hdl-js/dist/emulator/hardware/builtin-gates/Bit.js

Hardware definition language (HDL) and Hardware simulator

/**
 * The MIT License (MIT)
 * Copyright (c) 2017-present Dmitry Soshnikov <dmitry.soshnikov@gmail.com>
 */

'use strict';

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

var colors = require('colors');
var BuiltInGate = require('../BuiltInGate');

/**
 * Canonical truth table for the `Bit` gate.
 */
var TRUTH_TABLE = [{ $clock: -0, in: 0, load: 0, out: 0 }, { $clock: +0, in: 1, load: 1, out: 0 }, { $clock: -1, in: 1, load: 0, out: 1 }, { $clock: +1, in: 1, load: 0, out: 1 }, { $clock: -2, in: 1, load: 0, out: 1 }, { $clock: +2, in: 0, load: 1, out: 1 }, { $clock: -3, in: 0, load: 0, out: 0 }];

/**
 * 1 bit memory register.
 * If load[t]=1 then out[t+1] = in[t] else out does not change.
 *
 * Abstract:
 *
 *   IN in, load;
 *   OUT out;
 *
 *   Mux(a=t0, b=in, sel=load, out=t1);
 *   DFF(in=t1, out=t0, out=out);
 */

var Bit = function (_BuiltInGate) {
  _inherits(Bit, _BuiltInGate);

  function Bit() {
    _classCallCheck(this, Bit);

    return _possibleConstructorReturn(this, (Bit.__proto__ || Object.getPrototypeOf(Bit)).apply(this, arguments));
  }

  _createClass(Bit, [{
    key: 'init',
    value: function init() {
      /**
       * The state (0/1) of the bit.
       */
      this._state = 0;
    }

    /**
     * On rising edge Bit updates the internal state
     * if the `load` is set, otherwise -- preserves the state.
     */

  }, {
    key: 'clockUp',
    value: function clockUp() {
      var load = this.getInputPins()[1].getValue();

      if (load) {
        this._state = this.getInputPins()[0].getValue();
      }
    }

    /**
     * On the falling edge Bit propagates the state
     * to the output pin.
     */

  }, {
    key: 'clockDown',
    value: function clockDown() {
      this.getOutputPins()[0].setValue(this._state);
    }
  }], [{
    key: 'isClocked',

    /**
     * Bit is a sequential gate.
     */
    value: function isClocked() {
      return true;
    }
  }]);

  return Bit;
}(BuiltInGate);

/**
 * Specification of the `Bit` gate.
 */


Bit.Spec = {
  name: 'Bit',

  description: ['1 bit memory register.', '', 'If load[t]=1 then out[t+1] = in[t] else out does not change.', '', 'Clock rising edge updates internal state from the input,', 'if the `load` is set; otherwise, preserves the state.', '', '  ' + colors.bold('↗') + ' : state = load ? in : state', '', 'Clock falling edge propagates the internal state to the output:', '', '  ' + colors.bold('↘') + ' : out = state'].join('\n'),

  inputPins: ['in', 'load'],
  outputPins: ['out'],

  truthTable: TRUTH_TABLE
};

module.exports = Bit;