: Generates meaningful labels for jump targets and memory addresses instead of just raw hex values.
: Often include an integrated assembler and an emulator.
Some legacy programs alter their own instructions in RAM during execution to save CPU cycles. A static disassembler cannot predict these runtime changes.
Do you need to the code afterward, or are you just analyzing how it works? Share public link
: 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 z80 disassembler online full
A standard output matrix from a full disassembler splits the interface into clear, scannable columns: Memory Address Machine Code (Hex) Assembly Instruction Description / Context 0000 F3 DI Disable interrupts 0001 31 FF C0 LD SP, $C0FF Initialize stack pointer 0004 AF XOR A Clear Accumulator to 0 0005 D3 01 OUT ($01), A Send 0 to hardware port 01 0007 18 FE JR -2 Infinite loop (Jump Relative) Key Decoding Patterns to Watch For:
Load your targeted .bin , .rom , or .hex file, or paste raw hexadecimal text into the input field.
If you have a ROM file (e.g., a classic game dump) and want to see how it works, here is the typical workflow:
The Z80 has many instructions that were never officially documented but are used heavily in game coding (e.g., IX/IY register manipulation). A good disassembler, like dZ80 (mentioned here as a reference for advanced capabilities), handles these correctly. : Generates meaningful labels for jump targets and
Reading code filled with hardcoded memory addresses like CALL $3A2F is incredibly difficult. A full disassembler automatically generates relative labels (e.g., LABEL_3A2F: ) for jump targets ( JP , JR ) and subroutines ( CALL ). This allows you to trace execution paths seamlessly. 4. Code vs. Data Separation
Once the disassembly is clean, a full online utility allows you to export the result as a text file ( .asm or .txt ). This file can then be fed directly into a modern Z80 assembler (like SJASMPlus or Pasmo) to recompile the code after you make your modifications. Popular Online Z80 Disassemblers to Try
Good support for all Z80 undocumented instructions, which are vital for reverse-engineering older software.
When searching for a complete solution, look for these critical features: 1. Complete Instruction Set Support A static disassembler cannot predict these runtime changes
This comprehensive guide explores what constitutes a "full" online Z80 disassembler, how to use these tools effectively, and the best platforms available today. What Makes an Online Z80 Disassembler "Full"?
Do you have the code as a or a hexadecimal text string ?
: A robust multi-architecture platform. By selecting "Z80" from the architecture list, you can upload binary files or paste hex strings to get a professional, searchable text listing. Key Features to Look For
Open the resulting .asm file. Because disassembly produces a line-for-line translation of the machine code, you will see endless lists of instructions:
The Z80 processor features dozens of undocumented instructions that developers historically used to squeeze extra performance out of the chip (such as splitting index registers like IX and IY into 8-bit halves: IXH and IXL ). A complete disassembler must accurately decode these non-standard instructions. 4. Syntax Customization
Blocks of ASCII characters (often readable text strings in the right-hand panel of the tool).