summaryrefslogtreecommitdiffstatshomepage
path: root/src/mame/nintendo/m6502_swap_op_d5_d6.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'src/mame/nintendo/m6502_swap_op_d5_d6.cpp')
-rw-r--r--src/mame/nintendo/m6502_swap_op_d5_d6.cpp142
1 files changed, 142 insertions, 0 deletions
diff --git a/src/mame/nintendo/m6502_swap_op_d5_d6.cpp b/src/mame/nintendo/m6502_swap_op_d5_d6.cpp
new file mode 100644
index 00000000000..90616b79396
--- /dev/null
+++ b/src/mame/nintendo/m6502_swap_op_d5_d6.cpp
@@ -0,0 +1,142 @@
+// license:BSD-3-Clause
+// copyright-holders:David Shah, David Haywood
+/***************************************************************************
+
+ m6502_swap_op_d5_d6.cpp
+
+ 6502 / RP2A03 with instruction scrambling
+
+ Seen on die marked VH2009, used on polmega, silv35
+ these are RP2A03 derived CPUs used on VTxx systems
+
+ VT1682 systems with this scrambling currently derive from M6502 type
+ but this might be incorrect
+
+***************************************************************************/
+
+#include "emu.h"
+#include "m6502_swap_op_d5_d6.h"
+
+DEFINE_DEVICE_TYPE(M6502_SWAP_OP_D5_D6, m6502_swap_op_d5_d6, "m6502_swap_op_d5_d6", "M6502 swapped D5/D6")
+DEFINE_DEVICE_TYPE(RP2A03_CORE_SWAP_OP_D5_D6, rp2a03_core_swap_op_d5_d6, "rp2a03_core_swap_op_d5_d6", "RP2A03 core with swapped D5/D6")
+
+m6502_swap_op_d5_d6::m6502_swap_op_d5_d6(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
+ m6502_device(mconfig, M6502_SWAP_OP_D5_D6, tag, owner, clock)
+{
+}
+
+void m6502_swap_op_d5_d6::device_start()
+{
+ mintf = std::make_unique<mi_decrypt>();
+ init();
+}
+
+void m6502_swap_op_d5_d6::device_reset()
+{
+ downcast<mi_decrypt &>(*mintf).m_encryption_enabled = true;
+ m6502_device::device_reset();
+}
+
+void m6502_swap_op_d5_d6::set_encryption_state(bool state)
+{
+ downcast<mi_decrypt &>(*mintf).m_encryption_enabled = state;
+}
+
+uint8_t m6502_swap_op_d5_d6::mi_decrypt::descramble(uint8_t op)
+{
+ if (m_encryption_enabled)
+ return bitswap<8>(op, 7, 5, 6, 4, 3, 2, 1, 0);
+ else
+ return op;
+}
+
+uint8_t m6502_swap_op_d5_d6::mi_decrypt::read_sync(uint16_t adr)
+{
+ uint8_t res = cprogram.read_byte(adr);
+
+ res = descramble(res);
+
+ return res;
+}
+
+std::unique_ptr<util::disasm_interface> m6502_swap_op_d5_d6::create_disassembler()
+{
+ return std::make_unique<disassembler>(downcast<mi_decrypt *>(mintf.get()));
+}
+
+m6502_swap_op_d5_d6::disassembler::disassembler(mi_decrypt *mi) : mintf(mi)
+{
+}
+
+u32 m6502_swap_op_d5_d6::disassembler::interface_flags() const
+{
+ return SPLIT_DECRYPTION;
+}
+
+u8 m6502_swap_op_d5_d6::disassembler::decrypt8(u8 value, offs_t pc, bool opcode) const
+{
+ return opcode ? mintf->descramble(value) : value;
+}
+
+
+
+
+
+rp2a03_core_swap_op_d5_d6::rp2a03_core_swap_op_d5_d6(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
+ rp2a03_core_device(mconfig, RP2A03_CORE_SWAP_OP_D5_D6, tag, owner, clock)
+{
+}
+
+void rp2a03_core_swap_op_d5_d6::device_start()
+{
+ mintf = std::make_unique<mi_decrypt>();
+ init();
+}
+
+void rp2a03_core_swap_op_d5_d6::device_reset()
+{
+ downcast<mi_decrypt &>(*mintf).m_encryption_enabled = true;
+ rp2a03_core_device::device_reset();
+}
+
+void rp2a03_core_swap_op_d5_d6::set_encryption_state(bool state)
+{
+ downcast<mi_decrypt &>(*mintf).m_encryption_enabled = state;
+}
+
+uint8_t rp2a03_core_swap_op_d5_d6::mi_decrypt::descramble(uint8_t op)
+{
+ if (m_encryption_enabled)
+ return bitswap<8>(op, 7, 5, 6, 4, 3, 2, 1, 0);
+ else
+ return op;
+}
+
+uint8_t rp2a03_core_swap_op_d5_d6::mi_decrypt::read_sync(uint16_t adr)
+{
+ uint8_t res = cprogram.read_byte(adr);
+
+ res = descramble(res);
+
+ return res;
+}
+
+std::unique_ptr<util::disasm_interface> rp2a03_core_swap_op_d5_d6::create_disassembler()
+{
+ return std::make_unique<disassembler>(downcast<mi_decrypt *>(mintf.get()));
+}
+
+rp2a03_core_swap_op_d5_d6::disassembler::disassembler(mi_decrypt *mi) : mintf(mi)
+{
+}
+
+u32 rp2a03_core_swap_op_d5_d6::disassembler::interface_flags() const
+{
+ return SPLIT_DECRYPTION;
+}
+
+u8 rp2a03_core_swap_op_d5_d6::disassembler::decrypt8(u8 value, offs_t pc, bool opcode) const
+{
+ return opcode ? mintf->descramble(value) : value;
+}
+