PURPOSE: To increase data transfer speed by transferring prepared identification code, data transfer amount and data in this order, controlling the transferred data in the order received in a reception circuit and a transmission/reception circuit, processing the received data to transfer it to an output device and transferring the data.

CONSTITUTION: The identification code showing the kind and form of data is prepared in an identification preparation circuit 33 and data transfer amount to be transferred at one time is prepared in a data transfer amount control circuit 33. The transferring direction of data is decided according to the kind and form of data, a transmission and reception circuit 27 is switched to be used bi-directionally according to the transfer direction of data in a transfer data direction switch circuit 34 and data is instructed to be trasferred by being distributed to a transmission and reception circuit 37 in a transmission circuit 36 by a data control circuit 35. By transferring the data transferred on a bit serial interface by using two bit serial interfaces, the performance of a data transfer is improved up to about double.