Zinc64

Overview

zinc64 is a Commodore 64 emulator toolkit "with batteries included but swappable". It is designed to be used as a standalone emulator or a library used to build new emulators. The design philosophy allows for each component to be swapped out and replaced by different implementation. Therefore, special considerations were made to model interactions between chips without coupling them together.

It implements MOS 6510 CPU, MOS 6526 CIA, MOS 6581 SID, MOS 6567/6569 VIC chipset as well as various devices and peripherals available with C64.

Story

zinc64 was started as an exercise to learn Rust and explore Commodore 64 hardware in more detail. Somewhere around mid 2016 I needed to feed my 8-bit nostalgia so I picked up a working Commodore 64 (physical version) and started to assemble various accessories required to get software onto it. Soon enough I had picked up a copy of C64 Programmer's Reference Guide and the rest is now history.

2020 is bringing support for revised OpenGL port with console support and bare-metal environments, more specifically a bare-metal Raspberry Pi 3 port. See zinc64-rpi for an early preview.

Design

Feature std

zinc64-system crate works without the standard library, such as in bare-metal environments. To use zinc64-system in a #[no_std] environment, use:

[dependencies]
zinc64-system = { version = "0.9.0", default-features = false }

Extensibility

The emulator components may be swapped out by providing custom core::ChipFactory trait implementation. The default implementation of the core::ChipFactory trait is done through system::C64Factory. The chip factory object is passed into system::C64 component that provides core emulator functionality.

Here is an example how these components are used together:

    let config = Rc::new(Config::new(SystemModel::from("pal")));
    let chip_factory = Box::new(C64Factory::new(config.clone()));
    let mut c64 = C64::new(config.clone(), chip_factory).unwrap();
    c64.reset(true);

The four core traits used to model system operation are Chip, Cpu, Mmu and Addressable.

/// A chip represents a system component that is driven by clock signal.
pub trait Chip {
    /// The core method of the chip, emulates one clock cycle of the chip.
    fn clock(&mut self);
    /// Process delta cycles at once.
    fn clock_delta(&mut self, delta: u32);
    /// Handle vsync event.
    fn process_vsync(&mut self);
    /// Handle reset signal.
    fn reset(&mut self);
    // I/O
    /// Read value from the specified register.
    fn read(&mut self, reg: u8) -> u8;
    /// Write value to the specified register.
    fn write(&mut self, reg: u8, value: u8);
}

/// CPU is responsible for decoding and executing instructions.
pub trait Cpu {
    ...
    /// The core method of the cpu, decodes and executes one instruction. Tick callback is invoked
    /// for each elapsed clock cycle.
    fn step(&mut self, tick_fn: &TickFn);
    // I/O
    /// Read byte from the specified address.
    fn read(&self, address: u16) -> u8;
    /// Write byte to the specified address.
    fn write(&mut self, address: u16, value: u8);
}

/// Represents memory management unit which controls visible memory banks
/// and is used by CPU to read from and write to memory locations.
pub trait Mmu {
    /// Change bank configuration based on the specified mode.
    fn switch_banks(&mut self, mode: u8);
    // I/O
    /// Read byte from the specified address.
    fn read(&self, address: u16) -> u8;
    /// Write byte to the specified address.
    fn write(&mut self, address: u16, value: u8);
}

/// Addressable represents a bank of memory.
pub trait Addressable {
    /// Read byte from the specified address.
    fn read(&self, address: u16) -> u8;
    /// Write byte to the specified address.
    fn write(&mut self, address: u16, value: u8);
}

Since all system components with the exception of Cpu and Mmu implement Chip trait, interactions between chips and other components are limited to and handled through shared I/O lines/pins that are provided to chip constructors. This allows implementation of chips to be decoupled from each other.

Status

Roadmap

• v0.9 - opengl client
• v0.10 - rpi port
• v0.11 - floppy support

Getting Started

1. Install Rust compiler or follow steps @ https://www.rust-lang.org/en-US/install.html.

    curl https://sh.rustup.rs -sSf | sh
   

2. Clone this repository.

    git clone https://github.com/binaryfields/zinc64
   

   or download as zip archive

    https://github.com/binaryfields/zinc64/archive/master.zip
   

3. Build the emulator.

    cd zinc64
    cargo build --release --all
   

4. Run the emulator.

    ./target/release/zinc64
   

   or start a program

    ./target/release/zinc64 --autostart path
   

Windows Considerations

1. Install Microsoft Visual C++ Build Tools 2017. Select Visual C++ build tools workload.

Debugger

To start the debugger, run the emulator with '-d' or '--debug' option. Optionally, you can specify '--debugaddress' to bind to a specific address.

    ./target/release/zinc64 --debug

To connect to the debugger, telnet to the address and port used by the debugger.

    telnet localhost 9999

Debugger commands and syntax are modeled after Vice emulator. To see a list of available commands, type in the debugging session:

    help

or to get help on a specific command:

    help <command>

Radare2

Initial support for radare2 has been merged in version 0.3. To start the emulator with RAP server support, run

    ./target/release/zinc64 --rap 127.0.0.1:9999

and connect with

    radare2 -a 6502 -d rap://localhost:9999/1

Examples

I've included a number of examples from Kick Assembler that I've used to test various components of the emulator. They can be found in the bin folder of this repository and started with the emulator's autostart option.

    ./target/release/zinc64 --autostart bin/SineAndGraphics.prg

Tests

The cpu validation was performed with the help of Klaus2m5 functional tests for the 6502 processor

    ./target/release/zinc64 --console --loglevel trace bin/6502_functional_test.bin 

Keyboard Shortcuts

Credits

• Commodore folks for building an iconic 8-bit machine
• Rust developers for providing an incredible language to develop in
• Thanks to Rafal Wiosna for passing onto me some of his passion for 8-bit machines ;)
• Thanks to Klaus Dormann for his 6502_65C02_functional_tests, without which I would be lost
• Thanks to Dag Lem for his reSID implementation
• Thanks to Christian Bauer for his wonderful "The MOS 6567/6569 video controller (VIC-II) and its application in the Commodore 64" paper
• Thanks to Peter Schepers for his "Introduction to the various Emulator File Formats"
• Thanks to c64-wiki.com for my to go reference on various hardware components