https://github.com/inindev/65c02_emu
65c02 emulator
https://github.com/inindev/65c02_emu
6502 6502-emulator
Last synced: 8 days ago
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65c02 emulator
- Host: GitHub
- URL: https://github.com/inindev/65c02_emu
- Owner: inindev
- License: gpl-3.0
- Created: 2018-09-09T21:07:43.000Z (almost 8 years ago)
- Default Branch: main
- Last Pushed: 2026-02-15T21:19:06.000Z (5 months ago)
- Last Synced: 2026-02-16T04:21:46.125Z (5 months ago)
- Topics: 6502, 6502-emulator
- Language: JavaScript
- Homepage:
- Size: 107 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# W65C02S Emulator
A complete W65C02S (CMOS 6502) processor emulator written in JavaScript with an interactive trainer/debugger interface.
🚀 **[Try it live!](https://inindev.github.io/65c02_emu/)**
🧪 **[Klaus Dormann 6502 Test Suite](https://inindev.github.io/65c02_emu/kd_test/)**
## Features
- **Full W65C02S instruction set** - All 65C02 opcodes including CMOS-specific instructions
- **Interactive trainer/debugger** - Visual register inspector, memory viewer, single-step execution
- **Browser-based** - No installation required, runs entirely in the browser
- **Validation tested** - Passes Klaus Dormann's comprehensive 6502 functional test suite (~88M cycles)
## Quick Start
### Online Demo
Try the emulator immediately: **https://inindev.github.io/65c02_emu/**
### Local Development
1. **Start the Web Server**
```bash
sh http_server.sh
```
This starts a local HTTP server on port 8000.
2. **Open the Trainer**
Navigate to: **http://localhost:8000/**
## Project Structure
```
├── index.html # Main trainer/debugger interface
├── w65c02s.js # W65C02S CPU emulator core
├── ram.js # Memory implementation
├── display.js # UI and debugger logic
├── kd_test/ # Klaus Dormann test harness
│ ├── README.md # Test suite documentation
│ ├── index.html # Test runner interface
│ ├── test_harness.js # Test execution engine
│ └── test_ui.js # Test UI controller
└── test/ # Legacy test interface
├── index.html
└── tests.js
```
## Using the Trainer/Debugger
The main interface (`index.html`) provides:
### Register Inspector
- View and edit all CPU registers (PC, A, X, Y, SP)
- Monitor processor flags (N, V, B, D, I, Z, C)
- Click any value to edit directly
### Memory Viewer
- Hexadecimal memory dump
- Navigate to any address
- View disassembled instructions
### Execution Controls
- **Step** - Execute one instruction
- **Run** - Continuous execution
- **Stop** - Halt execution
- **Reset** - Reset CPU to initial state
### Code Entry
- Enter 6502 assembly code or hex bytes
- Load programs into memory
- Execute from any address
## Validation
This emulator has been validated against Klaus Dormann's comprehensive 6502 functional test suite, which exercises:
- All instruction opcodes and addressing modes
- Flag behavior (N, V, Z, C)
- Stack operations
- Interrupt handling
See [kd_test/README.md](kd_test/README.md) for details on running the test suite.
**Test Results:**
- ✅ 6502 Functional Test: **PASSED** (87,947,229 cycles)
- ✅ 65C02 Extended Opcodes: **PASSED**
## Architecture
### W65C02S Core (`w65c02s.js`)
The emulator implements:
- All 17 addressing modes (absolute, zero page, indexed, indirect, etc.)
- Complete instruction set including 65C02 extensions
- Accurate flag behavior and timing
- Stack operations with proper push/pull semantics
Key classes:
- `W65C02S` - Main CPU emulator
- `Register6502` - Register file (A, X, Y, PC, SP, flags)
- `Flags6502` - Processor status register
### Memory Model (`ram.js`)
- 64KB addressable memory space
- Read/write operations
- 16-bit word operations (little-endian)
### Display/Debugger (`display.js`)
- Real-time register updates
- Memory visualization
- Disassembly view
- Execution control
## Development
### Browser Compatibility
Works in all modern browsers with ES6 support:
- Chrome/Edge
- Firefox
- Safari
### Local Development
No build process required - pure JavaScript:
```bash
# Start local server
sh http_server.sh
# Or use Python's built-in server
python3 -m http.server 8000
```
## Technical Details
### W65C02S Specifications
- **Architecture**: 8-bit CMOS microprocessor
- **Address Space**: 64KB (16-bit addressing)
- **Registers**: A (accumulator), X, Y (index), PC (program counter), SP (stack pointer)
- **Flags**: N (negative), V (overflow), B (break), D (decimal), I (interrupt), Z (zero), C (carry)
- **Stack**: 256 bytes (0x0100-0x01FF), descending
### References
- [W65C02S Datasheet](http://www.wdesignc.com/wdc/documentation/w65c02s.pdf)
- [6502 Flag Tutorial](http://www.6502.org/tutorials/vflag_html)
- [Klaus Dormann Test Suite](https://github.com/Klaus2m5/6502_65C02_functional_tests)
## Known Bugs Fixed
- ✅ **PHP instruction** - Now correctly sets B flag when pushing status to stack
- ✅ **BRK instruction** - Now properly pushes PC+2 and status, sets flags, jumps to IRQ vector
## License
GNU General Public License v3.0
Copyright © 2018 John Clark
See [LICENSE](LICENSE) for full license text.
## Contributing
Bug reports and pull requests welcome! This emulator aims for cycle-accurate emulation of the W65C02S.
### Testing Changes
Always run the Klaus Dormann test suite after making changes:
```bash
# See kd_test/README.md for setup
cd kd_test
# Download test binaries (see README)
# Open http://localhost:8000/kd_test
# Load and run tests
```
## Credits
- **CPU Implementation**: John Clark
- **Test Suite**: Klaus Dormann ([6502_65C02_functional_tests](https://github.com/Klaus2m5/6502_65C02_functional_tests))
- **W65C02S Specifications**: Western Design Center ([Datasheet](https://www.westerndesigncenter.com/wdc/documentation/w65c02s.pdf))