Other

Control Systems, Inc.

Tallgrass Technologies Corporation

David M Allen

A read channel circuit includes a high frequency filter and a pair of differentiators, one of which is a high resolution differentiator and the other of which is a low resolution differentiator intentionally adjusted to perform its differentiation function imperfectly. Comparators serve as zero crossing detectors for the high and low resoltuion signals. The comparator for the low resoltuion path provides the data input to a flip-flop. The comparator for the high resolution path has its output processed by an exclusive OR gate and a delay circuit before being applied to the clock input of the flip-flop. The high-resolution and low-resolution paths are combined in the flip-flop, whose digital output faithfully reproduces the binary information received by the read head by deriving timing from the high-resoltuion path and by effectively discriminating against artifacts in the read head's signal which would result in spurious transitions in the read channel's output were it not for the imperfect differentiation provided in the low-resolution path.

Read channel architecture for processing read head signals

Digitally encoded information is stored on a data track in an improved format characterized by a leader field followed by a data field and a trash gap at the end of the data field. On a rotatable disk storage medium, the leader field has a randomly selected starting point which may change each time a new set of data is recorded on the track. The leader field contains encoded control information which signals the beginning of the ensuring data field. The trash gap may contain spurious data remaining from a previously recorded set of data and is maintained shorter than the leader field at all permissible rotational speeds of the disk to prevent spurious data on the trash gap from being erroneously recognized as valid leader field control information.

Format for storing data on magnetic media

A method and apparatus for implementing the same are provided for digitally synchronizing the timing of a sequence of electrical output pulses in accordance with a selectable, permissably non-linear function of the timing of a sequence of electrical input pulses. The method and apparatus are illustrated with reference to application thereof to overcoming the problem of degradation of synchronization caused by so-called 'peak shift' due to the adjacent data effect in the reading of binary data stored on magnetic disks or the like. Pulses of a timing reference signal having a uniform interval equal to a sub-multiple of the normal average interval of the desired output pulses are continuously counted to a number base equal to the denominator of said sub-multiple, and output pulses are produced whenever a pre-selected count value occurs. Output pulse timing correction values in accordance with the synchronizing function selected are stored in memory. A parameter of the input pulse sequence representing the occurrence of a new pulse therein is sensed and triggers substitution for the then existing count of the correction value accessed from memory at the address represented by the count existing prior to such substitution. Accurate synchronization of the timing of the output pulses with the actual, leading or lagging occurrence of input pulses is thereby accomplished on a continuing basis whenever a new input pulse produces the mentioned triggering, even with input pulse sequences from which only irregularly occurring, magnetic state transition boundaries may be sensed.

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Overland Park, KS, United States of America

David M Allen