Patent ID: 7818469

Claim:
A Universal Serial Bus (USB) device comprising a plurality of functional modules that includes a control circuit for switching a functional module to be activated from among the functional modules comprised in the USB device according to a potential level of a power supplied from a USB host connected to the USB device, wherein the control circuit comprises: a discrimination circuit for discriminating a voltage value of the power; a control circuit for controlling powers to be applied to the functional modules; a memory circuit for storing a descriptor indicating a type and a characteristic of the USB device; and a plurality of data structure analyzing units corresponding to the type of the USB device, wherein the control circuit turns a functional module to be activated from among the functional modules, which the USB device comprises, into an ON state according to a type of the USB device corresponding to a discrimination result of the voltage value of the power by the discrimination circuit, thereby transferring the descriptor indicating the type and the characteristic of the USB device corresponding to the discrimination result to the USB host, and wherein the data structure analyzing unit corresponding to the type and the characteristic of the USB device indicated by the descriptor analyzes data transmitted in accordance with the descriptor from the USB host and processes data to be transmitted to the USB host so that the data corresponds to the type and the characteristic of the USB device indicated by the descriptor.