mirror of
https://github.com/mre/mos6502.git
synced 2024-11-28 22:51:26 +00:00
68 lines
2.5 KiB
Markdown
68 lines
2.5 KiB
Markdown
# mos6502
|
|
|
|
|
|
[](https://docs.rs/mos6502)
|
|
|
|
An emulator for the [MOS 6502 CPU](https://en.wikipedia.org/wiki/MOS_Technology_6502) written in Rust.
|
|
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::address::Address;
|
|
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();
|
|
|
|
cpu.memory.set_bytes(Address(0x00), &zero_page_data);
|
|
cpu.memory.set_bytes(Address(0x10), &program);
|
|
cpu.registers.program_counter = Address(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.
|