Phase lock loop

摘要

A phase lock loop includes a phase shift apparatus to provide a plurality (i.e., four) phase-shifted clock signals from the VCO. A phase selector is responsive to a triggering signal from a one-shot multivibrator to select the one phase-shifted clock signal next following termination of the trigger signal. The one-shot is responsive to a change between the read and write mode to initiate operation of the phase selector. As a result, the initial phase error between the input signal (read pulses or write clock) and the clock signal of the phase lock loop is no more than 1/8 window.