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https://github.com/mre/mos6502
MOS 6502 emulator written in Rust
https://github.com/mre/mos6502
6502 cpu emulator retrocomputing
Last synced: 3 days ago
JSON representation
MOS 6502 emulator written in Rust
- Host: GitHub
- URL: https://github.com/mre/mos6502
- Owner: mre
- License: bsd-3-clause
- Created: 2017-10-08T15:18:40.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2024-10-21T08:51:42.000Z (3 months ago)
- Last Synced: 2024-12-30T06:08:42.331Z (10 days ago)
- Topics: 6502, cpu, emulator, retrocomputing
- Language: Rust
- Homepage:
- Size: 481 KB
- Stars: 84
- Watchers: 4
- Forks: 15
- Open Issues: 8
-
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yml
- License: LICENSE
- Authors: AUTHORS.txt
Awesome Lists containing this project
README
# mos6502
[](https://docs.rs/mos6502)
An emulator for the [MOS 6502 CPU](https://en.wikipedia.org/wiki/MOS_Technology_6502) written in Rust.
Tested and validated by [solid65](https://github.com/omarandlorraine/solid65).
It builds on stable Rust and supports `#[no_std]` targets.
## What is the MOS 6502?
> The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") is an 8-bit microprocessor that was designed by a small team led by Chuck Peddle for MOS Technology. [...]
>
> When it was introduced in 1975, the 6502 was the **least expensive microprocessor on the market** by a considerable margin. It initially sold for less than one-sixth the cost of competing designs from larger companies, such as the 6800 or Intel 8080. Its introduction caused rapid decreases in pricing across the entire processor market. **Along with the Zilog Z80, it sparked a series of projects that resulted in the home computer revolution of the early 1980s.**
Source: [Wikipedia](https://en.wikipedia.org/wiki/MOS_Technology_6502)
## How to use this library
```rust
use mos6502::memory::Bus;
use mos6502::memory::Memory;
use mos6502::instruction::Nmos6502;
use mos6502::cpu;
fn main() {
// Calculate the greatest common divisor of 56 and 49
// using Euclid's algorithm.
let zero_page_data = [56, 49];
let program = [
// (F)irst | (S)econd
// .algo
0xa5, 0x00, // Load from F to A
// .algo_
0x38, // Set carry flag
0xe5, 0x01, // Substract S from number in A (from F)
0xf0, 0x07, // Jump to .end if diff is zero
0x30, 0x08, // Jump to .swap if diff is negative
0x85, 0x00, // Load A to F
0x4c, 0x12, 0x00, // Jump to .algo_
// .end
0xa5, 0x00, // Load from S to A
0xff,
// .swap
0xa6, 0x00, // load F to X
0xa4, 0x01, // load S to Y
0x86, 0x01, // Store X to F
0x84, 0x00, // Store Y to S
0x4c, 0x10, 0x00, // Jump to .algo
];
let mut cpu = cpu::CPU::new(Memory::new(), Nmos6502);
cpu.memory.set_bytes(0x00, &zero_page_data);
cpu.memory.set_bytes(0x10, &program);
cpu.registers.program_counter = 0x10;
cpu.run();
// The expected GCD is 7
assert_eq!(7, cpu.registers.accumulator);
}
```
The same can be achieved, by compiling the euclid example yourself.
First install a 6502 assembler and linker, e.g. [cc65](https://cc65.github.io/cc65/).
```sh
brew install cc65
```
Then compile and link the assembly file:
```sh
cd examples/asm/euclid
ca65 euclid.a65
ld65 -C ../linker.cfg -o euclid.bin euclid.o
```
This will create a binary file `euclid.bin` that you can load into the emulator:
```rust
use mos6502::memory::Bus;
use mos6502::memory::Memory;
use mos6502::instruction::Nmos6502;
use mos6502::cpu;
use std::fs::read;
fn main() {
// Calculate the greatest common divisor of 56 and 49
// using Euclid's algorithm.
let zero_page_data = [56, 49];
// Load the binary file from disk
let program = match read("examples/asm/euclid/euclid.bin") {
Ok(data) => data,
Err(err) => {
println!("Error reading euclid.bin: {}", err);
return;
}
};
let mut cpu = cpu::CPU::new(Memory::new(), Nmos6502);
cpu.memory.set_bytes(0x00, &zero_page_data);
cpu.memory.set_bytes(0x10, &program);
cpu.registers.program_counter = 0x10;
cpu.run();
// The expected GCD is 7
assert_eq!(7, cpu.registers.accumulator);
}
```
## Credits
This started off as a fork of [amw-zero/6502-rs](https://github.com/amw-zero/6502-rs),
which seems to be [unmaintained](https://github.com/amw-zero/6502-rs/pull/36) at this point.