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// license:BSD-3-Clause
// copyright-holders:Mark/Space Inc.
/**********************************************************************
ColecoVision MegaCart emulation
**********************************************************************/
#include "emu.h"
#include "megacart.h"
//**************************************************************************
// DEVICE DEFINITIONS
//**************************************************************************
DEFINE_DEVICE_TYPE(COLECOVISION_MEGACART, colecovision_megacart_cartridge_device, "colecovision_megacart", "ColecoVision MegaCart")
//**************************************************************************
// LIVE DEVICE
//**************************************************************************
//-------------------------------------------------
// colecovision_megacart_cartridge_device - constructor
//-------------------------------------------------
colecovision_megacart_cartridge_device::colecovision_megacart_cartridge_device(const machine_config &mconfig, const char *tag, device_t *owner, const XTAL &clock) :
device_t(mconfig, COLECOVISION_MEGACART, tag, owner, clock),
device_colecovision_cartridge_interface(mconfig, *this),
m_bankcount(0),
m_activebank(0)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void colecovision_megacart_cartridge_device::device_start()
{
save_item(NAME(m_bankcount));
save_item(NAME(m_activebank));
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void colecovision_megacart_cartridge_device::device_reset()
{
m_bankcount = m_rom_size >> 14;
m_activebank = 0;
}
//-------------------------------------------------
// read - cartridge data read
//-------------------------------------------------
uint8_t colecovision_megacart_cartridge_device::bd_r(offs_t offset, uint8_t data, int _8000, int _a000, int _c000, int _e000)
{
if (!_8000 || !_a000 || !_c000 || !_e000)
{
if (m_bankcount > 2)
{
// offset as passed to us is a delta from address 0x8000.
if (offset >= 0x7FC0)
{
// Reads within the final 64 bytes select which megacart bank is active.
m_activebank = offset & (m_bankcount - 1);
}
if (offset >= 0x4000)
{
// The offset is within the active megacart bank.
offset = (m_activebank << 14) + (offset - 0x4000);
}
else
{
// The offset is within the last bank.
offset = (m_bankcount << 14) + (offset - 0x4000);
}
}
data = m_rom[offset];
}
return data;
}
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