mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
synced 2024-09-10 16:53:15 +02:00
![ekeeke31](/assets/img/avatar_default.png)
.improved VDP FIFO timing accuracy .improved Z80 interrupt accuracy .modified CPU Hard Reset start cycles
239 lines
7.2 KiB
C
239 lines
7.2 KiB
C
/***************************************************************************************
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* Genesis Plus
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* Genesis internals & Bus controller
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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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* Eke-Eke (2007,2008,2009), additional code & fixes for the GCN/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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uint8 bios_rom[0x10000]; /* OS ROM */
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uint8 work_ram[0x10000]; /* 68K RAM */
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uint8 zram[0x2000]; /* Z80 RAM */
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uint8 zstate; /* Z80 bus state (d0 = BUSACK, d1 = /RESET) */
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uint32 zbank; /* Z80 bank window address */
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/*--------------------------------------------------------------------------*/
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/* Init, reset, shutdown functions */
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/*--------------------------------------------------------------------------*/
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void gen_init(void)
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{
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int i;
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/* initialize CPUs */
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m68k_set_cpu_type(M68K_CPU_TYPE_68000);
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m68k_init();
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z80_init(0,0,0,z80_irq_callback);
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/* initialize 68k mapped memory */
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/* $000000-$7fffff is affected to cartridge area (see cart_hw.c) */
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/* $800000-$ffffff is affected to WRAM (see VDP DMA) */
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for (i=0x80; i<0x100; i++)
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{
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m68k_memory_map[i].base = work_ram;
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m68k_memory_map[i].read8 = NULL;
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m68k_memory_map[i].read16 = NULL;
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m68k_memory_map[i].write8 = NULL;
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m68k_memory_map[i].write16 = NULL;
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zbank_memory_map[i].read = NULL;
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zbank_memory_map[i].write = NULL;
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}
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/* initialize 68k memory handlers */
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for (i=0x80; i<0xe0; i++)
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{
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/* illegal area */
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m68k_memory_map[i].read8 = m68k_lockup_r_8;
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m68k_memory_map[i].read16 = m68k_lockup_r_16;
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m68k_memory_map[i].write8 = m68k_lockup_w_8;
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m68k_memory_map[i].write16 = m68k_lockup_w_16;
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zbank_memory_map[i].read = zbank_lockup_r;
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zbank_memory_map[i].write = zbank_lockup_w;
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}
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/* Z80 bus */
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m68k_memory_map[0xa0].read8 = z80_read_byte;
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m68k_memory_map[0xa0].read16 = z80_read_word;
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m68k_memory_map[0xa0].write8 = z80_write_byte;
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m68k_memory_map[0xa0].write16 = z80_write_word;
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zbank_memory_map[0xa0].read = zbank_lockup_r;
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zbank_memory_map[0xa0].write = zbank_lockup_w;
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/* I/O & Control registers */
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m68k_memory_map[0xa1].read8 = ctrl_io_read_byte;
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m68k_memory_map[0xa1].read16 = ctrl_io_read_word;
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m68k_memory_map[0xa1].write8 = ctrl_io_write_byte;
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m68k_memory_map[0xa1].write16 = ctrl_io_write_word;
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zbank_memory_map[0xa1].read = zbank_read_ctrl_io;
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zbank_memory_map[0xa1].write = zbank_write_ctrl_io;
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/* SEGA PICO */
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if (system_hw == SYSTEM_PICO)
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{
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m68k_memory_map[0x80].read8 = pico_read_byte;
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m68k_memory_map[0x80].read16 = pico_read_word;
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m68k_memory_map[0x80].write8 = m68k_unused_8_w;
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m68k_memory_map[0x80].write16 = m68k_unused_16_w;
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/* there is no I/O area (Notaz) */
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m68k_memory_map[0xa0].read8 = m68k_read_bus_8;
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m68k_memory_map[0xa0].read16 = m68k_read_bus_16;
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m68k_memory_map[0xa0].write8 = m68k_unused_8_w;
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m68k_memory_map[0xa0].write16 = m68k_unused_16_w;
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m68k_memory_map[0xa1].read8 = m68k_read_bus_8;
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m68k_memory_map[0xa1].read16 = m68k_read_bus_16;
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m68k_memory_map[0xa1].write8 = m68k_unused_8_w;
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m68k_memory_map[0xa1].write16 = m68k_unused_16_w;
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}
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/* VDP */
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for (i=0xc0; i<0xe0; i+=8)
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{
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m68k_memory_map[i].read8 = vdp_read_byte;
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m68k_memory_map[i].read16 = vdp_read_word;
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m68k_memory_map[i].write8 = vdp_write_byte;
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m68k_memory_map[i].write16 = vdp_write_word;
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zbank_memory_map[i].read = zbank_read_vdp;
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zbank_memory_map[i].write = zbank_write_vdp;
