US Patent 9379880 Clock recovery circuit

Clock data recovery can be accomplished using a phase change determination circuit that generates, based upon detected phase differences between a capture clock signal and data signal, a delta signal and a delta selection signal. A calculation circuit generates a set of phase interpolation (PI) codes from prior and speculative values of the delta signal. A selection circuit selects, in response to the delta selection signal, between the sets of PI codes, which are provided as an output of the clock data recovery device.