mirror of
https://github.com/holub/mame
synced 2025-05-22 21:58:57 +03:00
1e09ab0ceb
* create derived 6502 type for XaviX because it has at least one custom 4-byte opcode that doesn't fit any other type. treating that opcode as NOP for now. have a feeling it might be something to do with the other integrated hardware, might be 'execute co-processor code chain at this address' or something similar It isn't a standard JSL (Jump Subroutine Long) like the SNES cpu opcode in the same place as this, it seems to point at some code-like structures tho) could also be a secondary operation mode with different encoding like ARM's Thumb mode tho I guess. We currently only have a single XaviX based dump (taitons1) but there are more on the way. I'm going to see if the code flow makes any sense at all with these missing, or if any of it gives a clue as to what they should actually do. * xavix - let's call these callf and retf then after further investigation these are some kind of extra 'long jump' subroutine / task handlers, the 0x80 also being a custom opcode was throwing me off trying to identify them before. looks like they might have been hacking 65816 features into the regular 6502 core? * prepare for extra address bits (nw) * better program flow (nw)
126 lines
2.6 KiB
C++
126 lines
2.6 KiB
C++
// license:BSD-3-Clause
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// copyright-holders:David Haywood
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/***************************************************************************
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xavix.c
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6502 with custom opcodes
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integrated gfx / sound / coprocessor?
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***************************************************************************/
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#include "emu.h"
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#include "xavix.h"
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#include "xavixd.h"
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DEFINE_DEVICE_TYPE(XAVIX, xavix_device, "xavix", "XaviX")
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xavix_device::xavix_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
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m6502_device(mconfig, XAVIX, tag, owner, clock),
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XPC(0)
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{
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program_config.m_addr_width = 24;
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program_config.m_logaddr_width = 24;
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sprogram_config.m_addr_width = 24;
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sprogram_config.m_logaddr_width = 24;
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}
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util::disasm_interface *xavix_device::create_disassembler()
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{
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return new xavix_disassembler;
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}
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void xavix_device::device_start()
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{
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if(direct_disabled)
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mintf = std::make_unique<mi_xavix_nd>(this);
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else
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mintf = std::make_unique<mi_xavix_normal>(this);
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init();
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state_add(STATE_GENPC, "GENPC", XPC).callexport().noshow();
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state_add(STATE_GENPCBASE, "CURPC", XPC).callexport().noshow();
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}
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void xavix_device::state_export(const device_state_entry &entry)
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{
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switch(entry.index()) {
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case STATE_GENPC:
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case STATE_GENPCBASE:
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XPC = adr_with_bank(NPC);
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break;
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}
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}
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void xavix_device::device_reset()
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{
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m_farbank = 0;
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XPC = 0;
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m6502_device::device_reset();
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}
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xavix_device::mi_xavix_normal::mi_xavix_normal(xavix_device *_base)
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{
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base = _base;
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}
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uint8_t xavix_device::mi_xavix_normal::read(uint16_t adr)
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{
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if (adr < 0x8000)
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return program->read_byte(adr);
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else
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return program->read_byte(base->adr_with_bank(adr));
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}
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uint8_t xavix_device::mi_xavix_normal::read_sync(uint16_t adr)
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{
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if (adr < 0x8000)
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return sdirect->read_byte(adr);
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else
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return sdirect->read_byte(base->adr_with_bank(adr));
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}
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uint8_t xavix_device::mi_xavix_normal::read_arg(uint16_t adr)
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{
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if (adr < 0x8000)
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return direct->read_byte(adr);
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else
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return direct->read_byte(base->adr_with_bank(adr));
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}
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void xavix_device::mi_xavix_normal::write(uint16_t adr, uint8_t val)
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{
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if (adr < 0x8000)
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program->write_byte(adr, val);
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else
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program->write_byte(base->adr_with_bank(adr), val);
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}
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xavix_device::mi_xavix_nd::mi_xavix_nd(xavix_device *_base) : mi_xavix_normal(_base)
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{
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}
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uint8_t xavix_device::mi_xavix_nd::read_sync(uint16_t adr)
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{
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if (adr < 0x8000)
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return sprogram->read_byte(adr);
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else
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return sprogram->read_byte(base->adr_with_bank(adr));
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}
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uint8_t xavix_device::mi_xavix_nd::read_arg(uint16_t adr)
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{
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if (adr < 0x8000)
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return program->read_byte(adr);
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else
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return program->read_byte(base->adr_with_bank(adr));
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}
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#include "cpu/m6502/xavix.hxx"
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