code: function() {
  		return (
  			( (!!this.pulse1.lengthCounter) << 0 ) |
  			( (!!this.pulse2.lengthCounter) << 1 ) |
  			( (!!this.triangle.lengthCounter) << 2 ) |
  			( (!!this.noise.lengthCounter) << 3 ) |
  			( (!!this.dmc.sampleBytesLeft) << 4 )
  		);
  	}
docs: Read channel status.