The PD72001-11 is an MPSC (Multi-Protocol Serial Controller) which is a general-purpose communication LSI equipped with two sets of bidirectional parallel/serial converter circuits for data communication. This controller has a transmitter function to convert the parallel data output by a data terminal into serial data and transmit this data to a data transmission system such as a modem, and a receiver function to convert the serial data output by the data transmission system into parallel data. The MPSC can be used with data communications equipment with a variety of communication modes such as the generally and widely used start-stop synchronization mode, and the HDLC mode which is used for high-speed communication.