// license:BSD-3-Clause // copyright-holders:Fabio Priuli /*********************************************************************************************************** Game Genie pass-thorugh cart emulation based on Charles MacDonald's docs: http://cgfm2.emuviews.com/txt/genie.txt There is an interesting difference between Rev.0 and Rev.A After the codes has been entered, the former just performs a last write to the MODE register (m_gg_regs[0]) which both sets the enable bits for the 6 available cheats (in the low 8 bits) and locks the GG so that later reads goes to the piggyback cart. The latter revision, instead, performs the same operations in two subsequent 8bit writes, accessing separately the low and high bits of the register. ***********************************************************************************************************/ #include "emu.h" #include "ggenie.h" #include "rom.h" //------------------------------------------------- // md_rom_device - constructor //------------------------------------------------- DEFINE_DEVICE_TYPE(MD_ROM_GAMEGENIE, md_rom_ggenie_device, "md_ggenie", "MD Game Genie") md_rom_ggenie_device::md_rom_ggenie_device(const machine_config &mconfig, const char *tag, device_t *owner, const XTAL &clock) : device_t(mconfig, MD_ROM_GAMEGENIE, tag, owner, clock) , device_md_cart_interface(mconfig, *this) , m_exp(*this, "subslot") , m_gg_bypass(0), m_reg_enable(0) { } void md_rom_ggenie_device::device_start() { save_item(NAME(m_gg_bypass)); save_item(NAME(m_reg_enable)); save_item(NAME(m_gg_regs)); save_item(NAME(m_gg_addr)); save_item(NAME(m_gg_data)); } void md_rom_ggenie_device::device_reset() { m_gg_bypass = 0; m_reg_enable = 0; memset(m_gg_regs, 0, sizeof(m_gg_regs)); memset(m_gg_addr, 0, sizeof(m_gg_addr)); memset(m_gg_data, 0, sizeof(m_gg_data)); } /*------------------------------------------------- mapper specific handlers -------------------------------------------------*/ uint16_t md_rom_ggenie_device::read(offs_t offset) { if (!m_gg_bypass || !m_exp->m_cart) { if (m_reg_enable) return m_gg_regs[offset & 0x1f]; else return m_rom[MD_ADDR(offset)]; } if (m_exp->m_cart) { if (offset == m_gg_addr[0]/2 && BIT(m_gg_regs[0], 0)) return m_gg_data[0]; else if (offset == m_gg_addr[1]/2 && BIT(m_gg_regs[0], 1)) return m_gg_data[1]; else if (offset == m_gg_addr[2]/2 && BIT(m_gg_regs[0], 2)) return m_gg_data[2]; else if (offset == m_gg_addr[3]/2 && BIT(m_gg_regs[0], 3)) return m_gg_data[3]; else if (offset == m_gg_addr[4]/2 && BIT(m_gg_regs[0], 4)) return m_gg_data[4]; else if (offset == m_gg_addr[5]/2 && BIT(m_gg_regs[0], 5)) return m_gg_data[5]; else return m_exp->m_cart->read(offset); } else return 0xffff; } void md_rom_ggenie_device::write(offs_t offset, uint16_t data, uint16_t mem_mask) { if (offset >= 0x40/2) return; if (ACCESSING_BITS_0_7) m_gg_regs[offset] = (m_gg_regs[offset] & 0xff00) | (data & 0x00ff); if (ACCESSING_BITS_8_15) m_gg_regs[offset] = (m_gg_regs[offset] & 0x00ff) | (data & 0xff00); //printf("write to 0x%X, data 0x%X\n", offset, data); // MODE if (offset == 0) { // bit10 set = read goes to piggyback cart if (data & 0x400) m_gg_bypass = 1; // bit10 unset = read goes to Game Genie ASIC/ROM else { m_gg_bypass = 0; // bit9 set = read goes to ASIC registers if (data & 0x200) m_reg_enable = 1; // bit9 unset = read goes to GG ROM else m_reg_enable = 0; } // LOCK bit if (data & 0x100) { // addresses m_gg_addr[0] = ((m_gg_regs[2] & 0x3f) << 16) | m_gg_regs[3]; m_gg_addr[1] = ((m_gg_regs[5] & 0x3f) << 16) | m_gg_regs[6]; m_gg_addr[2] = ((m_gg_regs[8] & 0x3f) << 16) | m_gg_regs[9]; m_gg_addr[3] = ((m_gg_regs[11] & 0x3f) << 16) | m_gg_regs[12]; m_gg_addr[4] = ((m_gg_regs[14] & 0x3f) << 16) | m_gg_regs[15]; m_gg_addr[5] = ((m_gg_regs[17] & 0x3f) << 16) | m_gg_regs[18]; // data m_gg_data[0] = m_gg_regs[4]; m_gg_data[1] = m_gg_regs[7]; m_gg_data[2] = m_gg_regs[10]; m_gg_data[3] = m_gg_regs[13]; m_gg_data[4] = m_gg_regs[16]; m_gg_data[5] = m_gg_regs[19]; //printf("mode %X\n", data); //for (int i = 0; i < 6; i++) // printf("addr %d = 0x%X - data 0x%X\n", i, m_gg_addr[i], m_gg_data[i]); } } else if (offset == 1) { // RESET m_gg_regs[1] |= 1; } } static void ggenie_sub_cart(device_slot_interface &device) { device.option_add_internal("rom", MD_STD_ROM); device.option_add_internal("rom_svp", MD_STD_ROM); device.option_add_internal("rom_sram", MD_ROM_SRAM); device.option_add_internal("rom_sramsafe", MD_ROM_SRAM); device.option_add_internal("rom_fram", MD_ROM_FRAM); } //------------------------------------------------- // device_add_mconfig - add device configuration //------------------------------------------------- void md_rom_ggenie_device::device_add_mconfig(machine_config &config) { MD_CART_SLOT(config, m_exp, ggenie_sub_cart, nullptr); m_exp->set_must_be_loaded(false); }