Semiconductor device having calibration circuit that adjusts an impedance of output buffer and data processing system including the same

摘要

A calibration operation can be performed automatically at a semiconductor device without issuing a calibration command from a controller. Because a calibration operation is performed in response to a fact that the auto refresh command has been issued for a predetermined number of times, a periodical calibration operation can be secured and a read operation or a write operation is not requested from a controller during a calibration operation.