broken-neees/apu/FrequencySweep.js

A really broken NEEES emulator that introduces glitches and random bugs on purpose!

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
const APU_MIN_TIMER = 8;
const APU_MAX_TIMER = 0x7ff;
class FrequencySweep {
  constructor(channel) {
    this.channel = channel;

    // input
    this.startFlag = false;

    // output
    this.dividerCount = 0;
    this.mute = false;
  }
  clock() {
    const register = this.channel.registers.sweep;
    if (register.enabledFlag && register.shiftCount > 0 && this.dividerCount === 0 && !this.mute) {
      const sweepDelta = this.channel.timer >> register.shiftCount;
      this.channel.timer += sweepDelta * (register.negateFlag ? -1 : 1);
    }
    if (this.dividerCount === 0 || this.startFlag) {
      this.dividerCount = register.dividerPeriodMinusOne + 1;
      this.startFlag = false;
    } else this.dividerCount--;
  }
  muteIfNeeded() {
    this.mute = this.channel.timer < APU_MIN_TIMER || this.channel.timer > APU_MAX_TIMER;
  }
}
exports.default = FrequencySweep;