lj-ditrapani / 16-bit-computer-cpu-coffeescript

LJD 16-bit CPU in CoffeeScript

LJD 16-bit processor

For other implementations, see https://github.com/lj-ditrapani/16-bit-computer-specification.

Design:

• 16-bit CPU
• 16 X 16-bit registers and program counter (PC)
• Harvard architecture
• 2^16 = 65,536 ROM addresses (16-bit resolution)
• 2^16 = 65,536 RAM addresses (16-bit resolution)
• ROM and RAM are word-addressable
• A word is 16 bits (2 bytes)
• ROM + RAM: 128 KWords = 256 KB = 2 M-bit
• All instructions are 16 bits long
• 16 instructions (4-bit op-code)

The processor instruction set architecture (ISA) can be found in doc/ISA.md.

Usage

npm install ljd-16-bit-cpu

From browser:

<script src="node_modules/ljd-16-bit-cpu/cpu16bit.js"></script>
<script>
    var cpu = new ljd.cpu16bit.CPU();
</script>

From node.js:

var cpu16bit = require('ljd-16-bit-cpu');
var cpu = new cpu16bit.CPU();

Run a program

// rom is a array of 16-bit integers and length <= 65,536
cpu.loadProgram(rom);
cpu.run();

Step through a program

// Optionally, the ram contents may also be provided
// ram is a array of 16-bit integers and length <= 65,536
cpu.loadProgram(rom, ram);
cpu.step();
cpu.step();
// ...

Example program in hex

// This program adds the values in ram[0] and ram[1]
// then stores the result in ram[2]
// 27 + 73 = 100

var rom = [
  0x100A,       // HBY 0x00 RA
  0x200A,       // LBY 0x00 RA
  0x3A01,       // LOD RA R1
  0x201A,       // LBY 0x01 RA
  0x3A02,       // LOD RA R2
  0x5123,       // ADD R1 R2 R3
  0x202A,       // LBY 0x02 RA
  0x4A30,       // STR RA R3
  0x0000        // END
];

var ram = [27, 73, 0];
cpu.loadProgram(rom, ram);
cpu.run();
cpu.ram[2];     // returns 100

Developing

git clone [e-mail]:lj-ditrapani/16-bit-computer-cpu-coffeescript.git
cd 16-bit-computer-cpu-coffeescript
npm run build

This produces cpu16bit.js.

Lint and run tests on node with:

npm run all

Open run-specs.html in a browser to run the tests in a browser environment.

Author: Lyall Jonathan Di Trapani