US3710358A
Expired / Lapsed
US
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Data storage system having skew compensation
Assignee: International Business Machines Corp
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Filing: 1970-12-28
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Granted: 1973-01-09
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Expires: 1990-12-28
Abstract
Abstract A data recording system is disclosed in which skew occurring between parallel data tracks is compensated for by an arrangement which measures the skew during a given field and adjusts the size of the immediately following gap by one half the measured skew. The disclosed system comprises a magnetic disk file of the fixed head type in which opposite pairs of magnetic heads are alternatively employed to transfer data to and from a logical track comprising one half the circumference of each of a pair of circular tracks on a magnetic disk. The skew of each field within a logical track is measured and one half the measured value is, depending on the type of system used, added to or subtracted from the nominal size of a gap between the previous field and the immediately following field. Skew compensation is implemented by a circuit which counts bit ring cycles between occurrence of the early track and the late track, divides the resulting count by two and stores the quotient until the end of the field, and adds the stored bits to constants for the gap before turning on a write driver to update the following field in the case of a write operation or before locking a variable frequency oscillator to the data to be read in the case of a read operation.
Inventors
- 👤 A Gindi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:25
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/20
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
120 words
In an arrangement in which plural transducers simultaneously address different respective ones of a plurality of nominally parallel tracks on a record member which undergoes motion relative to the transducers to perform read or write operations with respect to a succession of recordings extending along the nominally parallel tracks and separated by gaps of nominal length, an arrangement for compensating for skew between the nominally parallel tracks as presented to the associated transducers, comprising: means for sensing the skew present between the nominally parallel tracks within each of the recordings; and means responsive to the skew sensing means for changing the nominal length of the following gap by an amount corresponding to one half the value of the sensed skew.
Claim 2
Dependent Claim
120 words
In an arrangement in which plural transducers simultaneously address different respective ones of a plurality of nominally parallel tracks on a record member which undergoes motion relative to the transducers to perform read or write operations with respect to a succession of recordings extending along the nominally parallel tracks and separated by gaps of nominal length, an arrangement for compensating for skew between the nominally parallel tracks as presented to the associated transducers, comprising: means for sensing the skew present between the nominally parallel tracks within each of the recordings; and means responsive to the skew sensing means for changing the nominal length of the following gap by an amount corresponding to one half the value of the sensed skew.
Claim 3
Dependent Claim
39 words
An arrangement in accordance with claim 1, wherein the means for changing the nominal length comprises means for increasing the nominal length of the following gap by an amount equal to one half the value of the sensed skew.
Claim 4
Dependent Claim
39 words
An arrangement in accordance with claim 1, wherein the means for changing the nominal length comprises means for decreasing the nominal length of the following gap by an amount equal to one half the value of the sensed skew.
Claim 5
Dependent Claim
189 words
In an arrangement in which different ones of a plurality of pairs of transducing elements are selectively employed to perform read or write operations by simultaneously addressing a common pair of informational tracks which undergo motion relative to the transducing elements, an arrangement for compensating for skew which may occur between the individual tracks of the common pair such that one track is presented early and the other track is presented late relative to a given pair of the transducing elements, comprising: means coupled to the given pair of transducing elements for measuring skew between the individual tracks; means responsive to the skew measuring means for computing one half the measured skew; means coupled to the given pair of transducing elements and responsive to the termination of a deskew interval within the early track and to the computing means for commencing measurement of an interval of length equal to a nominal value plus one half the measured skew along the track; and means associated with the measurement commencing means and responsive to the end of the measured interval for simultaneously initiating a read or write operation in both tracks.
Claim 6
Dependent Claim
189 words
In an arrangement in which different ones of a plurality of pairs of transducing elements are selectively employed to perform read or write operations by simultaneously addressing a common pair of informational tracks which undergo motion relative to the transducing elements, an arrangement for compensating for skew which may occur between the individual tracks of the common pair such that one track is presented early and the other track is presented late relative to a given pair of the transducing elements, comprising: means coupled to the given pair of transducing elements for measuring skew between the individual tracks; means responsive to the skew measuring means for computing one half the measured skew; means coupled to the given pair of transducing elements and responsive to the termination of a deskew interval within the early track and to the computing means for commencing measurement of an interval of length equal to a nominal value plus one half the measured skew along the track; and means associated with the measurement commencing means and responsive to the end of the measured interval for simultaneously initiating a read or write operation in both tracks.
