Clock data recovery circuit and method

Abstract

A change-point detection circuitextracts a clock signal from serial data, input data. A variable delay circuit provides a delay in accordance with a delay control signal to a reference signal having a predetermined frequency, so that the phase of the reference signal is shifted on the basis of an initial delay. An input latch circuit latches internal serial data by using an output signal of the variable delay circuit as a strobe signal. A phase comparator matches the frequencies of the clock signal and the strobe signal with each other, and generates phase difference data in accordance with a phase difference between the two signals. A loop filter integrates the phase difference data generated by the phase comparator and outputs it as the delay control signal. The phase shift amount acquisition unit acquires a phase shift amount based on the delay control signal, the phase shift amount being based on the initial delay provided to the reference signal by the variable delay circuit.