code: function _readFC4(data, next) {
      var length = data.readUInt8(2);
      var contents = [];
  
      for (var i = 0; i < length; i += 2) {
          var reg = data.readUInt16BE(i + 3);
          contents.push(reg);
      }
  
      if (next)
          next(null, { "data": contents, "buffer": data.slice(3, 3 + length) });
  }
docs: Parse the data for a Modbus -
  Read Input Registers (FC=04, 03)
  
  @param {Buffer} data the data buffer to parse.
  @param {Function} next the function to call next.