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If you change the selection by double-clicking in one of the side
windows (References, Notes, Symbols, Messages) and then attempt
to navigate with the arrow keys, the program will appear to hang
briefly, then jump to the start or end of the project and shift the
window focus to something else (like the Help menu in the menu bar).

For reasons I don't fully understand, the behavior is fixed by
removing unnecessary calls to codeListView.Focus().  The calls were
intended to shift input focus to the main ListView, but they're no
longer necessary, and appear to upset WPF.

(issue #113)

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Features - Installation - Getting Started - About the Code

6502bench is a code development "workbench" for 6502, 65C02, and 65802/65816 code. It currently features one tool, the SourceGen disassembler, and runs on Windows 7 or later.

You can download the source code and build it yourself, or click the Releases tab for downloads with pre-built binaries.


SourceGen converts machine-language programs to assembly-language source code. It has most of the features you will find in other 6502 disassemblers, as well as many less-common ones.

Key Features

  • Fully interactive point-and-click GUI. Define labels, set addresses, add comments, and see the results immediately. Add multi-line comments and have them word-wrapped automatically. Create inline visualizations of embedded bitmaps and wireframe data, and define animated sequences.
  • Sophisticated static analysis. The disassembly engine traces code execution, automatically finding all instructions reachable from defined entry points. Changes to the processor status flags are tracked, allowing identification of branches that are always/never taken, accurate cycle count listings, and easier analysis of 65816 code with variable-width registers.
  • Easy generation of assembly source code for popular cross-assemblers (currently 64tass, ACME, cc65, and Merlin 32). Cross-assemblers can be invoked from the GUI to verify correctness.
  • Symbols and constants are provided for ROM and operating system entry points on several popular systems.
  • Project files are designed for sharing and collaboration.

SourceGen has been used to disassemble software for the Apple II, NES (Nintendo Entertainment System), Atari 2600 VCS, and coin-op arcade systems. Video demos of basic features and visualizations are available.

Features in Detail


  • Support for 6502, 65C02, and 65816, including undocumented opcodes and the W65C02 extensions.
  • Code tagging mechanism allows manual identification of code start/stop points and inline data.
  • Editable labels are generated for every branch destination and data target.
  • Automatic detection and classification of character strings and runs of identical bytes.
  • Symbol files for ROM entry points, operating system constants, and other platform-specific data are stored in plain text files loaded at runtime.
  • Extension scripts can be defined that automatically reformat code and identify inline data that follows a JSR, JSL, or BRK.

User interface:

  • "Infinite" undo/redo of all operations.
  • Cross-reference tables are generated for every branch and data target address, as well as for external platform symbols.
  • Instruction operand formats (hex, decimal, binary, character, symbol) can be set for individual instructions. References to nearby symbols are offset, allowing simple expressions like "addr + 1".
  • Data areas can be formatted in various formats, including individual bytes, 16-bit and 24-bit words, addresses, or strings. Multiple character encodings are supported, including ASCII, high ASCII, C64 PETSCII, and C64 screen codes.
  • Zero-page variables can be given different labels at different points in the program.
  • Multi-line comments can be "boxed" for an authentic retro feel.
  • Notes can be added that aren't included in generated output. These also function as color-coded bookmarks. Very useful for marking up a work in progress. Similarly, symbols can be marked as uncertain by adding a '?' that is automatically stripped away during code generation.
  • Instruction reference data, such as CPU cycles and flags modified, are shown along with a description of the opcode's function. Very useful when encountering rarely-used undocumented instructions.
  • Various aspects of the code display can be reconfigured, including upper/lower case, pseudo-opcode naming, and expression formats. These choices are not part of the project definition, so everyone can view a project according to their own personal preferences.

Code generation:

  • Labels can be global or local. Use non-unique labels like "@Loop" for clarity. Labels will be promoted from local to global or renamed to be unique as required by each assembler.
  • Symbols may be exported from one project and imported into another to facilitate multi-binary disassembly.
  • Listings can be generated in HTML form for publication on the web. Many aspects of the output format can be configured. Inline visualizations are exported as GIF or animated GIF.


  • All project data is stored in text formats (primarily JSON).
  • The project file includes nothing from the data file but a CRC. This may allow the project to be shared without violating copyrights (subject to local laws).
  • Handy tools: file slicer, file concatenator, CPU instruction reference chart, ASCII chart, file hex dump.
  • The OMF converter tool can be used to disassemble Apple IIgs executables.


While the 65816 CPU is fully supported, SourceGen can be awkward to use with the large binaries that the expanded architecture makes possible. The disassembly is displayed in a single scrolling window, so projects for binaries larger than about 100KB become difficult to navigate. There may also be performance issues at larger sizes. SourceGen currently imposes an arbitrary 1MB limit on the data file.

Generating output larger than 64KB requires some target-specific directives, e.g. for defining OMF segments for Apple IIgs executables. SourceGen does not currently support these. While you can generate source for a binary larger than 64KB, most cross-assemblers will fail to assemble it without additional edits.

The zero-page argument for the Rockwell BBR/BBS instructions cannot be formatted.

To learn about other areas for potential future development, visit the wiki section for the current "TO DO" list.

To learn about the past, check the change log.


There is currently no installer -- just unzip the archive and run the "SourceGen.exe" executable. The data files used by the program are found automatically in the directory where the .EXE lives.

You need to have Microsoft .NET Framework v4.6.2 or later installed. Most people will already have this. If SourceGen doesn't seem to want to start, download the latest version (currently v4.8) directly from Microsoft. The framework requires Win7 SP1, Win8.1, or Win10 updated through at least the Anniversary Update (1607). (One user who had trouble with the 4.7.2 installer was able to get the 4.6.2 installer to work.)

SourceGen does not currently run on Linux or Mac OS X. My understanding is that .NET apps don't work under WINE, so it can only be run on a full Windows system emulation.

(SourceGen versions 1.0 and 1.1 used the WinForms API, which has been implemented for Mono, but after encountering significant bugs that I wasn't able to work around I abandoned the approach and switched to WPF. Besides working better under Windows, WPF uses a more modern approach (XAML) that may ease the transition to a cross-platform GUI API like Avalonia.)

Getting Started

The best way to get started is by working through the tutorial, available on the web site. I strongly recommend doing this, as some aspects of SourceGen are non-obvious.

Several examples of completed projects are included in the SourceGen distribution. Most of these are alongside the original source code, allowing a direct comparison between how the code was written and how SourceGen can format and display it.

About the Code

The source code is licensed under Apache 2.0 (, which makes it free for use in both open-source programs and closed-source commercial software. The license terms are similar to BSD or MIT, but with some additional constraints on patent licensing. (This is the same license Google uses for the Android Open Source Project.)

Images are licensed under Creative Commons ShareAlike 4.0 International (

For additional details, see the source code notes.