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 Program memory addresses (16-bit resolution)
• 2^16 = 65,536 Data memory addresses (16-bit resolution)
• Program & data memory are word-addressable
• A word is 16 bits (2 bytes)
• All instructions are 16 bits long
• 16 instructions (4-bit op-code)

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

npm package

https://www.npmjs.com/package/ljd-16-bit-cpu

npm install --save ljd-16-bit-cpu

Usage

From browser:

<script type="module">
import { makeCpu, makeDebugCpu } from "/lib/ljd_16_bit_cpu.js"
// do stuff
</script>

From node.js:

import { makeCpu, makeDebugCpu } from 'ljd-16-bit-cpu'
// do stuff

Run a program

// programRom is a array of 16-bit integers with length <= 65,536
const cpuWithIoRam = makeCpu(programRom, dataRom)
const cpu = cpuWithIoRam.cpu
const ioRam = cpu.run(1000)

Step through a program

const cpuWithIoRam = makeDebugCpu(programRom, dataRom)
const cpu = cpuWithIoRam.cpu
cpu.step()
cpu.step()
// ...

Example program in hex

// This program adds the values in dataRom[0] and dataRom[1]
// then stores the result in ioRam[512]
// 27 + 73 = 100
// Address $FA00 is the beginning of screen RAM == ioRam[512]

const programRom = [
  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
  0x1FAA,       // HBY 0xFA RA
  0x200A,       // LBY 0x00 RA
  0x4A30,       // STR RA R3
  0x0000        // END
]

const dataRom = [27, 73, 0]
const cpuWithIoRam = makeCpu(programRom, dataRom)
const cpu = cpuWithIoRam.cpu
const ioRam = cpu.run(1000)
console.log(ioRam[512])      // prints 100

API Documentation

https://lj-ditrapani.github.io/16-bit-cpu-ts/

Developing

Setup

Install node with https://github.com/nvm-sh/nvm.

nvm install     # one-time install
nvm use         # each time you enter the project directory

Install npm packages.

npm install

Format, lint, test, build

npm run all

This produces a single ljd_16_bit_cpu.js esm module for both node and browser environments.

Test coverage

# Run the tests with `npm run all` or
npm test
# This will generate the test coverage report
# Then open the test coverage report
firefox coverage/lcov-report/index.html

Manual browser test

Run manual test in browser; prints 100 to dev console.

npm run browser-test

Then open localhost:8000/manual-test.html in your browser. Open the developer console to see the 100.

firefox localhost:8000/manual-test.html

Manual node test

Run manual test on node; prints 100.

node manual-test.js

Generate documentation

npm run doc
firefox docs/index.html &

Update dependencies

npm run ncu

Publish

rm -fr lib
npm run all
npm version patch/minor/major
npm login
npm publish

Author: Lyall Jonathan Di Trapani