US Patent 7889581 Digital DLL circuit

A digital delay locked loop circuit generates a delay value to delay the timing of taking in read-data by a memory interface when data is read from a memory. The digital delay locked loop circuit includes a selector that selects either one of a clock signal and a data strobe signal as a signal to output; a delay line that induces delay on the signal output from the selector when the signal passes through the delay line; and a phase-comparing/delay-value determining unit that compares a phase of the clock signal and a phase of the signal output from the delay line, and that determines a delay value that defines an amount of delay to be induced on the data strobe signal when passing through the delay line.