Genesis-Plus-GX/source/genesis.c

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/***************************************************************************************
* Genesis Plus
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* Genesis internals & Bus controller
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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
*
****************************************************************************************/
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#include "shared.h"
uint8 tmss[4]; /* TMSS security register */
uint8 bios_rom[0x800]; /* OS ROM */
uint8 work_ram[0x10000]; /* 68K RAM */
uint8 zram[0x2000]; /* Z80 RAM */
uint32 zbank; /* Z80 bank window address */
uint8 zstate; /* Z80 bus state (d0 = BUSACK, d1 = /RESET) */
/* PICO data */
uint8 pico_current;
uint8 pico_page[7];
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/*--------------------------------------------------------------------------*/
/* Init, reset, shutdown functions */
/*--------------------------------------------------------------------------*/
void gen_init(void)
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{
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int i;
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/* initialize CPUs */
m68k_set_cpu_type(M68K_CPU_TYPE_68000);
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m68k_init();
z80_init(0,0,0,z80_irq_callback);
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/* initialize 68k mapped memory */
/* $000000-$7fffff is affected to cartridge area (see cart_hw.c) */
/* $800000-$ffffff is affected to WRAM (see VDP DMA) */
for (i=0x80; i<0x100; i++)
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{
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m68k_memory_map[i].base = work_ram;
m68k_memory_map[i].read8 = NULL;
m68k_memory_map[i].read16 = NULL;
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;
zbank_memory_map[i].write = NULL;
}
/* initialize 68k memory handlers */
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for (i=0x80; i<0xe0; i++)
{
/* illegal area */
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m68k_memory_map[i].read8 = m68k_lockup_r_8;
m68k_memory_map[i].read16 = m68k_lockup_r_16;
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;
zbank_memory_map[i].write = zbank_lockup_w;
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}
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/* Z80 bus (bank access) */
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zbank_memory_map[0xa0].read = zbank_lockup_r;
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;
m68k_memory_map[0xa1].read16 = ctrl_io_read_word;
m68k_memory_map[0xa1].write8 = ctrl_io_write_byte;
m68k_memory_map[0xa1].write16 = ctrl_io_write_word;
zbank_memory_map[0xa1].read = zbank_read_ctrl_io;
zbank_memory_map[0xa1].write = zbank_write_ctrl_io;
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/* VDP (initially locked on models with TMSS) */
if (!(config.tmss & 1))
{
for (i=0xc0; i<0xe0; i+=8)
{
m68k_memory_map[i].read8 = vdp_read_byte;
m68k_memory_map[i].read16 = vdp_read_word;
m68k_memory_map[i].write8 = vdp_write_byte;
m68k_memory_map[i].write16 = vdp_write_word;
zbank_memory_map[i].read = zbank_read_vdp;
zbank_memory_map[i].write = zbank_write_vdp;
}
}
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/* SEGA PICO */
if (system_hw == SYSTEM_PICO)
{
m68k_memory_map[0x80].read8 = pico_read_byte;
m68k_memory_map[0x80].read16 = pico_read_word;
m68k_memory_map[0x80].write8 = m68k_unused_8_w;
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[0xa1].read8 = m68k_read_bus_8;
m68k_memory_map[0xa1].read16 = m68k_read_bus_16;
m68k_memory_map[0xa1].write8 = m68k_unused_8_w;
m68k_memory_map[0xa1].write16 = m68k_unused_16_w;
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/* page registers */
pico_current = 0x00;
pico_page[0] = 0x00;
pico_page[1] = 0x01;
pico_page[2] = 0x03;
pico_page[3] = 0x07;
pico_page[4] = 0x0F;
pico_page[5] = 0x1F;
pico_page[6] = 0x3F;
}
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}
void gen_hardreset(void)
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{
/* Clear RAM */
memset (work_ram, 0x00, sizeof (work_ram));
memset (zram, 0x00, sizeof (zram));
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/* TMSS + OS ROM support */
memset(tmss, 0x00, sizeof(tmss));
if (config.tmss == 3)
m68k_memory_map[0].base = bios_rom;
/* Reset CPU cycles (check EA logo corruption, no glitches for Skitchin/Budokan on PAL 60hz MD2 with TMSS) */
mcycles_68k = mcycles_z80 = (rand() % lines_per_frame) * MCYCLES_PER_LINE;
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/* Z80 bus is released & Z80 reset is asserted */
zstate = 0;
m68k_memory_map[0xa0].read8 = m68k_read_bus_8;
m68k_memory_map[0xa0].read16 = m68k_read_bus_16;
m68k_memory_map[0xa0].write8 = m68k_unused_8_w;
m68k_memory_map[0xa0].write16 = m68k_unused_16_w;
/* Assume default bank is $000000-$007FFF */
zbank = 0;
/* Reset 68k, Z80 & YM2612 */
m68k_pulse_reset();
z80_reset();
YM2612ResetChip();
}
void gen_softreset(int state)
{
if (state)
{
/* Halt 68k, Z80 & YM2612 */
