The data transfer has room for improvement of reduction in the operating electric current flowing on the signal bus and correct acquisition of the large amount of data. Each of data, a first clock signal and a second clock signal, a phase of which shifts by a predetermined amount from the first clock signal, has an amplitude that is smaller than an amplitude of a power supply voltage, and each of a semiconductor device and a memory device takes input of data in synchronization with rise edges of first and second clock signals.