Butterfly 6502-based emulator

What is this?

It's an emulator designed to emulate a 6502 CPU and various peripherals.

Why is this?

Because I thought it would be fun, I was also inspired by Ben Eater's excellent 6502 video series. Originally I had wanted to create a breadboard computer, but realized that I didn't have the extra cash for things like logic analyzers or oscilloscopes. Besides, emulating in software gives me flexibility to create whatever hardware I want!

Building

Build like you would any other Rust project:

cargo build

Running

A modified version of Ben Eater's blink.asm is provided in demos/blink.asm, and will automatically run by simply running the following:

cargo run

Demos

There are a few demo programs included right now, and they all work (yay!). You can read more about them in demos/README.md. Anyway, here's how to run them.

blink.asm

cargo run -- -r demos/blink.bin (you can add -d to print each instruction to stdout, not recommended with this demo)

multiply10-blink.asm

cargo run -- -r demos/multiply10-blink.bin (you can add -d to print each instruction to stdout, not recommended with this demo)    

multiply10-noblink.asm

cargo run -- -r demos/multiply10-noblink.bin -d

decimal-test.asm

cargo run -- -r demos/decimal-test.bin (you can add -d to print each instruction to stdout, not recommended with this demo)    

Benchmarking

By running the following command, you can run a very very unsophisticated benchmark which uses blink.asm.

cargo run -- --benchmark

Command-line options

Usage: butterfly_emulator [OPTIONS]
Options:
  -r, --rom: The path to the ROM file to load (default: demos/blink.bin)
  -a, --address: The address to load the ROM at (default: 0xC000)
  -d, --debug: Enables debugging output (default: false)
  -v, --variant: The variant of the CPU to use
     - NMOS: The NMOS 6502 CPU
     - CMOS: The CMOS 65C02 CPU
     - NES: The NES CPU (Ricoh 2A03)
  -s, --speed: The speed to run the emulator at in Hz (default: 100)
  -b, --benchmark: Runs demos/blink.bin for 200,000,000 cycles and prints the results
  -h, --help: Prints the help message

Helpful Links

NesDev CPU wiki - Fantastic resource for 6502 information, specifically the NES version of the 6502.

mass:werk 6502 tools - A fully functional 6502 CPU emulator, assembler, and disassembler, as well as a great resource for 6502 instruction set internals