In view of accurately determine a valid range of data to be synchronized to the system clock, conforming to actual environments of mounting and connection, the semiconductor device of the present invention is configured as acquiring flight times of clock signal(s) and a data strobe signal, transmitted to or from a double-data-rate memory, making use of reflected waves on transmission path, and as determining a valid range of data to be synchronized with a system clock based on thus-acquired flight times of the clock signal(s) and the data strobe signal.