Semiconductor device, portable communication terminal, ic card, and microcomputer

Abstract

The present invention provides a noncontact interface technique capable of performing communication operation without stopping an internal operation even when a clock signal cannot be extracted from a carrier wave. In a semiconductor device that receives a modulated carrier wave from an antenna, generates an internal clock signal on the basis of a clock signal extracted from the received carrier wave, and performs operation synchronously with the internal clock signal, a PLL circuit that receives the extracted clock signal and generates the internal clock signal is provided with a voltage control oscillation function. In the case where the clock signal extracted from the carrier wave is discretely interrupted, the function makes the internal clock signal maintained at a frequency immediately before the interruption. With the configuration, even when the clock signal extracted from the carrier wave is interrupted, internal data processes such as decoding and bus interfacing can be continued.