Method and apparatus for aligning a clock signal and a data strobe signal in a memory system

Abstract

A method of aligning a clock signal and a data strobe signal in a system comprising a memory controller and a memory, and a corresponding memory system are provided. The method comprising the steps of: putting the memory into a write levelling mode; incrementing an alignment delay applied to the data strobe signal until a transition point occurs at which a response of the memory to issuance of the data strobe signal transitions to an inverse state; performing an oversampling of the response of the memory over a selected interval following said transition point; repeating the steps of incrementing and performing an oversampling until, for a selected alignment delay, a majority of results of the oversampling is in the inverse state; performing a cycle alignment detection procedure to determine an identified clock cycle of a plurality of adjacent cycles of the clock signal, the identified clock cycle responsible for the transition point; and applying the selected alignment delay to the data strobe signal and applying a clock cycle selection to a data path in the system to match the identified clock cycle.