code: public boolean maskWriteRegister(int ref, int andMask, int orMask) throws ModbusException {
          return maskWriteRegister(DEFAULT_UNIT_ID, ref, andMask, orMask);
      }
docs: Mask write a single register to the slave.
  
  @param ref       the offset of the register to start writing to.
  @param andMask   AND mask.
  @param orMask    OR mask.
  
  @return true if success, i.e. response data equals to request data, false otherwise.
  
  @throws ModbusException if an I/O error, a slave exception or
  a transaction error occurs.