hdl-js/dist/emulator/hardware/builtin-gates/PC.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');

var _require = require('../../../util/numbers'),
    int16Table = _require.int16Table,
    int16 = _require.int16;

/**
 * Canonical truth table for the `PC` gate.
 */


var TRUTH_TABLE = int16Table([{ $clock: -0, in: 0, load: 0, inc: 0, reset: 0, out: 0 },

// PC = 5
{ $clock: +0, in: 5, load: 1, inc: 0, reset: 0, out: 0 }, { $clock: -1, in: 5, load: 1, inc: 0, reset: 0, out: 5 },

// PC++
{ $clock: +1, in: 5, load: 0, inc: 1, reset: 0, out: 5 }, { $clock: -2, in: 5, load: 0, inc: 1, reset: 0, out: 6 },

// PC++
{ $clock: +2, in: 6, load: 0, inc: 1, reset: 0, out: 6 }, { $clock: -3, in: 6, load: 0, inc: 1, reset: 0, out: 7 },

// Reset (PC = 0)
{ $clock: +3, in: 6, load: 0, inc: 0, reset: 1, out: 6 }, { $clock: -4, in: 6, load: 0, inc: 0, reset: 1, out: 0 },

// Preserve
{ $clock: +4, in: 0, load: 0, inc: 0, reset: 0, out: 0 }, { $clock: -5, in: 0, load: 0, inc: 0, reset: 0, out: 0 }]);

/**
 * A 16-bit counter with load and reset controls.
 *
 * out[t+1] = 0,          when reset[t] = 1
 * out[t+1] = in[t],      when load[t] = 1
 * out[t+1] = out[t] + 1, when inc[t] = 1 (default counting behavior)
 * out[t+1] = out[t],     otherwise (preserves as a register)
 *
 * Abstract:
 *
 *   IN in[16], load, inc, reset;
 *   OUT out[16];
 *
 *   Inc16(in=t0, out=t1);
 *   Mux16(a=t0, b=t1, sel=inc, out=t2);
 *   ...
 *   Register(in=t4, load=true, out=t0, out=out);
 */

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

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

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

  _createClass(PC, [{
    key: 'init',
    value: function init() {
      /**
       * The 16-bit value of the PC register.
       */
      this._value = 0;
    }

    /**
     * On rising edge PC register updates the internal
     * value according to the logic.
     */

  }, {
    key: 'clockUp',
    value: function clockUp() {
      var _in = this.getInputPins()[0].getValue();
      var load = this.getInputPins()[1].getValue();
      var inc = this.getInputPins()[2].getValue();
      var reset = this.getInputPins()[3].getValue();

      if (reset === 1) {
        this._value = 0;
      } else if (load === 1) {
        this._value = int16(_in);
      } else if (inc === 1) {
        this._value++;
      }
    }

    /**
     * On the falling edge PC register propagates
     * the value to the output pin.
     */

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

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

  return PC;
}(BuiltInGate);

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


PC.Spec = {
  name: 'PC',

  description: '\nA 16-bit counter with load and reset controls.\n\nout[t+1] = 0,          when reset[t] = 1\nout[t+1] = in[t],      when load[t] = 1\nout[t+1] = out[t] + 1, when inc[t] = 1 (default counting behavior)\nout[t+1] = out[t],     otherwise, preserves the value\n\nClock rising edge PC updates the value from the input,\nif the `load` is set; otherwise, preserves the state.\n\n  ' + colors.bold('↗') + ' : value = in, when ' + colors.bold('load') + '\n               0, when ' + colors.bold('reset') + '\n              +1, when ' + colors.bold('inc') + '\n\nClock falling edge PC propagates the value to the output:\n\n  ' + colors.bold('↘') + ' : out = value\n',

  inputPins: [
  // 16-bit value.
  { name: 'in', size: 16 },

  // Control bits.
  { name: 'load', size: 1 }, { name: 'inc', size: 1 }, { name: 'reset', size: 1 }],
  outputPins: [{ name: 'out', size: 16 }],

  truthTable: TRUTH_TABLE
};

module.exports = PC;