US3761905A
Expired / Lapsed
US
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Disc pack defect detection system
Assignee: Information Storage Systems Inc
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Filing: 1971-08-20
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Granted: 1973-09-25
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Expires: 1991-08-20
Abstract
Abstract A method and system are described for detecting defective surface areas in magnetic recording discs. Detection is effected during initialization of a disc pack before data is recorded thereon for storage, therby permitting defective areas to be subsequently avoided during data storage. The method includes the steps of producing a reference signal from the readback signal derived from a recording disc during initialization thereof, and of comparing the contemporaneous or instantaneous value of the readback signal with the value of the reference signal to detect any abrupt reduction in the value of the readback signal. The duration of any such reduction is measured, and whenever it exceeds a predetermined time period, a defect signal is developed which interrupts the initialization process and is used to prevent later use of the defective area represented by the abrupt reduction. The system includes amplification, rectification, timing, and output circuits which process the readback signals and produce the defect signals in the manner described. It further includes a peak hold circuit and voltage divider for producing a reference signal based on the peak value of the readback signals but reduced to a fixed percentage thereof. A comparator circuit continuously compares such reference signal with the value of the contemporaneous readback signal for the purpose of detecting any such abrupt reduction in the latter to a value below that of the reference signal.
Inventors
- 👤 C Hollstein
- 👤 R Cloke
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 06:22
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; G11B20/18; G01; G01R; G01R33/00; G01R33/12; G01R33/1207; G06; G06F; G06F11/00; G06F11/22; G06F11/24
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
172 words
In a method for detecting defective areas in the recording surface of data storage devices during initialization thereof to permit such areas to be avoided for data storage, the steps of producing a readback signal from said recording surface, producing a reference signal of predetermined value by processing said readback signal to provide a threshold based upon a percentage of the maximum value of said readback signal, comparing the value of the readback signal with the value of said reference signal to detect any abrupt reduction in tHe value of the readback signal, measuring the duration of any such abrupt reduction in the value of the readback signal, and in response to the presence of a value reduction having a duration in excess of a predetermined interval and a magnitude less than said threshold, producing a defect signal operative to interrupt the initialization process and prevent data recording at the defective area represented by the abrupt reduction in the value of the readback signal during use of the surface for data storage.
Claim 2
Dependent Claim
172 words
In a method for detecting defective areas in the recording surface of data storage devices during initialization thereof to permit such areas to be avoided for data storage, the steps of producing a readback signal from said recording surface, producing a reference signal of predetermined value by processing said readback signal to provide a threshold based upon a percentage of the maximum value of said readback signal, comparing the value of the readback signal with the value of said reference signal to detect any abrupt reduction in tHe value of the readback signal, measuring the duration of any such abrupt reduction in the value of the readback signal, and in response to the presence of a value reduction having a duration in excess of a predetermined interval and a magnitude less than said threshold, producing a defect signal operative to interrupt the initialization process and prevent data recording at the defective area represented by the abrupt reduction in the value of the readback signal during use of the surface for data storage.
Claim 3
Dependent Claim
194 words
In a method for detecting defective areas in the recording surface of data storage devices during initialization thereof to permit such areas to be avoided for data storage, the steps of producing a readback signal from said recording surface, producing a reference signal of predetermined value by processing said readback signal by developing an intermediate signal corresponding to the peak value of the readback signal over a number of cycles thereof, and reducing the value of such intermediate signal to a fixed percentage of such peak value of the readback signal to produce said reference signal, comparing the value of the readback signal with the value of said reference signal to detect any abrupt reduction in the value of the readback signal, measuring the duration of any such abrupt reduction in the value of the readback signal, and in response to the presence of a value reduction having a duration in excess of a predetermined interval, producing a defect signal operative to interrupt the initialization process and prevent data recording at the defective area represented by the abrupt reduction in the value of the readback signal during use of the surface for data storage.
Claim 4
Dependent Claim
194 words
In a method for detecting defective areas in the recording surface of data storage devices during initialization thereof to permit such areas to be avoided for data storage, the steps of producing a readback signal from said recording surface, producing a reference signal of predetermined value by processing said readback signal by developing an intermediate signal corresponding to the peak value of the readback signal over a number of cycles thereof, and reducing the value of such intermediate signal to a fixed percentage of such peak value of the readback signal to produce said reference signal, comparing the value of the readback signal with the value of said reference signal to detect any abrupt reduction in the value of the readback signal, measuring the duration of any such abrupt reduction in the value of the readback signal, and in response to the presence of a value reduction having a duration in excess of a predetermined interval, producing a defect signal operative to interrupt the initialization process and prevent data recording at the defective area represented by the abrupt reduction in the value of the readback signal during use of the surface for data storage.
