Z80 - Disassembler _top_

Pseudo-structure in C:

def recursive_disassemble(start, memory, visited): pc = start while pc < len(memory) and pc not in visited: visited.add(pc) insn, length = decode_one(pc, memory) print(f"pc:04X: insn") # simplistic flow analysis if "JP" in insn and "$" in insn: target = int(insn.split("$")[1], 16) if target not in visited: recursive_disassemble(target, memory, visited) break # unconditional jump elif "RET" in insn or "RETI" in insn or "RETN" in insn: break else: pc += length z80 disassembler

opcode_map = 0x00: ("NOP", 1), 0x01: ("LD BC, $%04X", 3), 0xC3: ("JP $%04X", 3), # ... full table omitted for brevity It powered everything from the Game Boy (custom

1. Introduction: Why the Z80 Still Matters The Zilog Z80, introduced in 1976, is one of the most influential microprocessors in history. It powered everything from the Game Boy (custom LR35902, a Z80 derivative) and the Sega Master System to the Sinclair ZX Spectrum, Amstrad CPC, MSX, and countless arcade machines. Even today, it thrives in embedded systems, retrocomputing, and hobbyist scenes. It lets you peer into the minds of

In the world of retrocomputing, a reliable Z80 disassembler is a time machine. It lets you peer into the minds of 1980s programmers, decode their clever memory-saving tricks, and preserve digital history—one opcode at a time.

To understand a Z80 binary—whether to reverse-engineer a classic game, patch a ROM, or debug vintage firmware—you need a disassembler. But a disassembler is not merely a "binary-to-text" converter. It is a lens through which we reconstruct intent, control flow, and data structures from raw machine code.

def decode_one(pc, memory): op = memory[pc] if op in opcode_map: mnemonic, length = opcode_map[op] if length == 3: operand = memory[pc+1] | (memory[pc+2] << 8) return (mnemonic % operand, length) return (mnemonic, length) else: return (".db $%02X" % op, 1)