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gigatron: Disassembly tweaks (nw)

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- Fix disassembly of control instructions in non-direct addressing modes
- Fix edge case for jump page calculation (at PC = $xxFF)
- Use NOP shorthand for LD AC
- Acknowledge delay slot for jump instructions
This commit is contained in:
AJR 2020-01-21 19:51:43 -05:00
parent aed342f430
commit f807101c57
1 changed files with 47 additions and 33 deletions
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80
src/devices/cpu/gigatron/gigatrondasm.cpp
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@ -43,11 +43,12 @@ u32 gigatron_disassembler::opcode_alignment() const
offs_t gigatron_disassembler::disassemble(std::ostream &stream, offs_t pc, const gigatron_disassembler::data_buffer &opcodes, const gigatron_disassembler::data_buffer &params)
{
u16 inst = opcodes.r16(pc);
u32 flags = 0;
if (inst >= 0xe000)
{
// Jump instructions use special format
util::stream_format(stream, "%-6s", s_jumps[(inst & 0x1c00) >> 10]);
util::stream_format(stream, "%-5s", s_jumps[(inst & 0x1c00) >> 10]);
if ((inst & 0x1c00) == 0)
stream << "y,";
@ -57,7 +58,7 @@ offs_t gigatron_disassembler::disassemble(std::ostream &stream, offs_t pc, const
if ((inst & 0x1c00) == 0)
util::stream_format(stream, "$%02x", inst & 0x00ff);
else
util::stream_format(stream, "$%04x", (pc & 0x3f00) | (inst & 0x00ff));
util::stream_format(stream, "$%04x", ((pc + 1) & 0x3f00) | (inst & 0x00ff));
break;
case 0x0100:
@ -72,65 +73,78 @@ offs_t gigatron_disassembler::disassemble(std::ostream &stream, offs_t pc, const
stream << "in";
break;
}
flags = STEP_OVER | step_over_extra(1);
}
else if ((inst & 0xe300) == 0xc100)
{
// This was originally an undefined store mode
util::stream_format(stream, "%-6s$%02x", "ctrl", inst & 0x00ff);
}
else if ((inst & 0xf300) == 0x0200)
stream << "nop";
else
{
util::stream_format(stream, "%-6s", s_ops[(inst & 0xe000) >> 13]);
// Bus data
switch (inst & 0x0300)
if ((inst & 0xe300) == 0xc100)
{
case 0x0000:
util::stream_format(stream, "$%02x", inst & 0x00ff);
if (inst >= 0xc000)
stream << ",";
break;
// This was originally an undefined store mode
util::stream_format(stream, "%-5s", "ctrl");
}
else
{
util::stream_format(stream, "%-5s", s_ops[(inst & 0xe000) >> 13]);
case 0x0100:
break;
// Bus data
switch (inst & 0x0300)
{
case 0x0000:
util::stream_format(stream, "$%02x", inst & 0x00ff);
if (inst >= 0xc000)
stream << ",";
break;
case 0x0200:
if (inst < 0xc000)
stream << "ac"; // implicit for store instruction
break;
case 0x0100:
break;
case 0x0300:
stream << "in";
if (inst >= 0xc000)
stream << ",";
break;
case 0x0200:
if (inst < 0xc000)
stream << "ac"; // implicit for store instruction
break;
case 0x0300:
stream << "in";
if (inst >= 0xc000)
stream << ",";
break;
}
}
// RAM source or store destination
if (inst >= 0xc000 || (inst & 0x0300) == 0x0100)
{
if ((inst & 0xe300) != 0xc100)
stream << "[";
switch (inst & 0x1c00)
{
case 0x0000: case 0x1000: case 0x1400: case 0x1800:
util::stream_format(stream, "[$%02x]", inst & 0x00ff);
util::stream_format(stream, "$%02x", inst & 0x00ff);
break;
case 0x0400:
stream << "[x]";
stream << "x";
break;
case 0x0800:
util::stream_format(stream, "[y,$%02x]", inst & 0x00ff);
util::stream_format(stream, "y,$%02x", inst & 0x00ff);
break;
case 0x0c00:
stream << "[y,x]";
stream << "y,x";
break;
case 0x1c00:
stream << "[y,x++]";
stream << "y,x++";
break;
}
if ((inst & 0xe300) != 0xc100)
stream << "]";
}
// Non-accumulator destinations
@ -143,5 +157,5 @@ offs_t gigatron_disassembler::disassemble(std::ostream &stream, offs_t pc, const
}
}
return 1;
return 1 | flags | SUPPORTED;
}