static isControlCode(b1) {
    // For control codes, the first byte takes the following form:
    // b1 -> |P|0|0|1|X|X|X|X|
    return (b1 & 0x70) === 0x10;
  }
Checks if the data contains a control code.
@param {number} b1 Byte 1.
@return {boolean}