US Patent 10038545 Systems and methods for clock and data recovery

A clock and data recovery (CDR) circuit includes a phase detector, a frequency accumulator, and a sequencer circuit. The phase detector generates a phase detect result signal in response to phase detection of a plurality of samples, which are generated by sampling a first data signal from a receiver using a sampling clock. The frequency accumulator accumulates, using a frequency register, frequency offset information from the phase detect result signal to generate an accumulated total. The frequency offset information is associated with a frequency difference between a first reference clock of the receiver and a second reference clock associated with the first data signal. The accumulated total is stored in the frequency register and provided from the frequency register for updating the sampling clock. The sequencer circuit is configured to perform a reset operation to reset the accumulated total in the frequency register based on a sequence of sequence elements.