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path: root/src/emu/bus/msx_slot/bunsetsu.c
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/*
  Emulation for the bunsetsu internal firmware mapper found in a number of MSX machines
*/

#include "emu.h"
#include "bunsetsu.h"


const device_type MSX_SLOT_BUNSETSU = &device_creator<msx_slot_bunsetsu_device>;


msx_slot_bunsetsu_device::msx_slot_bunsetsu_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
	: msx_slot_rom_device(mconfig, MSX_SLOT_BUNSETSU, "MSX Internal BUNSETSU", tag, owner, clock, "msx_slot_bunsetsu", __FILE__)
	, m_bunsetsu_region(NULL)
	, m_bunsetsu_region_tag(NULL)
	, m_bunsetsu_address(0)
{
}


void msx_slot_bunsetsu_device::device_start()
{
	msx_slot_rom_device::device_start();

	if (m_bunsetsu_region_tag == NULL)
	{
		fatalerror("msx_slot_bunsetsu_device: no bunsetsu region tag specified\n");
	}

	m_bunsetsu_region = owner()->memregion(m_bunsetsu_region_tag);

	if (m_bunsetsu_region == NULL)
	{
		fatalerror("msx_slot_bunsetsu_device: Unable to find region with tag '%s'\n", m_bunsetsu_region_tag);
	}

	if (m_bunsetsu_region->bytes() != 0x20000)
	{
		fatalerror("msx_slot_bunsetsu_device: Bunsetsu region must be 0x20000 bytes.\n");
	}
}


void msx_slot_bunsetsu_device::device_reset()
{
	m_bunsetsu_address = 0;
}


READ8_MEMBER(msx_slot_bunsetsu_device::read)
{
	if (offset == 0xbfff)
	{
		return m_bunsetsu_region->u8(m_bunsetsu_address++ & 0x1ffff);
	}
	return msx_slot_rom_device::read(space, offset);
}


WRITE8_MEMBER(msx_slot_bunsetsu_device::write)
{
	switch (offset)
	{
		case 0xbffc:
			m_bunsetsu_address = (m_bunsetsu_address & 0xffff00) | data;
			break;

		case 0xbffd:
			m_bunsetsu_address = (m_bunsetsu_address & 0xff00ff) | (data << 8);
			break;

		case 0xbffe:
			m_bunsetsu_address = (m_bunsetsu_address & 0x00ffff) | (data << 16);
			break;
	}
}