To provide a serial interface circuit that can respond to the change in the data transmission system of the peripheral devices.

It has a serial interface circuit 10 in an ASIC (integrated semiconductor circuit) 1, and this interface circuit has the interface sections 11, 12, 13, and 14 each different in the number of control signals and in the serial data transmission systems. It switches the value of the set signal S outputted from the register 15 by changing the setting of the register 15 in the serial interface circuit 10 by using the data from the outside, and switches the data transmission system by making effective one of the interfaces 11, 12, 13, and 14.