Version 0.16.3 | Changelog
ZX-M8XXX (ZX Matrix) is a vanilla JavaScript ZX Spectrum emulator with an integrated debugger designed for reverse engineering and development. No build tools, no dependencies - just serve from any webserver, local or remote.
Writing a tool that drives it? Read M8XXX.md — what the emulator offers, how to ask it for the API of the build you are talking to, and the rules that are not discoverable from the API.
- Full Z80 CPU emulation (all documented + undocumented opcodes)
- 48K, 128K, +2, +2A, +3, Pentagon, Pentagon 1024, and Scorpion ZS 256 machine support
- Memory banking and contention emulation
- Pixel-perfect ULA video timing with border effects
- ULAplus extended palette (64 colors, HAM256 raster effects)
- ULA snow (optional) — the 48K refresh-cycle fault that fills the screen with noise when I points at $40-$7F
- ULA ink edge skew — the Ferranti mux switches into ink late, so an ink pixel is narrower than a paper one (48K/128K/+2 only, as with snow)
- AY-3-8910 sound chip emulation (stereo modes: Mono/ABC/ACB)
- PSG file export (record AY music with player source)
- SNA/Z80/SZX snapshot loading/saving, nine save-state slots
- Rewind (Ctrl+Left) — step back through the last minute of play
- Kempston, Sinclair 1/2, Cursor and custom-key joysticks (numpad or gamepad)
- TAP/TZX tape loading (instant or real-time with border stripes and sound)
- WAV tape loading (real recordings of tapes, including turbo loaders)
- Tape SAVE and MIC recording — a program's own SAVE is captured to a new tape
- Multiple tape slots (swap sides or games without reloading)
- Auto Load: automatic LOAD "" for tapes, TR-DOS boot for disks (turbo block handoff)
- TRD/SCL disk image support (TR-DOS format) with boot injection
- DSK disk image support (+3 µPD765 FDC, standard and extended CPC DSK format)
- MGT disk image support (DISCiPLE/+D WD1772 FDC, NMI snapshot button)
- MDR Microdrive cartridge support (Interface 1, 8-drive daisy chain)
- OPD disk image support (Opus Discovery WD1770 FDC + MC6821 PIA, memory-mapped I/O)
- Multi-drive support: BetaDisk 4 drives (A-D), FDC 2 drives (A-B), +D 2 drives (A-B), Microdrive 8 drives (1-8), Opus 2 drives (A-B), simultaneous tape+disk
- Didaktik 40/80 MDOS disk images (read and edit in the Explorer; the interface itself is not emulated)
- ZIP archive support
- RZX recording and playback
- Kempston Joystick (numpad) with extended buttons support
- Kempston Mouse with wheel support and swappable L/R buttons
- Hardware gamepad support (USB/Bluetooth via Gamepad API), autofire
- Keyboard: Ctrl=Caps Shift, Alt=Symbol Shift (works with any layout), on-screen ZX keyboard
- Keyboard ghosting, as on real hardware (optional — three keys can conjure a fourth)
- Unified breakpoint system (execution, memory read/write, port I/O)
- Execution trace with history navigation (10,000 instructions)
- Memory region marking (code/data/text/graphics)
- Auto memory mapping (detect regions during execution)
- Memory heatmap visualization
- Disassembly-toolchain exports (SkoolKit
.ctl, Ghidra.csv, sjasmplus.sym) - Runtime profiler with hotspot detection and a visual call graph
- Code Path recording (diff which code ran between two runs)
- Struct mapper (field accesses at offsets from IX/IY or a fixed base)
- Signature packs for auto-labelling, with a GitHub pack browser
- Shadow screen view, layout splitters, Ctrl+G goto palette
- Labels with import/export
- Cross-references (XRefs) tracking
- Subroutine detection and marking
- Code folding (collapse/expand subroutines and custom blocks)
- Bookmarks for quick navigation
- Runtime call stack tracking (CALL/RST/INT/RET)
- Breakpoint ΔT counter (cycle-exact timing measurement)
- Undo/Redo support
- Pattern search with wildcards
- Project save/load (complete session state)
- Headless automation API (
window.zxDebug) for scripted runs — see docs/automation.md
- Integrated Z80 assembler (sjasmplus-compatible)
- Multi-file projects with virtual file system
- LUA/ENDLUA scripting (sjasmplus-compatible, via fengari)
- Syntax highlighting
- Search/replace across all files
- Output: SAVEBIN, SAVESNA, SAVETAP, SAVETRD, EMPTYTRD, EXPORT