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}
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}
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void gen_hardreset(void)
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{
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/* Clear RAM */
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memset (work_ram, 0x00, sizeof (work_ram));
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memset (zram, 0x00, sizeof (zram));
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/* TMSS BIOS support */
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if (config.bios_enabled == 3)
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m68k_memory_map[0].base = bios_rom;
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/* Reset CPU cycles (check EA logo corruption, no glitches for Skitchin/Budokan on PAL 60hz MD2 with TMSS) */
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mcycles_68k = mcycles_z80 = (rand() % lines_per_frame) * MCYCLES_PER_LINE;
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/* Z80 bus is released & Z80 reset is asserted */
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zstate = 0;
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/* Assume default bank is $000000-$007FFF */
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zbank = 0;
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/* Reset 68k, Z80 & YM2612 */
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m68k_pulse_reset();
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z80_reset();
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YM2612ResetChip();
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}
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void gen_softreset(int state)
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{
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if (state)
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{
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/* Halt 68k, Z80 & YM2612 */
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m68k_pulse_halt();
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zstate = 0;
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YM2612ResetChip();
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}
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else
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{
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/* Reset Pro Action Replay (required in Trainer mode) */
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if (config.lock_on == TYPE_AR)
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datel_reset(0);
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/* 68k & Z80 could restart anywhere in VDP frame (fixes Eternal Champions, X-Men 2) */
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mcycles_68k = mcycles_z80 = (uint32)((MCYCLES_PER_LINE * lines_per_frame) * ((double)rand() / (double)RAND_MAX));
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/* Reset 68k, Z80 & YM2612 */
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m68k_pulse_reset();
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z80_reset();
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YM2612ResetChip();
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}
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}
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void gen_shutdown(void)
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{
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z80_exit();
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}
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/*-----------------------------------------------------------------------
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Bus controller chip functions
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-----------------------------------------------------------------------*/
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void gen_busreq_w(uint32 state, uint32 cycles)
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{
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if (state) /* Z80 Bus Requested */
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{
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/* if z80 was running, resynchronize with 68k */
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if (zstate == 1)
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z80_run(cycles);
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/* request Z80 bus */
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zstate |= 2;
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}
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else /* Z80 Bus Released */
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{
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/* if z80 is restarted, resynchronize with 68k */
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if (zstate == 3)
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mcycles_z80 = cycles;
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/* release Z80 bus */
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zstate &= 1;
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}
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}
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void gen_reset_w(uint32 state, uint32 cycles)
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{
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/* detect !ZRESET transitions */
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if (state == (zstate & 1))
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return;
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if (state) /* !ZRESET inactive */
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{
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/* if z80 is restarted, resynchronize with 68k */
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if (zstate == 0)
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mcycles_z80 = cycles;
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/* reset Z80 */
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z80_reset();
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/* negate Z80 reset */
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zstate |= 1;
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}
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else /* !ZRESET active */
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{
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/* if z80 was running, resynchronize with 68k */
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if (zstate == 1)
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z80_run(cycles);
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/* assert Z80 reset */
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zstate &= 2;
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}
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/* reset YM2612 */
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fm_reset(cycles);
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}
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void gen_bank_w (uint32 state)
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{
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zbank = ((zbank >> 1) | ((state & 1) << 23)) & 0xFF8000;
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}
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int z80_irq_callback (int param)
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{
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return 0xFF;
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}
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