CLOCK GENENRATION CIRCUIT CAPABLE OF CHANGING FREQUENCY

摘要

A clock generating circuit capable of frequency change is provided to improve the security function of a smart card by variously changing the frequency of a clock signal. A random number generator(115) generates a random number consisting of a plurality of bits. The first comparison circuit(113) delivers bits of the first group of the random number to an output stage. A counter(112) outputs a count value by being synchronized with an external clock. The second comparator circuit(118) outputs the bits of the first group of the random number outputted from the first comparison circuit as a frequency control signal. A clock generator generates a clock signal having a frequency corresponding to the frequency control signal.