z80dasm is a command-line disassembler for the Z80 and compatibles. It is the tool of choice for serious reverse-engineering projects.
LD A, 01h LD B, 02h ADD A, B
Even with a full-featured online tool, reverse engineering 8-bit binaries presents unique challenges:
The core Z80 instruction set consists of single-byte opcodes. For example: 00 = NOP (No Operation) C9 = RET (Return from Subroutine) 3E xx = LD A, xx (Load immediate value into Accumulator) 2. Prefix Bytes (Multibyte Instructions) z80 disassembler online full
Modding, translating, or fixing bugs in classic ZX Spectrum, ColecoVision, or Sega Master System games.
A does not just translate bytes; it intelligently interprets the code. Key features of a high-quality disassembler include:
: If you are interested in how the machine code is structured, the Z80 Decoding Guide explains the octal-based patterns used by the CPU. Z80 CPU User Manual - Zilog z80dasm is a command-line disassembler for the Z80
Refine the output by isolating code from data. Note the memory addresses where the valid code ends and the data tables begin. Use the tool's configuration panel to mark those ranges as Data or ASCII . This forces the engine to parse those bytes cleanly without generating corrupt assembly instructions. 5. Export and Re-Assemble
A disassembler is a reverse-engineering tool. It performs the exact opposite function of an assembler.
A performs the inverse operation of an assembler. While an assembler takes human-readable mnemonics (like LD A, 05h ) and turns them into machine code ( 3E 05 ), a disassembler takes those raw bytes and translates them back into mnemonics. For example: 00 = NOP (No Operation) C9
A comprehensive online disassembler often integrates more than just a text output. Key features found in advanced implementations include: GitHub - cormacj/z80-smart-disassembler
Binary files rarely contain pure executable code; they are frequently packed with graphics, audio data, text strings, and lookup tables. Advanced online disassemblers allow users to define specific memory ranges as "Data" (byte, word, or text definitions) or "Code" to prevent the engine from incorrectly turning sprite data into gibberish assembly instructions. Step-by-Step: How to Use an Online Z80 Disassembler
What is the ? (e.g., an arcade ROM, a ZX Spectrum game, custom embedded firmware)
The Ultimate Guide to Online Z80 Disassemblers: Reversing Zilog Architecture in Your Browser