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// license:BSD-3-Clause
// copyright-holders:Wilbert Pol
#include "emu.h"
#include "nomapper.h"
DEFINE_DEVICE_TYPE(MSX_CART_NOMAPPER, msx_cart_nomapper_device, "msx_cart_nomapper", "MSX Cartridge - ROM")
msx_cart_nomapper_device::msx_cart_nomapper_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
: device_t(mconfig, MSX_CART_NOMAPPER, tag, owner, clock)
, msx_cart_interface(mconfig, *this)
, m_start_address(0)
, m_end_address(0)
{
}
void msx_cart_nomapper_device::device_start()
{
}
void msx_cart_nomapper_device::initialize_cartridge()
{
uint32_t size = get_rom_size();
uint8_t *rom = get_rom_base();
// determine start address
// default to $4000
m_start_address = 0x4000;
switch (size)
{
/* 8KB/16KB */
case 0x2000: case 0x4000:
{
uint16_t start = rom[3] << 8 | rom[2];
// start address of $0000: call address in the $4000 region: $4000, else $8000
if (start == 0)
{
if ((rom[5] & 0xc0) == 0x40)
m_start_address = 0x4000;
else
m_start_address = 0x8000;
}
// start address in the $8000 region: $8000, else default
else if ((start & 0xc000) == 0x8000)
m_start_address = 0x8000;
break;
}
/* 32KB */
case 0x8000:
// take default, check when no "AB" at $0000, but "AB" at $4000
if (rom[0] != 'A' && rom[1] != 'B' && rom[0x4000] == 'A' && rom[0x4001] == 'B')
{
uint16_t start = rom[0x4003] << 8 | rom[0x4002];
// start address of $0000 and call address in the $4000 region, or start address outside the $8000 region: $0000, else default
if ((start == 0 && (rom[0x4005] & 0xc0) == 0x40) || start < 0x8000 || start >= 0xc000)
m_start_address = 0;
}
break;
/* 48KB */
case 0xc000:
// "AB" at $0000, but no "AB" at $4000, not "AB": $0000
if (rom[0] == 'A' && rom[1] == 'B' && rom[0x4000] != 'A' && rom[0x4001] != 'B')
m_start_address = 0x4000;
else
m_start_address = 0;
break;
/* 64KB */
default:
m_start_address = 0;
break;
}
m_end_address = std::min<uint32_t>(m_start_address + size, 0x10000);
}
uint8_t msx_cart_nomapper_device::read_cart(offs_t offset)
{
if ( offset >= m_start_address && offset < m_end_address )
{
return get_rom_base()[offset - m_start_address];
}
return 0xff;
}
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