Method and apparatus for detecting a reference pattern in a transmitted
bit sequence. A duration of a search window used to detect the reference
pattern is adaptively adjusted in relation to a previous detection of the
pattern. This is preferably carried out by using a first search window to
initially detect the pattern, and then adjusting the first search window
to provide a second search window to subsequently detect the pattern.
Preferably, the search window is an elapsed period of time during which a
transducer is swept adjacent a storage medium to detect the reference
pattern. Servo data are preferably written as a sequence of adjacent
spiral servo patterns, and the reference pattern is preferably detected
each time to determine the relative location of the most recently written
spiral. Preferably, a larger search window is used for initial spirals
and a smaller search window is used for subsequently written spirals.