > 0) count_z80 += z80_execute(current_z80);
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}
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else count_z80 = line_z80 + 39;
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/* Vertical Interrupt */
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status |= 0x80;
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vint_pending = 1;
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if (reg[1] & 0x20) irq_status = (irq_status & 0xff) | 0x2416; // 36 cycles latency after VINT occurence flag (Ex-Mutants, Tyrant)
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}
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else if (!do_skip)
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{
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/* render scanline and parse sprites for line n+1 */
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render_line(line, 0);
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if (line < (vdp_height-1)) parse_satb(0x81 + line);
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}
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}
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else
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{
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/* update DMA timings */
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if (dma_length) dma_update();
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/* render overscan */
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if ((line < end_line) || (line >= start_line))
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{
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if (!do_skip) render_line(line, 1);
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}
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/* clear any pending Z80 interrupt */
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if (zirq)
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{
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zirq = 0;
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z80_set_irq_line(0, CLEAR_LINE);
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}
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}
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/* Process line */
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m68k_run(aim_m68k);
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if (zreset == 1 && zbusreq == 0)
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{
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current_z80 = aim_z80 - count_z80;
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if (current_z80 > 0) count_z80 += z80_execute(current_z80);
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}
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else count_z80 = aim_z80;
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/* SVP chip */
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if (svp) ssp1601_run(SVP_cycles);
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}
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audio_update ();
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return gen_running;
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}
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/****************************************************************
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* Audio System
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****************************************************************/
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int audio_init (int rate)
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{
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/* Shutdown first */
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audio_shutdown();
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/* Clear the sound data context */
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memset (&snd, 0, sizeof (snd));
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/* Make sure the requested sample rate is valid */
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if (!rate || ((rate < 8000) | (rate > 48000))) return (-1);
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snd.sample_rate = rate;
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/* Calculate the sound buffer size (for one frame) */
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snd.buffer_size = (rate / vdp_rate);
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#ifdef DOS
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/* output buffers */
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snd.buffer[0] = (int16 *) malloc(SND_SIZE);
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snd.buffer[1] = (int16 *) malloc(SND_SIZE);
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if (!snd.buffer[0] || !snd.buffer[1]) return (-1);
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memset (snd.buffer[0], 0, SND_SIZE);
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memset (snd.buffer[1], 0, SND_SIZE);
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#endif
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/* YM2612 stream buffers */
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snd.fm.buffer[0] = (int *)malloc (SND_SIZE*2);
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snd.fm.buffer[1] = (int *)malloc (SND_SIZE*2);
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if (!snd.fm.buffer[0] || !snd.fm.buffer[1]) return (-1);
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memset (snd.fm.buffer[0], 0, SND_SIZE*2);
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memset (snd.fm.buffer[1], 0, SND_SIZE*2);
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/* SRC buffers */
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if (config.hq_fm && !config.fm_core)
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{
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snd.fm.src_out = (float *) malloc(snd.buffer_size*2*sizeof(float));
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if (!snd.fm.src_out) return (-1);
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}
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/* SN76489 stream buffers */
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snd.psg.buffer = (int16 *)malloc (SND_SIZE);
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if (!snd.psg.buffer) return (-1);
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memset (snd.psg.buffer, 0, SND_SIZE);
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/* Set audio enable flag */
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snd.enabled = 1;
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/* Initialize Sound Chips emulation */
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sound_init(rate);
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return (0);
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}
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void audio_shutdown(void)
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{
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/* free sound buffers */
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if (snd.buffer[0]) free(snd.buffer[0]);
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if (snd.buffer[1]) free(snd.buffer[1]);
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if (snd.fm.buffer[0]) free(snd.fm.buffer[0]);
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if (snd.fm.buffer[1]) free(snd.fm.buffer[1]);
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if (snd.fm.src_out) free(snd.fm.src_out);
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if (snd.psg.buffer) free(snd.psg.buffer);
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}
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static int ll, rr;
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static inline void audio_update (void)
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{
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int i;
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int l, r;
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double psg_preamp = config.psg_preamp;
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double fm_preamp = config.fm_preamp;
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int boost = config.boost;
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int filter = config.filter;
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#ifndef DOS
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int16 *sb = (int16 *) soundbuffer[mixbuffer];
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#endif
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/* get remaining samples */
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sound_update();
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/* mix samples */
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for (i = 0; i < snd.buffer_size; i ++)
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{
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l = r = (int) ((double)snd.psg.buffer[i] * psg_preamp);
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l += (int) ((double)snd.fm.buffer[0][i] * fm_preamp);
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r += (int) ((double)snd.fm.buffer[1][i] * fm_preamp);
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snd.fm.buffer[0][i] = 0;
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snd.fm.buffer[1][i] = 0;
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snd.psg.buffer[i] = 0;
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/* single-pole low-pass filter (6 dB/octave) */
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if (filter)
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{
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l = (ll + l) >> 1;
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r = (rr + r) >> 1;
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ll = l;
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rr = r;
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}
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/* boost volume if asked*/
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l = l * boost;
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r = r * boost;
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/* clipping */
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if (l > 32767) l = 32767;
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else if (l < -32768) l = -32768;
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if (r > 32767) r = 32767;
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else if (r < -32768) r = -32768;
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/* update sound buffer */
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#ifdef DOS
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snd.buffer[0][i] = l;
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snd.buffer[1][i] = r;
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#elif LSB_FIRST
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*sb++ = l;
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*sb++ = r;
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#else
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*sb++ = r;
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*sb++ = l;
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#endif
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}
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#ifndef DOS
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mixbuffer++;
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mixbuffer &= 0xf;
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#endif
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}
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