To reduce the cost and to increase the operation speed, by carrying serial data from a serial data source to the data input terminal of a serial data processor through a bus and carrying an address signal, a control signal, and data to and from the serial data processor through another bus.

The data communication interface 10 is equipped with digital systems 12 and 14 and the bus 18 carries the address signal, control signal, and data to the serial data processor(SDP) 16 from the digital system 12. Similarly, an SDP 20 is interconnected to the digital system 14 by the data bus 22. The serial data source 24 applies a serial sequence of data to be written to the SDP 16 through the bus 26 and stores the data in the SDP 16 or in the SDP 20 through the SDP 16 and a bus 32. Further, a sequence of the serial data is stored in a serial data destination circuit 42 from a serial data output terminal 36 through a data bus 38.