Claim 7
Dependent Claim
83 words
An arrangement in accordance with claim 4, wherein the means for measuring skew between the individual tracks comprises counter means, means responsive to the occurrence of a reference gap in the early track at the associated transducing element for initiating a count within the counter means and means responsive to the occurrence of a reference gap in the late track at the associated transducing element for terminating the count within the counter means, the count within the counter means comprising the measured skew.
Claim 8
Dependent Claim
139 words
A data storage system having increased storage capacity and incorporating a succession of fields extending along adjacent portions of parallel tracks of a record member and separated by gaps of nominal clock count value and a plurality of transducer elements associated with different ones of the parallel tracks, the relative locations of the transducer elements along the length of the parallel tracks being known only within predetermined tolerances, comprising: means coupled to the transducer elements for measuring skew between the adjacent portions of parallel tracks comprising at least some of the fields; means responsive to a selected fixed occurrence at the end of each field for starting clock count of the following gap; and means responsive to the measured skew for adjusting the value of the gap clock count by an amount equal to one half of the skew.
Claim 9
Dependent Claim
139 words
A data storage system having increased storage capacity and incorporating a succession of fields extending along adjacent portions of parallel tracks of a record member and separated by gaps of nominal clock count value and a plurality of transducer elements associated with different ones of the parallel tracks, the relative locations of the transducer elements along the length of the parallel tracks being known only within predetermined tolerances, comprising: means coupled to the transducer elements for measuring skew between the adjacent portions of parallel tracks comprising at least some of the fields; means responsive to a selected fixed occurrence at the end of each field for starting clock count of the following gap; and means responsive to the measured skew for adjusting the value of the gap clock count by an amount equal to one half of the skew.
Claim 10
Dependent Claim
46 words
The invention defined in claim 6 above, wherein each field comprises adjacent portions of two parallel tracks and the Means for measuring skew is coupled to a pair of the transducer elements, each of which is associated with a different one of the two parallel tracks.
Claim 11
Dependent Claim
44 words
The invention defined in claim 7 above, wherein two different pairs of the transducer elements are associated with the two parallel tracks and the skew between adjacent parallel track portions corresponds to the difference in orientation of the two different pairs of transducer elements.
Claim 12
Dependent Claim
195 words
A cyclic recording system for packing records of known length along parallel tracks of a cyclically driven record member with improved efficiency in data storage where a nominal record gap must be observed despite use of separate transducers along tracks that may be arbitrarily selected for read or write, said records including reference portions containing record gaps of selected nominal length, comprising: means including counter means responsive to movement of the record member for providing record gaps of the selected nominal size during writing; a pair of transducer means coupled to read from and record on paired tracks on the record member and responsive to said means for providing record gaps; detector means coupled to each of the transducer means and responsive to signals therefrom for sensing the relative displacement of each record on a time base; counter means coupled to said detector means for generating a count corresponding to the relative skew between the records on the paired tracks; and means responsive to said counter means and coupled to control said means providing record gaps for changing the selected nominal size of the gaps by one half the actual skew before reading or writing.
Claim 13
Dependent Claim
195 words
A cyclic recording system for packing records of known length along parallel tracks of a cyclically driven record member with improved efficiency in data storage where a nominal record gap must be observed despite use of separate transducers along tracks that may be arbitrarily selected for read or write, said records including reference portions containing record gaps of selected nominal length, comprising: means including counter means responsive to movement of the record member for providing record gaps of the selected nominal size during writing; a pair of transducer means coupled to read from and record on paired tracks on the record member and responsive to said means for providing record gaps; detector means coupled to each of the transducer means and responsive to signals therefrom for sensing the relative displacement of each record on a time base; counter means coupled to said detector means for generating a count corresponding to the relative skew between the records on the paired tracks; and means responsive to said counter means and coupled to control said means providing record gaps for changing the selected nominal size of the gaps by one half the actual skew before reading or writing.
