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Abstract

A method and apparatus are described for controlling a phase of the data window, using data patterns in addition to any dedicated sync patterns to improve the synchronization when decoding data from a magnetic recording medium, such as, for example, a floppy diskette. A data window is generated to separate the data pulses from the clock pulses in a pulse series which has been recorded using a method which generates peak shifts such as MFM (Multi-Frequency Modulation) or FM. When a pulse series that matches any of a set of predetermined bit patterns is found in the data, the phase of the data window signal is adjusted based on the deviation of the timing of a selected transition in the pattern from the expected ideal value. Preferably the bit patterns have a plurality of symmetrically arranged bits and include a criterion position that is not affected by a peak shift. The pulse series from the recording medium is separated into data pulses and clock pulses by using the adjusted data window.

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First Claim