PURPOSE: To simplify a data converting circuit, by utilizing a dynamic type circuit which performs information refreshment at a low-speed operation at an interface for transmitting and receiving for the serial data.

CONSTITUTION: At the transmission side of a serial interface, parallel data are written in a transmit data register TDS and set in a register TSR for shifting in parallel. The refreshing and shifting operations of information is performed by a circuit loop composed of the TSR and shifter SH. In the case of serial transmission of a low-speed rate, for example, the SH performes 1-bit shifting operation only when a shift clock for transmission arrives and, at the other timing, the SH makes the information refreshment of a dynamic type circuit by performing the through operation. Therefore, serial pulse sending at a low- speed rate can be performed.