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Diffstat (limited to 'src/devices/bus/coleco/cartridge/megacart.cpp')
-rw-r--r--src/devices/bus/coleco/cartridge/megacart.cpp93
1 files changed, 93 insertions, 0 deletions
diff --git a/src/devices/bus/coleco/cartridge/megacart.cpp b/src/devices/bus/coleco/cartridge/megacart.cpp
new file mode 100644
index 00000000000..dddf28ec851
--- /dev/null
+++ b/src/devices/bus/coleco/cartridge/megacart.cpp
@@ -0,0 +1,93 @@
+// 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, uint32_t 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()
+{
+}
+
+
+//-------------------------------------------------
+// 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;
+}