zx.*Lua helpers (trdimage_create/add_file, save_snapshot_sna)- Import foreign sources: ALASM, TASM, STORM, ADS, GENS, Zeus, Pasmo
- Source beautifier (case, number base, alignment, jump labels)
- Code snippets (built-in and your own)
- MD5 checksum verification
- Debug injection at entry point (with label export to debugger)
- Graphics Viewer for sprite search
- Memory Watches (up to 10 addresses)
- POKE Manager (native JSON and community
.pokcheat files) - POKE Search (find a game's lives/ammo variable by narrowing snapshots)
- Screenshot, GIF and animation export (with loop detection)
- Text Scanner for string search
- Programmer Calculator (hex/dec/oct/bin)
- Compare Tool (snapshots, binaries, emulator state, and memory against memory — by 64K address or by RAM bank)
- Explorer (TAP, TZX, SNA, Z80, SZX, RZX, TRD, SCL, MGT, DSK, MDR, OPD, D40/D80, ZIP — BASIC decoder, disassembly, hex dump, disk map visualization, per-format editors, SPECSCII catalogue banners)
- Game Mapper (capture rooms, stitch into navigable map grid, blend screenshots, save/load JSON, export PNG)
- OCR Text Ripper (screen text recognition, custom cell size 4–8×4–16 px, grid origin offsets, font extraction from memory, multi-charset support, character map templates, bulk glyph delete, capture-known mode)
- Z80 Opcodes reference
python run-tests.py runs every browser test suite headlessly and prints one table
(33 suites, ~5,100 asserts). Filter with python run-tests.py asm disk, --list to
see them, --all to include the long-running fuse-test.
- Place ROM files in
roms/directory:48.rom- ZX Spectrum 48K (16KB, required)128.rom- ZX Spectrum 128K (32KB, optional)plus2.rom- ZX Spectrum +2 (32KB, optional)plus2a.rom- ZX Spectrum +2A (64KB, optional)plus3.rom- ZX Spectrum +3 (64KB, optional)pentagon.rom- Pentagon 128K (32KB, optional)scorpion.rom- Scorpion ZS 256 (64KB, optional)trdos.rom- TR-DOS 5.03/5.04t (16KB, for disk images)plusd.rom- DISCiPLE/+D (8KB, optional)if1.rom- Interface 1 (8KB, optional)opus.rom- Opus Discovery (8KB, optional)
- Open
index.htmlin a modern browser - Click Help button for comprehensive documentation
| Format | Description |
|---|---|
| D40/D80 | Didaktik 40/80 MDOS disk image (Explorer only) |
| DSK | +3 disk image (standard and extended CPC DSK) |
| MDR | Interface 1 Microdrive cartridge |
| MGT | DISCiPLE/+D disk image |
| OPD | Opus Discovery disk image |
| RZX | Input recording |
| SCL | TR-DOS file archive |
| SNA | Snapshot (48K/128K) |
| SZX | Spectaculator snapshot format |
| TAP | Tape format (instant or real-time loading) |
| TRD | TR-DOS disk image |
| TZX | Extended tape format (turbo, pure tone, loops) |
| WAV | Tape audio recording |
| Z80 | Snapshot (v1, v2, v3 with compression) |
| ZIP | Archive support |
- Real-time tape loading (work in progress): Some copy protection schemes work, others don't yet. Standard loaders and many turbo loaders work; complex protection may fail. Flash load (instant) mode is more reliable.
- RZX playback: Partial support - some recordings may desync due to timing differences
- Z80 save uncompressed: Z80 snapshots are saved without RLE compression for maximum compatibility (~131KB for 128K, ~49KB for 48K)
- ULAplus raster effects: HAM256 and similar multi-entry palette effects work correctly. Per-scanline effects (like ULAplusDemo border stripes) may show minor paper/border desync at edges.
GPL-3.0
Test Programs: The test programs in the tests/ folder (z80ccf, z80doc, z80docflags, etc.) are copyright of their respective authors and included for emulator validation purposes only.
Based on Z80 documentation and Fuse emulator behavior.
Inspired by: JSSpeccy 3, EmuzWin, Swan, ZXMAK2
- dcorp80 — ES module extraction approach (PR #1)
- introspec — his LUA script library for sjasmplus was the real-world test case that drove the assembler's LUA support
- xLook by Dmitry Kozlov (HalfElf) & Alexander Medvedev — the ALASM/TASM detokenizers used by Import Foreign are ports of the xLook v0.2b FAR plugin sources, kindly provided by the author
- fengari — Lua 5.3 VM in JavaScript, powering the assembler's LUA/ENDLUA blocks (MIT license)
- pako — zlib decompression (MIT + Zlib license)
- ZX82 System — ZX Spectrum display font by Paul van der Laan
