Patent ID: 7131021
Filing Date: 2006-10-31
Classification: H03K,H03L,H04L

Abstract:
1. An apparatus for automatic delay calibration of a forward clock, comprising: control logic for receiving a normal clock, a lead clock and a lag clock, and generating a delay control signal based on a timing relationship among the normal clock, the lead clock and the lag clock; and a delay calibrator for receiving a reference clock having the same frequency as the forward clock to provide the normal, the lead and the lag clocks as feedback to the control logic, and adjusting the lead and the lag clocks in accordance with the delay control signal; wherein the delay control signal is provided to perform a delay calibration for the forward clock once the timing relationship has been adjusted to meet a predetermined condition; and wherein the control logic includes a state transition table having a set of present states, a set of prior states, a set of prior actions and a set of next actions, each of the present states being defined by a currently received timing relationship among the normal, the lead and the lag clocks, each of the prior states being defined by a previously received timing relationship among the normal, the lead and the lag clocks, each of the prior actions being indicative of a prior adjustment for the delay control signal, and each of the next actions being indicative of a next adjustment for the delay control signal.