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https://github.com/holub/mame
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77cf3b0413
* Support Colecovision Megacart. Assume that a rom file that is more than 32K in size is a megacart and that it should be bankswitched using Megacart protocol. * Put megacart functionality in its own cartridge type.
94 lines
2.5 KiB
C++
94 lines
2.5 KiB
C++
// license:BSD-3-Clause
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// copyright-holders:Mark/Space Inc.
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/**********************************************************************
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ColecoVision MegaCart emulation
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**********************************************************************/
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#include "emu.h"
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#include "megacart.h"
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//**************************************************************************
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// DEVICE DEFINITIONS
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//**************************************************************************
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DEFINE_DEVICE_TYPE(COLECOVISION_MEGACART, colecovision_megacart_cartridge_device, "colecovision_megacart", "ColecoVision MegaCart")
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//**************************************************************************
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// LIVE DEVICE
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//**************************************************************************
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//-------------------------------------------------
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// colecovision_megacart_cartridge_device - constructor
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//-------------------------------------------------
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colecovision_megacart_cartridge_device::colecovision_megacart_cartridge_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
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device_t(mconfig, COLECOVISION_MEGACART, tag, owner, clock),
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device_colecovision_cartridge_interface(mconfig, *this),
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m_bankcount(0),
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m_activebank(0)
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{
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}
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//-------------------------------------------------
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// device_start - device-specific startup
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//-------------------------------------------------
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void colecovision_megacart_cartridge_device::device_start()
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{
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}
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//-------------------------------------------------
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// device_reset - device-specific reset
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//-------------------------------------------------
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void colecovision_megacart_cartridge_device::device_reset()
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{
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m_bankcount = m_rom_size >> 14;
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m_activebank = 0;
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}
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//-------------------------------------------------
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// read - cartridge data read
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//-------------------------------------------------
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uint8_t colecovision_megacart_cartridge_device::bd_r(offs_t offset, uint8_t data, int _8000, int _a000, int _c000, int _e000)
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{
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if (!_8000 || !_a000 || !_c000 || !_e000)
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{
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if (m_bankcount > 2)
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{
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// offset as passed to us is a delta from address 0x8000.
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if (offset >= 0x7FC0)
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{
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// Reads within the final 64 bytes select which megacart bank is active.
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m_activebank = offset & (m_bankcount - 1);
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}
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if (offset >= 0x4000)
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{
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// The offset is within the active megacart bank.
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offset = (m_activebank << 14) + (offset - 0x4000);
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}
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else
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{
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// The offset is within the last bank.
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offset = (m_bankcount << 14) + (offset - 0x4000);
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}
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}
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data = m_rom[offset];
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}
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return data;
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}
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