nes-emu/apu/frameClock.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
const QUARTERS_4_STEP = [3729, 7457, 11186, 14916];
const QUARTERS_5_STEP = [3729, 7457, 11186, 18641];

/** The NES APU frame counter (or frame sequencer) generates low-frequency clocks for the channels. */
var _default = exports.default = {
  measure(frameClockCounter, use5StepSequencer, onIRQ, onQuarter, onHalf, onEnd) {
    const quarters = use5StepSequencer ? QUARTERS_5_STEP : QUARTERS_4_STEP;
    const isQuarter = frameClockCounter === quarters[0] || frameClockCounter === quarters[1] || frameClockCounter === quarters[2] || frameClockCounter === quarters[3];
    const isHalf = frameClockCounter === quarters[1] || frameClockCounter === quarters[3];
    const isEnd = frameClockCounter === quarters[3];
    if (isQuarter) onQuarter();
    if (isHalf) onHalf();
    if (isEnd) {
      onEnd();
      if (!use5StepSequencer) onIRQ("frame");
    }
  }
};