// license:BSD-3-Clause // copyright-holders:Nigel Barnes /*************************************************************************** Mega Games Cartridge The Mega Games Cartridge (MGC) is a Cartridge for the Acorn Electron, with an Acorn/P.R.E.S. Plus 1 or a Slogger RomBox Plus fitted. It contains a 32 Megabit (4M x 8-Bit) FlashRAM, plus control circuitry, to give 256 x 16K pages of Memory. These 16K blocks can be viewed in various formats. The MGC has been designed to hold and access, via the built-in Menu, up-to 254 Games (the Index and Menu ROM take up the other two 16K blocks). ***************************************************************************/ #include "emu.h" #include "mgc.h" //************************************************************************** // DEVICE DEFINITIONS //************************************************************************** DEFINE_DEVICE_TYPE(ELECTRON_MGC, electron_mgc_device, "electron_mgc", "Electron Mega Games Cartridge") //************************************************************************** // LIVE DEVICE //************************************************************************** //------------------------------------------------- // electron_mgc_device - constructor //------------------------------------------------- electron_mgc_device::electron_mgc_device(const machine_config &mconfig, const char *tag, device_t *owner, const XTAL &clock) : device_t(mconfig, ELECTRON_MGC, tag, owner, clock) , device_electron_cart_interface(mconfig, *this) , m_page_latch(0) , m_control_latch(0) { } //------------------------------------------------- // device_start - device-specific startup //------------------------------------------------- void electron_mgc_device::device_start() { save_item(NAME(m_page_latch)); save_item(NAME(m_control_latch)); } //------------------------------------------------- // device_reset - device-specific reset //------------------------------------------------- void electron_mgc_device::device_reset() { m_page_latch = 0; m_control_latch = 0; } //------------------------------------------------- // read - cartridge data read //------------------------------------------------- uint8_t electron_mgc_device::read(offs_t offset, int infc, int infd, int romqa, int oe, int oe2) { uint8_t data = 0xff; if (oe) { int m_page_mode = BIT(m_control_latch, 2) ? BIT(m_control_latch, 1) : !romqa; data = m_nvram[(offset & 0x3fff) | (m_page_latch << 14) | (m_page_mode << 21)]; } return data; } //------------------------------------------------- // write - cartridge data write //------------------------------------------------- void electron_mgc_device::write(offs_t offset, uint8_t data, int infc, int infd, int romqa, int oe, int oe2) { if (infc) { switch (offset) { case 0x00: m_page_latch = data & 0x7f; break; case 0x08: m_control_latch = data & 0x07; break; } } else if (oe) { int m_page_mode = BIT(m_control_latch, 2) ? BIT(m_control_latch, 1) : !romqa; m_nvram[(offset & 0x3fff) | (m_page_latch << 14) | (m_page_mode << 21)] = data; } }