The present invention is directed to adjust a resistance value of an output buffer on the basis of a resistance value of an external resistor. A potential according to a resistance ratio between an external resistor and each of resistance adjusters is detected by a code generator. In the code generator, code signals for adjusting resistance are adjusted in accordance with the detection result. The resistance value of each of the resistance adjusters is adjusted to an external resistor. Further, by code signals with which the resistance value of each of the resistance adjusters is adjusted to the resistance value of the external resistor, the resistance of the resistance value of an output buffer is adjusted.