An information processing system includes a host and a storage device that transmits a first pulse signal to the host and receives a second pulse signal from the host through a transmission line. The storage device has a first register to store a value of a first parameter and correction circuit to adjust a first duty ratio of the first pulse signal according to the value of the first parameter. The host includes a first calibration processor that measures a plurality of the first duty ratios as output from the storage device for different values of the first parameter to derive a first optimum value based on the measured first duty ratios and transmit the derived first optimum value to the storage device as the value of the first parameter to be stored in the first register.