In a CPU, a FET is turned off and power is not supplied to a power supply element of a transceiver for a period of time until predetermined initialization processing, which is implemented in a peripheral device when power is supplied via a cable from a host PC, has been concluded (i.e., a period of time until it becomes possible for the peripheral device to initiate data communication with the host PC). Thus, even if the peripheral device and the host PC are physically connected by a cable, data signals transmitted along signal lines are not relayed by the transceiver to a logic controller, whereby it in effect becomes possible to set the peripheral device in a pseudo-non-connected state with respect to the host PC.