ljd-16-bit-cpu

LJD 16-bit processor
====================

For other implementations, see .

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
-----------

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

Usage
-----

From browser:

``html

`

From node.js:

`js
const { makeCpu, makeDebugCpu } = require('ljd-16-bit-cpu')
// do stuff
`

Run a program

`js
// 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

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

Example program in hex

`js
// 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
-----------------


Developing
----------

$3

`bash
npm run all
`

This produces lib/ljd_16_bit_cpu.js for node environment and browser/ljd_16_bit_cpu.js
for browser environments respectively.

$3

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

`bash
npm run browser-test
`

Then open in your browser.
Open the developer console to see the 100.

`bash
firefox localhost:8000/manual-test.html
`

$3

Run manual test on node; prints 100.

`bash
node manual-test.js
``

$3

npm run ncu

$3

npm login
npm version patch/minor/major
npm publish

Author: Lyall Jonathan Di Trapani