https://github.com/davidjenni/6502-emu

6502 CPU emulator in rust
https://github.com/davidjenni/6502-emu

6502 6502-emulation emulator rust

Last synced: about 17 hours ago
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6502 CPU emulator in rust

• Host: GitHub
• URL: https://github.com/davidjenni/6502-emu
• Owner: davidjenni
• License: mit
• Created: 2023-08-30T00:52:29.000Z (about 1 year ago)
• Default Branch: main
• Last Pushed: 2023-10-22T23:50:28.000Z (12 months ago)
• Last Synced: 2024-04-15T06:43:49.303Z (6 months ago)
• Topics: 6502, 6502-emulation, emulator, rust
• Language: Rust
• Homepage:
• Size: 155 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Contributing: CONTRIBUTING.md
  • License: LICENSE
  • Code of conduct: CODE_OF_CONDUCT.md

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README

        
# 6502 CPU emulator in rust

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![MOS6502 in a 40 pin plastic package](/assets/MOS%206502%20DIP40-small.jpg)

![MOS6502 die](/assets/MOS_6502_die-small.jpg)

The [MOS 6502 CPU](https://en.wikipedia.org/wiki/MOS_Technology_6502) spawned

the microcomputer age in the mid 1970s, and was the common runtime for

one of MSFT's earliest products, MSBASIC.

While the original first MS product targeted the Altair 8080,

it was the abundance of 6502-based computers (Apple I & II, PET, CBM, etc.)

that made MSBASIC truly popular and considerably helped the MSFT brand in its early days.

Running MSBASIC on a rust-based CPU emulator on a VM in the Azure cloud is a geeky,

but also educational showcase how the whole computer industry has evolved over the past 50 years.

![rust crustacean](/assets/crabby.png)

This project is also my first foray into programming with rust; the code in this repo is the journey

to get hopefully close to idiomatic rust programming.

My notes on and sources for [the journey to rust](/docs/Learning_Rust.md).

## Run via cargo

```bash

A 6502 emulator written in Rust

Usage: r6502.exe [OPTIONS] [COMMAND]

Arguments:

  [COMMAND]

          [default: run]

          [possible values: run, debug]

Options:

  -b, --binary 

          Path to binary file to load and run

  -f 

          File format of the binary file to load

          Possible values:

          - bin: Plain binary with no header, little endian byte order

          - prg: Like a bin file, but with a 16 byte header that indicates the load address

  -l, --load-address 

          Load address (u16) for binary to be loaded to (inferred for .prg); if no start_addr it is also used as start address

  -s, --start-address 

          Start address (u16) for binary to be started with; can be hex address in 0x1234 format

  -r, --read-only

          loaded binary is read-only in memory (simulate ROM)

  -h, --help

          Print help (see a summary with '-h')

  -V, --version

          Print version

```

With an empty program, the reset vector 0xFFFE points to a BRK instruction,

halting the "program" after one instruction.

```bash

cargo run --bin r6502 --

No binary file specified, running empty program with single BRK instruction

PC: FFFE: A: 00 X: 00 Y: 00 S: 00000000 SP: 01FC

Instructions: 1; Cycles: 7; Clock speed: 1.045 MHz

Program finished after 6 μs:

done.

```

Debugging with step and disassembly listing is also possible.

```bash

cargo run --bin r6502 -- debug -b ./cli/tests/assets/euclid_gcd.prg -s 0x0200

Loaded 476 bytes at address 0040; read-only mem=false

PC: 0200: A: 00 X: 00 Y: 00 S: 00000000 SP: 01FF

(dbg)> di

  0200 LDA $40

  0202 SEC

  0203 SBC $41

  0205 BEQ $12 (0219)

  0207 BMI $05 (020E)

  0209 STA $40

  020B JMP $0202

  020E LDX $40

  0210 LDY $41

  0212 STX $41

(dbg)>

(dbg)> s

PC: 0202: A: 78 X: 00 Y: 00 S: 00000000 SP: 01FF

(dbg)>

PC: 0203: A: 78 X: 00 Y: 00 S: 00000001 SP: 01FF

(dbg)> h

Usage:

  step (s)          - step one instruction

  disassemble (di)  - disassemble instructions from current PC

  continue (c)      - continue execution

        - repeat last command

  quit (q)          - quit debugger

(dbg)>

```

## Feedback & Questions

Please use the issues tracker in the home repo: 

## Contributing

This project will welcome contributions in the near future. At this stage, we're not ready for contributions,

but do welcome your suggestions via this repository's issue tracker.

Information on how to setup a local dev environment is also detailed in this document.

See details in [CONTRIBUTING](CONTRIBUTING.md)

### Code of Conduct

See details in [CODE_OF_CONDUCT](CODE_OF_CONDUCT.md)