Abstract: An amplitude detector incorporated in an electronic device with a serial ATA interface detects the amplitude of a serial data signal input to an I/O circuit via a SATA bus. An averaging unit averages the detection results of the amplitude detector. A comparator compares the resultant average with an expected input signal amplitude. Based on the comparison result, an amplitude adjuster adjusts the amplitude of a serial data signal when this signal is output from the I/O circuit. Adjustment is performed such that when the serial data signal output from the I/O circuit is input to another electronic device via the SATA bus, it has an amplitude at least approximately equal to the expected input signal amplitude. In other embodiments, the invention utilizes an amplitude detector, comparator and adjuster and employs a step-by-step adjustment of the electronic device with another similarly equipped electronic device.