Claim 5
Dependent Claim
48 words
The method of claim 1 in which the readback signal from such data storage device is continuously processed, said reference signal being the product of a plurality of successive cycles of the readback signal whereas the contemporaneous value compared therewith is comprised of a limited number of cycles.
Claim 6
Dependent Claim
45 words
The method of claim 1 in which said readback signal is an alternating current signal, and including the further step of converting the readback signal into a unipolar signal prior to producing said reference signal and the value of the readback signal for comparison therewith.
Claim 7
Dependent Claim
45 words
The method of claim 4 in which said readback signal includes representations of both clock and data pulses, and in which the step of converting the readback signal to unipolar includes combining the representations of the clock and data pulses into a composite unipolar signal.
Claim 8
Dependent Claim
107 words
The method of claim 5 in which the step of processing the readback signal to produce a reference signal therefrom includes developing an intermediate signal corresponding to the peak value of the readback signal over a number of cycles thereof, and reducing the value of such intermediate signal to a fixed percentage of such peak value of the readback signal to produce said reference signal, and in which the readback signal from such surface is continuously processed, said reference signal being the product of a plurality of successive cycles of the readback signal whereas the contemporaneous value compared therewith is comprised of a limited number of cycles.
Claim 9
Dependent Claim
202 words
In combination with a random access memory device having a readback network, a defect detection system for locating defective areas in a data recording surface during initialization thereof to permit such areas to be avoided for data storage, comprising: means for producing a reference signal of a predetermined value to provide a threshold based upon a percentage of the maximum value of said readback signal, a comparator circuit for comparing such reference signal with the value of the readback signal to detect any abrupt reduction in the value of the readback signal, a timing circuit connected with said comparator circuit and operative to measure the duration of any such abrupt reduction in the value of the readback signal, and an output circuit connected with said timing circuIt and operative in response to the presence of a value reduction measured thereby having a duration in excess of a predetermined interval and a magnitude less than said threshold to produce a defect signal and transmit the same to said readback network to interrupt the initialization process and prevent data recording at the defective area represented by the abrupt reduction in the value of the readback signal during use of the surface for data storage.
Claim 10
Dependent Claim
202 words
In combination with a random access memory device having a readback network, a defect detection system for locating defective areas in a data recording surface during initialization thereof to permit such areas to be avoided for data storage, comprising: means for producing a reference signal of a predetermined value to provide a threshold based upon a percentage of the maximum value of said readback signal, a comparator circuit for comparing such reference signal with the value of the readback signal to detect any abrupt reduction in the value of the readback signal, a timing circuit connected with said comparator circuit and operative to measure the duration of any such abrupt reduction in the value of the readback signal, and an output circuit connected with said timing circuIt and operative in response to the presence of a value reduction measured thereby having a duration in excess of a predetermined interval and a magnitude less than said threshold to produce a defect signal and transmit the same to said readback network to interrupt the initialization process and prevent data recording at the defective area represented by the abrupt reduction in the value of the readback signal during use of the surface for data storage.
Claim 11
Dependent Claim
66 words
The combination of claim 7 in which said means for producing a reference signal includes a peak hold circuit comprising a capacitance storage network provided with a relatively long discharge time constant, the capacitance storage network being charged by the peak value of the readback signal pulses delivered thereto, and the reference signal being based on the value to which said capacitance storage circuit is charged.
Claim 12
Dependent Claim
50 words
The combination of claim 8 in which said means for producing a reference signal further includes a voltage divider preceding the input to said comparator circuit to reduce the value of the reference signal to a predetermined percentage of the peak value to which said capacitance storage network is charged.
Claim 13
Dependent Claim
126 words
The combination of claim 7 in which said means for producing a reference signal further includes a gated amplifier connected with said readback network so as to receive therefrom signals representative of both the clock and data pulses comprising the readback signal, and a full-wave rectifier connected with said gated amplifier so as to receive therefrom amplified replicas of said signals representative of the clock and data pulses, said rectifier being operative to produce a composite output signal from said representative signals and deliver the same to said peak hold circuit, said amplifier being adapted to have enabling signals delivered thereto to change the condition thereof from an inoperative, high impedance input condition to an operative state to process the readback signals from said readback network.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-24 | 1977-03-26 | 1977-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-24 | 1981-03-26 | 1981-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-24 | 1985-03-26 | 1985-09-25 | $7700.00 | Window Closed / Lapsed |