m68k_pulse_halt();
zstate = 0;
YM2612ResetChip();
}
else
{
/* Reset Pro Action Replay (required in Trainer mode) */
if (config.lock_on == TYPE_AR)
datel_reset(0);
/* 68k & Z80 could restart anywhere in VDP frame (fixes Eternal Champions, X-Men 2) */
mcycles_68k = mcycles_z80 = (uint32)((MCYCLES_PER_LINE * lines_per_frame) * ((double)rand() / (double)RAND_MAX));
/* Reset 68k, Z80 & YM2612 */
m68k_pulse_reset();
z80_reset();
YM2612ResetChip();
}
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}
void gen_shutdown(void)
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{
z80_exit();
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}
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/*-----------------------------------------------------------------------
OS ROM / TMSS register control functions
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-----------------------------------------------------------------------*/
void gen_tmss_w(unsigned int offset, unsigned int data)
{
/* write TMSS regisiter */
WRITE_WORD(tmss, offset, data);
/* VDP requires "SEGA" value to be written in TMSSS register */
int i;
if (strncmp((char *)tmss, "SEGA", 4) == 0)
{
for (i=0xc0; i<0xe0; i+=8)
{
m68k_memory_map[i].read8 = vdp_read_byte;
m68k_memory_map[i].read16 = vdp_read_word;
m68k_memory_map[i].write8 = vdp_write_byte;
m68k_memory_map[i].write16 = vdp_write_word;
zbank_memory_map[i].read = zbank_read_vdp;
zbank_memory_map[i].write = zbank_write_vdp;
}
}
else
{
for (i=0xc0; i<0xe0; i+=8)
{
m68k_memory_map[i].read8 = m68k_lockup_r_8;
m68k_memory_map[i].read16 = m68k_lockup_r_16;
m68k_memory_map[i].write8 = m68k_lockup_w_8;
m68k_memory_map[i].write16 = m68k_lockup_w_16;
zbank_memory_map[i].read = zbank_lockup_r;
zbank_memory_map[i].write = zbank_lockup_w;
}
}
}
void gen_bankswitch_w(unsigned int data)
{
/* BIOS has not been loaded yet */
if (!(config.tmss & 2))
{
config.tmss |= 2;
memcpy(bios_rom, cart.rom, 0x800);
memset(cart.rom, 0xff, cart.romsize);
}
if (data & 1)
{
/* enable CART */
m68k_memory_map[0].base = cart.base;
}
else
{
/* enable internal BIOS ROM */
m68k_memory_map[0].base = bios_rom;
}
}
unsigned int gen_bankswitch_r(void)
{
return (m68k_memory_map[0].base == cart.base);
}
/*-----------------------------------------------------------------------
Z80 Bus controller chip functions
-----------------------------------------------------------------------*/
void gen_zbusreq_w(unsigned int state, unsigned int cycles)
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{
if (state) /* Z80 Bus Requested */
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{
/* if z80 was running, resynchronize with 68k */
if (zstate == 1)
z80_run(cycles);
/* request Z80 bus */
zstate |= 2;
/* enable 68k access */
if (zstate & 1)
{
m68k_memory_map[0xa0].read8 = z80_read_byte;
m68k_memory_map[0xa0].read16 = z80_read_word;
m68k_memory_map[0xa0].write8 = z80_write_byte;
m68k_memory_map[0xa0].write16 = z80_write_word;
}
}
else /* Z80 Bus Released */
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{
/* if z80 is restarted, resynchronize with 68k */
if (zstate == 3)
mcycles_z80 = cycles;
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/* release Z80 bus */
zstate &= 1;
/* disable 68k access */
m68k_memory_map[0xa0].read8 = m68k_read_bus_8;
m68k_memory_map[0xa0].read16 = m68k_read_bus_16;
m68k_memory_map[0xa0].write8 = m68k_unused_8_w;
m68k_memory_map[0xa0].write16 = m68k_unused_16_w;
}
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}
void gen_zreset_w(unsigned int state, unsigned int cycles)
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{
/* detect !ZRESET transitions */
if (state == (zstate & 1))
return;
if (state) /* !ZRESET inactive */
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{
/* if z80 is restarted, resynchronize with 68k */
if (zstate == 0)
mcycles_z80 = cycles;
/* reset Z80 */
z80_reset();
/* negate Z80 reset */
zstate |= 1;
/* enable 68k access */
if (zstate & 1)
{
m68k_memory_map[0xa0].read8 = z80_read_byte;
m68k_memory_map[0xa0].read16 = z80_read_word;
m68k_memory_map[0xa0].write8 = z80_write_byte;
m68k_memory_map[0xa0].write16 = z80_write_word;
}
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}
else /* !ZRESET active */
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{
/* if z80 was running, resynchronize with 68k */
if (zstate == 1)
z80_run(cycles);
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/* assert Z80 reset */
zstate &= 2;
/* disable 68k access */
m68k_memory_map[0xa0].read8 = m68k_read_bus_8;
m68k_memory_map[0xa0].read16 = m68k_read_bus_16;
m68k_memory_map[0xa0].write8 = m68k_unused_8_w;
m68k_memory_map[0xa0].write16 = m68k_unused_16_w;
}
/* reset YM2612 */
fm_reset(cycles);
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}
void gen_zbank_w (unsigned int state)
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{
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zbank = ((zbank >> 1) | ((state & 1) << 23)) & 0xFF8000;
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}
int z80_irq_callback (int param)
{
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return 0xFF;
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}