readme.md

micro_6502

A functioning 6502 microprocessor emulator.

This crate contains a library and an executable that also serves as an example.

Usage (library)

The main component of this library is the Emulator struct. This struct contains all the logic that runs the virtual CPU. To initialize a new instance of this struct, you will need a struct that implements the ReadWritable trait.

The ReadWritable trait provides a simple interface that allows the user to implement their own buses and connect the virtual CPU to peripherals. This library comes built in with a default ReadWritable struct—the Memory struct—that delivers a byte buffer that the CPU can access.

The following code instantiates a new virtual 6502 processor that runs the user-specified program:

use std::{fs::read, path::PathBuf};

use micro_6502::{
    emulator::Emulator,
    mem::{Memory, MEM_SIZE},
};

fn main() {
    assert!(
        std::env::args().len() == 2,
        "You need to provide a binary to run."
    );
    let program_bytes: [u8; MEM_SIZE] = {
        let args: Vec<String> = std::env::args().collect();
        let program_path: PathBuf = args[1].clone().try_into().expect("Cannot parse file path.");
        let bytes_vec = read(&program_path)
            .expect(format!("Cannot access the file at '{}'", program_path.display()).as_str());
        bytes_vec.try_into().expect(
            format!(
                "The file at '{}' must be {MEM_SIZE} bytes.",
                program_path.display()
            )
            .as_str(),
        )
    };

    let memory = Memory::new_from_bytes(program_bytes);
    let mut emulator = Emulator::new(Box::from(memory));
    emulator.run_until_break();

    println!("Registers: {}", emulator.get_regs());
}

Usage (executable)

To run a program using the emulator, run:

cargo run --features build-binary -- path/to/prog.bin

You can also specify the registers to initialize the program with:

cargo run --features build-binary -- path/to/prog.bin --regs x=3,y=2

Examples

There is an examples/ directory that contain some example programs.

Fibonacci

Computes the nth fibonacci number contained in the x register, outputting the result in the y register.

Note: due to the limitations of the architecture of the 6502 processor, the largest number you can generate is the 13th number in the sequence, i.e. 233.

cargo run --features build-binary -- examples/fibonacci.bin --regs x=(whatever)

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Made by dcas796