Claim 14
Independent Claim
256 words
A system for the storage and retrieval of digital information comprising: a rotatable magnetic disk having a plurality of circular tracks disposed thereon, each adjacent pair of the tracks defining a succession of variable fields separated by gaps of nominal length; a plurality of groups of magnetic transducing heads, each group being generally disposed along a different common radius of the disk with each head thereof being in transducing relation to a different one of the tracks; central processing means for presenting digital information to be written on the disk and receiving digital information read from the disk and operative to provide command signals indicating operations to be performed on the disk; head select means responsive to the command signals from the central processing means and to the disk for selecting a pair of the heads from the head group closest to an field on the disk to be addressed; and means coupled between the central processing means and the pair of heads selected by the head select means for transferring digital information between the central processing means and the selected pair of heads during read and write operations in response to the command signals and including means for correcting skew between the tracks associated with the selected pair of heads, the skew correcting means including means for measuring the skew present at a given field, and means responsive to the measured skew for adjusting the nominal length of a gap immediately following the given field by an amount equal to one half the nominal skew.
Claim 15
Independent Claim
256 words
A system for the storage and retrieval of digital information comprising: a rotatable magnetic disk having a plurality of circular tracks disposed thereon, each adjacent pair of the tracks defining a succession of variable fields separated by gaps of nominal length; a plurality of groups of magnetic transducing heads, each group being generally disposed along a different common radius of the disk with each head thereof being in transducing relation to a different one of the tracks; central processing means for presenting digital information to be written on the disk and receiving digital information read from the disk and operative to provide command signals indicating operations to be performed on the disk; head select means responsive to the command signals from the central processing means and to the disk for selecting a pair of the heads from the head group closest to an field on the disk to be addressed; and means coupled between the central processing means and the pair of heads selected by the head select means for transferring digital information between the central processing means and the selected pair of heads during read and write operations in response to the command signals and including means for correcting skew between the tracks associated with the selected pair of heads, the skew correcting means including means for measuring the skew present at a given field, and means responsive to the measured skew for adjusting the nominal length of a gap immediately following the given field by an amount equal to one half the nominal skew.
Claim 16
Dependent Claim
196 words
A system in accordance with claim 10, wherein the means for transferring digital information includes first and second channels coupled between the central processing means and a different one of the selected pair of heads, each of the first and second channels including oscillator means operative to selectively lock to digital information read by the associated head for passing the information to the central processing means, and write driver means operative to pass digital information from the central processing means to the associated head for writing on the associated disk track when turned on, and wherein the means for adjusting the nominal length of a gap comprises means responsive to a fixed occurrence at the beginninG of the immediately following gap for counting to a value equal to the nominal length of the gap as adjusted by one half the measured skew, and means responsive to the end of the count for locking the oscillator means in the first and second channels to the digital information in the case of a following read operation and for turning on the write driver means in the first and second channels in the case of a following write operation.
Claim 17
Dependent Claim
87 words
A system in accordance with claim 11, wherein each field includes a sync gap within each of the two adjacent tracks, and wherein the means for measuring the skew comprises separate means within each of the first and second channels for detecting the occurrence of a sync gap therein, and counter means coupled to each of the sync gap detecting means and operative to count the time difference between occurrence of sync gaps in the first and second channels, the time difference count representing the measured skew.
Claim 18
Dependent Claim
59 words
A system in accordance with claim 12, wherein each of the first and second channels includes bit ring means coupled to cycle in response to each bit of digital information in the channel, and wherein the counter means is coupled to count cycles of the bit ring means between occurrence of sync gaps in the first and second channels.
Claim 19
Dependent Claim
77 words
A system in accordance with claim 13, further including separate buffer means within each of the first and second channels for temporarily storing digital information from the associated head, and buffer control means coupled to the buffer means in the first and second channels and responsive to the storage of a predetermined number of bits of the digital information in either buffer means for sequentially passing the corresponding bits of each channel to the central processing means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-01-09 | 1976-07-10 | 1977-01-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-09 | 1980-07-10 | 1981-01-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-09 | 1984-07-10 | 1985-01-09 | $7700.00 | Window Closed / Lapsed |