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// license:BSD-3-Clause
// copyright-holders:AJR
/***************************************************************************
Mark 1 FORTH Computer microcode disassembler
***************************************************************************/
#include "emu.h"
#include "mk1dasm.h"
mk1_disassembler::mk1_disassembler()
: util::disasm_interface()
{
}
u32 mk1_disassembler::opcode_alignment() const
{
return 1;
}
namespace {
std::string_view s_srcs[8] = { "w", "ip", "tos", "rs", "[w]", "[ip]", "0", "f" };
std::string_view s_dsts[8] = { "w", "ip", "tos", "rs", "[w]", "op", "a", "b" };
// "b??" is the actual mnemonic Andrew Holme's assembler uses (condition is sign or less depending on operation)
std::string_view s_skips[4] = { "b??", "bcs", "bne", "bis" };
} // anonymous namespace
offs_t mk1_disassembler::disassemble(std::ostream &stream, offs_t pc, const mk1_disassembler::data_buffer &opcodes, const mk1_disassembler::data_buffer ¶ms)
{
const u8 uop = opcodes.r8(pc);
if (uop < 0x80)
{
// Move LSB/MSB
util::stream_format(stream, "mov %s%s, %s%s",
s_dsts[BIT(uop, 0, 3)],
BIT(uop, 2) ? "" : (BIT(uop, 6) ? ".h" : ".l"),
s_srcs[BIT(uop, 3, 3)],
BIT(uop, 5) ? "" : (BIT(uop, 6) ? ".h" : ".l"));
return 1 | SUPPORTED;
}
else if (uop >= 0xc0)
{
// Conditional skip
const u8 disp = BIT(uop, 0, 4);
util::stream_format(stream, "%s %d ; $%03x", s_skips[BIT(uop, 4, 2)], disp, (pc + 1 + disp) & 0xfff);
return 1 | STEP_COND | SUPPORTED;
}
else if (uop >= 0xb0)
{
// Jump indirect
stream << "xop";
return 1 | SUPPORTED;
}
else if (uop >= 0xa0)
{
// Set ALU function
stream << "alu ";
switch (BIT(uop, 0, 4))
{
case 0:
stream << "add";
break;
case 1:
stream << "adc";
break;
case 2:
stream << "sub";
break;
case 3:
stream << "sbb";
break;
case 4:
stream << "asl";
break;
case 5:
stream << "rol";
break;
case 8:
stream << "a"; // was also to have been "0="
break;
case 9:
stream << "b";
break;
case 10:
stream << "and";
break;
case 11:
stream << "or";
break;
case 12:
stream << "not";
break;
case 13:
stream << "xor";
break;
case 14:
stream << "a=b";
break;
default:
util::stream_format(stream, "%d", BIT(uop, 0, 4));
break;
}
return 1 | SUPPORTED;
}
else if (uop >= 0x90)
{
// Jump direct
util::stream_format(stream, "jmp %d", BIT(uop, 0, 4));
return 1 | STEP_OUT | SUPPORTED;
}
else if (BIT(uop, 2))
{
// Disable/enable IRQ
if (BIT(uop, 3))
stream << "eni";
else
stream << "dis";
return 1 | SUPPORTED;
}
else
{
// Increment/decrement
if (BIT(uop, 3))
stream << "inc ";
else
stream << "dec ";
if (BIT(uop, 1))
util::stream_format(stream, "%csp", BIT(uop, 0) ? 'r' : 'p');
else
stream << s_dsts[BIT(uop, 0)];
return 1 | SUPPORTED;
}
}
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