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! This repo is very out of date and I have not kept it up to date with any changes to the spec since January 2022 !

I have lost interest in this project and am unlikely to update it any time soon. The instruction set itself has changed and I believe there have been lots of changes to various devices in the interim. ROMs compiled since January of 2022 may not run in this emulator

Uxn-Lua

A port of the Uxn instruction set and Varvara virtual computer to the Lua language and the Love2D game engine. Is compatible with most ROMs, but runs at a much lower speed for cpu-intensive ROMs.

Installation

Running the unit tests requires Busted

Running this repository as a Love game requires Love 11+

Running uxn.lua as a standalone requires LuaJIT or a bitwise operations libray such as the standalone bitwise module

Quickstart

As a Love game

love .

Will try to load a file called boot.rom in the top-level directory.

love . somename.rom

Will try to load a file called somename.rom in the top-level directory.

Standalone use of the cpu

Uxn = require "uxn"
cpu = Uxn.Uxn:new()

-- Start the instruction pointer at the initial location
cpu.ip = 0x0100

-- Load some bytes into memory
values = {
	0x80, 0x13, -- LIT 0x13
	0x01, -- INC
	0x80, 0x37, -- LIT 0x37

	0x18, -- ADD

	0x00, -- BREAK
}

-- Copy the values offset by 255 so they start at the location of IP
for i = 1, #values do
	cpu.memory[i + 255] = values[i]
end

cpu:runUntilBreak()

-- Should print 75 or 0x4b
print(cpu.program_stack:pop())

CPU

Uxn:new([memory])

Optionally pass in a table that holds the contents of memory. Remember that this table is will be accessed starting at 0 unlike most Lua tables.

Uxn:runUntilBreak()

Run the CPU until it hits a BRK instruction (0x00).

Uxn:addDevice(num, device)

Adds a [Device] to the specified device number. See the Varvara docs for standard device numbers.

Devices

The device object stores 16 bytes of memory as well as providing callbacks to trigger when different ports are written to

Device:addPort(port, length, onRead, onWrite)

Device:readShort(addr)

Device:writeShort(addr, value)

Device:trigger

Jumps to the vector for this device and runs until it reaches a BRK instruction.

Examples

Create a device that prints to the console every time port 0x08 is written to.

local device = Device:new()

-- Add a byte port at 0x08
device:addPort(0x08, false, nil, function(byte)
	print("wrote a byte", byte, "to port 0x08")
end)

Attach a device to a cpu

local cpu = Uxn:new()

cpu:addDevice(num, device)

TODO

  • Add file writing
  • Audo
  • Implement debug properties of System device
  • Add datetime device