diff options
Diffstat (limited to 'src/devices/bus/bbc/cart/mega256.cpp')
-rw-r--r-- | src/devices/bus/bbc/cart/mega256.cpp | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/src/devices/bus/bbc/cart/mega256.cpp b/src/devices/bus/bbc/cart/mega256.cpp new file mode 100644 index 00000000000..f0348df2e74 --- /dev/null +++ b/src/devices/bus/bbc/cart/mega256.cpp @@ -0,0 +1,97 @@ +// license:BSD-3-Clause +// copyright-holders:Nigel Barnes +/*************************************************************************** + + Solidisk Mega 256 cartridge emulation + + http://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Solidisk_Mega256.html + +***************************************************************************/ + +#include "emu.h" +#include "mega256.h" + + +//************************************************************************** +// DEVICE DEFINITIONS +//************************************************************************** + +DEFINE_DEVICE_TYPE(BBC_MEGA256, bbc_mega256_device, "bbc_mega256", "Solidisk Mega 256 cartridge") + + +//************************************************************************** +// LIVE DEVICE +//************************************************************************** + +//------------------------------------------------- +// bbc_mega256_device - constructor +//------------------------------------------------- + +bbc_mega256_device::bbc_mega256_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) + : device_t(mconfig, BBC_MEGA256, tag, owner, clock) + , device_bbc_cart_interface(mconfig, *this) + , m_page(0) +{ +} + +//------------------------------------------------- +// device_start - device-specific startup +//------------------------------------------------- + +void bbc_mega256_device::device_start() +{ + // register for save states + save_item(NAME(m_page)); +} + +//------------------------------------------------- +// device_reset - device-specific reset +//------------------------------------------------- + +void bbc_mega256_device::device_reset() +{ + m_page = 0x00; +} + +//------------------------------------------------- +// read - cartridge data read +//------------------------------------------------- + +uint8_t bbc_mega256_device::read(offs_t offset, int infc, int infd, int romqa, int oe, int oe2) +{ + uint8_t data = 0xff; + + if (oe) + { + if (romqa) + { + data = m_rom[offset & 0x1fff]; + } + else + { + data = m_ram[(offset & 0x3fff) | (m_page << 14)]; + } + } + + return data; +} + +//------------------------------------------------- +// write - cartridge data write +//------------------------------------------------- + +void bbc_mega256_device::write(offs_t offset, uint8_t data, int infc, int infd, int romqa, int oe, int oe2) +{ + if (oe) + { + if (romqa) + { + // Not known whether this latch is fully decoded. + if (offset == 0x3fff) m_page = data & 0x0f; + } + else + { + m_ram[(offset & 0x3fff) | (m_page << 14)] = data; + } + } +} |