nes-emu/cartridge/mappers/_0_NROM.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _Mapper = _interopRequireDefault(require("./Mapper"));
var _memory = require("../../memory");
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
/**
 * The simplest mapper (also called "mapper 0").
 * It can have either one or two PRG ROM of 16KB, that are mapped
 * at ranges $8000-$BFFF and $C000-$FFFF of the CPU memory.
 * It also has CHR ROM which contains the tile and sprite data.
 * This CHR ROM is mapped to the PPU memory at addresses $0000-$1FFF.
 */
class NROM extends _Mapper.default {
  static get id() {
    return 0;
  }

  /** Creates a memory segment for CPU range $4020-$FFFF. */
  createCPUSegment(_ref) {
    let {
      cartridge
    } = _ref;
    const unused = new _memory.MemoryPadding(0x3fe0);
    const prgRomFirstPage = this._newPrgBank();
    const prgRomLastPage = cartridge.header.prgRomPages === 2 ? this._newPrgBank(1) : new _memory.MemoryMirror(prgRomFirstPage, 0x4000);
    return _memory.WithCompositeMemory.createSegment([
    //                  Address range   Size      Description
    unused,
    //          $4020-$7FFF     $3FE0     Unused space
    prgRomFirstPage,
    // $8000-$BFFF     $4000     PRG ROM (first 16KB of ROM)
    prgRomLastPage //   $C000-$FFFF     $4000     PRG ROM (second 16KB of ROM or mirror)
    ]);
  }

  /** Creates a memory segment for PPU range $0000-$1FFF. */
  createPPUSegment(_ref2) {
    let {
      cartridge
    } = _ref2;
    return this._newChrBank(cartridge);
  }
}
exports.default = NROM;