mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
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310 lines
7.7 KiB
C
310 lines
7.7 KiB
C
![]() |
/***************************************************************************************
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* Genesis Plus
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* Z80 bus controller (MD & MS compatibility modes)
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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 (2007-2011), 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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/*--------------------------------------------------------------------------*/
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/* Handlers for access to unused addresses and those which make the */
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/* machine lock up. */
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/*--------------------------------------------------------------------------*/
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static inline void z80_unused_w(unsigned int address, unsigned char data)
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{
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#ifdef LOGERROR
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error("Z80 unused write %04X = %02X (%x)\n", address, data, Z80.pc.w.l);
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#endif
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}
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static inline unsigned char z80_unused_r(unsigned int address)
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{
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#ifdef LOGERROR
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error("Z80 unused read %04X (%x)\n", address, Z80.pc.w.l);
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#endif
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return 0xFF;
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}
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static inline void z80_lockup_w(unsigned int address, unsigned char data)
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{
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#ifdef LOGERROR
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error("Z80 lockup write %04X = %02X (%x)\n", address, data, Z80.pc.w.l);
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#endif
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if (!config.force_dtack)
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{
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mcycles_z80 = 0xFFFFFFFF;
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zstate = 0;
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}
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}
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static inline unsigned char z80_lockup_r(unsigned int address)
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{
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#ifdef LOGERROR
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error("Z80 lockup read %04X (%x)\n", address, Z80.pc.w.l);
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#endif
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if (!config.force_dtack)
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{
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mcycles_z80 = 0xFFFFFFFF;
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zstate = 0;
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}
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return 0xFF;
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}
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/*--------------------------------------------------------------------------*/
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/* Z80 Memory handlers (Genesis mode) */
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/*--------------------------------------------------------------------------*/
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unsigned char z80_md_memory_r(unsigned int address)
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{
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switch((address >> 13) & 7)
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{
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case 0: /* $0000-$3FFF: Z80 RAM (8K mirrored) */
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case 1:
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{
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return zram[address & 0x1FFF];
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}
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case 2: /* $4000-$5FFF: YM2612 */
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{
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return fm_read(mcycles_z80, address & 3);
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}
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case 3: /* $7F00-$7FFF: VDP */
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{
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if ((address >> 8) == 0x7F)
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{
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return (*zbank_memory_map[0xc0].read)(address);
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}
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return z80_unused_r(address);
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}
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default: /* $8000-$FFFF: 68k bank (32K) */
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{
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address = zbank | (address & 0x7FFF);
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unsigned int slot = address >> 16;
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if (zbank_memory_map[slot].read)
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{
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return (*zbank_memory_map[slot].read)(address);
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}
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return READ_BYTE(m68k_memory_map[slot].base, address & 0xFFFF);
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}
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}
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}
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void z80_md_memory_w(unsigned int address, unsigned char data)
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{
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switch((address >> 13) & 7)
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{
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case 0: /* $0000-$3FFF: Z80 RAM (8K mirrored) */
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case 1:
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{
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zram[address & 0x1FFF] = data;
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return;
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}
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case 2: /* $4000-$5FFF: YM2612 */
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{
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fm_write(mcycles_z80, address & 3, data);
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return;
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}
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case 3: /* Bank register and VDP */
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{
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switch(address >> 8)
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{
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case 0x60: /* $6000-$60FF: Bank register */
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{
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gen_zbank_w(data & 1);
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return;
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}
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case 0x7F: /* $7F00-$7FFF: VDP */
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{
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(*zbank_memory_map[0xc0].write)(address, data);
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return;
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}
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default:
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{
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z80_unused_w(address, data);
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return;
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}
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}
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}
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default: /* $8000-$FFFF: 68k bank (32K) */
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{
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address = zbank | (address & 0x7FFF);
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unsigned int slot = address >> 16;
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if (zbank_memory_map[slot].write)
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{
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(*zbank_memory_map[slot].write)(address, data);
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return;
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}
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WRITE_BYTE(m68k_memory_map[slot].base, address & 0xFFFF, data);
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return;
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}
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}
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}
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/*--------------------------------------------------------------------------*/
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/* Z80 Memory handlers (Master System mode) */
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/*--------------------------------------------------------------------------*/
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unsigned char z80_sms_memory_r(unsigned int address)
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{
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return z80_readmap[(address) >> 10][(address) & 0x03FF];
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}
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/*--------------------------------------------------------------------------*/
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/* Z80 Port handlers */
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/*--------------------------------------------------------------------------*/
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/*
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Ports are unused when not in Mark III compatibility mode.
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Genesis games that access ports anyway:
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Thunder Force IV reads port $BF in it's interrupt handler.
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*/
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unsigned char z80_unused_port_r(unsigned int port)
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{
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#if LOGERROR
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error("Z80 unused read from port %04X (%x)\n", port, Z80.pc.w.l);
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#endif
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return 0xFF;
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}
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void z80_unused_port_w(unsigned int port, unsigned char data)
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{
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#if LOGERROR
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error("Z80 unused write to port %04X = %02X (%x)\n", port, data, Z80.pc.w.l);
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#endif
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}
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void z80_sms_port_w(unsigned int port, unsigned char data)
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{
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switch (port & 0xC1)
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{
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case 0x01:
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{
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io_z80_write(data);
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return;
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}
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case 0x40:
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case 0x41:
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{
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psg_write(mcycles_z80, data);
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return;
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}
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case 0x80:
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{
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vdp_z80_data_w(data);
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return;
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}
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case 0x81:
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{
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vdp_z80_ctrl_w(data);
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return;
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}
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default:
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{
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if ((port & 0xFF) == 0x3E)
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{
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/* Memory Control Register */
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/* NB: this register does not exist on MD hardware but is partially emulated to support BIOS ROM image files */
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if (data & 0x40)
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{
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/* Assume only BIOS would disable Cartridge ROM */
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if (data & 0x08)
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{
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/* BIOS ROM disabled */
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sms_cart_switch(0);
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}
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else
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{
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/* BIOS ROM enabled */
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sms_cart_switch(1);
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}
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}
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return;
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}
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if ((port >= 0xF0) && (config.ym2413_enabled))
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{
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fm_write(mcycles_z80, port&3, data);
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return;
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}
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z80_unused_port_w(port, data);
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return;
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}
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}
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}
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unsigned char z80_sms_port_r(unsigned int port)
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{
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switch (port & 0xC1)
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{
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case 0x40:
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{
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return ((vdp_hvc_r(mcycles_z80) >> 8) & 0xFF);
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}
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case 0x41:
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{
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return (vdp_hvc_r(mcycles_z80) & 0xFF);
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}
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case 0x80:
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{
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return vdp_z80_data_r();
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}
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case 0x81:
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{
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return (vdp_ctrl_r(mcycles_z80) & 0xFF);
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}
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default:
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{
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port &= 0xFF;
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if ((port == 0xC0) || (port == 0xC1) || (port == 0xDC) || (port == 0xDD) || (port == 0xDE) || (port == 0xDF))
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{
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return io_z80_read(port & 1);
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}
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if ((port >= 0xF0) && (config.ym2413_enabled))
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{
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return YM2413Read(port & 3);
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}
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return z80_unused_port_r(port);
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}
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}
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}
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