US3800280A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Time skew measurement circuit for mag tape transports
Assignee: AG Communication Systems Corp
•
Filing: 1972-11-06
•
Granted: 1974-03-26
•
Expires: 1992-11-06
Abstract
Abstract A skew measurement circuit for determining the skew characteristics (i.e., the minimum, maximum and average skew) of a magnetic tape transport system is disclosed. The circuit includes an instantaneous skew counter for measuring the difference in arrival times at a tape head (i.e., instantaneous skew) between reference channel and test channel bits aligned in lateral registry across the tape to form informational bytes. An average skew counter comprising up/down decade counters is provided to total the instantaneous skew during a one million byte skew test so that the average skew may be determined by shifting the decimal point. The instantaneous skew is also coupled to a min/max comparison and storage arrangement where it is compared with previously stored minimum and maximum skew values, replacing the appropriate one in a storage register if it is found to be a new extreme. Because an atypical minimum or maximum may be stored due to conditions (e.g., tape binding, etc.) that are not characteristic of the transport system, a decrementing circuit is provided for decreasing the maximum stored value and increasing the minimum stored value at a predetermined rate. Accordingly, the legitimacy of the stored skew values may be insured by requiring that they be periodically refreshed.
Inventors
- 👤 S Heffner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 15:47
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/20
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
158 words
A circuit for monitoring the arrival of corresponding reference and test channel bits comprising an informational character (byte) at a tape head to determine the skew characteristics of a tape transport system; said skew measurement circuit comprising in combination: instantaneous counting means for measuring the instantaneous skew between the detected arrival of said reference bit at said tape head and the detected arrival of said corresponding test bit at said tape head; min/max comparison and storage means for detecting and storing the minimum and maximum values of said instantaneous skew, said min/max means subsequently comparing each said instantaneous skew with said stored values and replacing the appropriate one whenever new said maximums and minimum are detected; and decrementing means for decreasing said maximum stored value and increasing said minimum stored value at a predetermined rate so that said maximum and minimum stored values must be periodically refreshed to insure their validity as characteristic of said tape transport system.
Claim 2
Dependent Claim
158 words
A circuit for monitoring the arrival of corresponding reference and test channel bits comprising an informational character (byte) at a tape head to determine the skew characteristics of a tape transport system; said skew measurement circuit comprising in combination: instantaneous counting means for measuring the instantaneous skew between the detected arrival of said reference bit at said tape head and the detected arrival of said corresponding test bit at said tape head; min/max comparison and storage means for detecting and storing the minimum and maximum values of said instantaneous skew, said min/max means subsequently comparing each said instantaneous skew with said stored values and replacing the appropriate one whenever new said maximums and minimum are detected; and decrementing means for decreasing said maximum stored value and increasing said minimum stored value at a predetermined rate so that said maximum and minimum stored values must be periodically refreshed to insure their validity as characteristic of said tape transport system.
Claim 3
Dependent Claim
69 words
A skew measurement circuit in accordance with claim 1 including lead-lag decisioN means having reference channel and test channel inputs for determining which one of said reference and test bits in each of said characters is initially detected by said tape head, said lead-lag means developing an instantaneous skew sign signal indicating when said reference bit leads said test bit and when said reference bit lags said test bit.
Claim 4
Dependent Claim
95 words
A skew measurement circuit in accordance with claim 2 wherein said lead-lag decision means generates a lead signal during the time interval between the arrival of said reference bit at said tape head and the subsequent arrival of said corresponding test bit, said lead-lag means generating a lag signal during the time interval between the detection of said bits if said reference bit is detected subsequent to the arrival of said test bit, said instantaneous counting means being enabled to count only during the time interval when said lead and lag signals are applied thereto.
Claim 5
Dependent Claim
62 words
A skew measurement circuit in accordance with claim 3 including clock means for developing a clock pulse train having a predetermined frequency, said clock pulse train being applied to said instantaneous counting means for initiating a count therein coincident with each said clock during intervals when the appropriate one of said lead and lag signals is applied to said instantaneous counting means.
Claim 6
Dependent Claim
88 words
A skew measurement circuit in accordance with claim 2 including averaging means responsive to said instantaneous counting means for determining the average value of said instantaneous skew during said skew test, said averaging means totaling said instantaneous skew during a skew test comprising a plurality of said characters and developing an average skew sign signal indicating whether the total of said time intervals during which said reference bit leads said test bit exceeds the total of said time intervals during which said reference bit lags said test bit.
Claim 7
Dependent Claim
59 words
A skew measurement circuit in accordance with claim 5 wherein said averaging means includes counting means for adding said instantaneous skew to said total instantaneous skew if said instantaneous and average skew signs are the same, said counting means counting down to subtract said instantaneous skew from said total skew if said instantaneous and average skew sign are opposite.
Claim 8
Dependent Claim
58 words
A skew measurement circuit in accordance with claim 6 wherein said skew test comprises 10n characters and n in a positive integer, said averaging means totaling said instantaneous skew during said skew test to determine the average value of said instantaneous skew when decimal point associated with said total instantaneous skew is moved n places to the left.
Claim 9
Dependent Claim
17 words
A skew measurement circuit in accordance with claim 7 wherein said skew test comprises one million characters.
Claim 10
Dependent Claim
46 words
A skew measurement circuit in accordance with claim 2 wherein said lead-lag decision means includes means for arbitrarily designating said instantaneous skew sign to be positive when said reference bit leads said test bit and to be negative when said reference bit lags said test bit.
Claim 11
Dependent Claim
120 words
A skew measurement circuit in accordance with claim 9 wherein said min/max comparision and storage means comprise minimum and maximum storage register means for storing the minimum and maximum values of said instantaneous skew, said min/max means further including minimum and maximum comparator means for generating a load max signal and a load min signal, said load max signal being coupled to said maximum storage register means to replace said maximum stored value in said maximum register means with said instantaneous skew whenever said instantaneous skew exceeds said maximum stored value, said load min signal being coupled to said minimum storage register means to replace said minimum stored value when said instantaneous skew is less than said minimum stored value.
Claim 12
Dependent Claim
154 words
A skew measurement circuit in accordance with claim 10 wherein said maximum comparator means include magnitude comparator means and sign comparator means, said sign comparator means comparing the sign of said instantaneous skew with the sign of said maximum stored value and generating said load max signal if said instantaneous skew sign is positive and the sign of said maximum stored value is negative, said magnitude comparator means comparing the absolute values of said instantaneous skew and said maximum stored value to determine if the absolute value of said instantaneous skew is greater than said maximum stored value, said sign comparator means also generating said load max when both of said signs are positive and the magnitude of said instantaneous skew is greater than that of said maximum stored value and when both of said signs are negative and the magnitude of said instantaneous skew is less than that of said maximum stored value.
Claim 13
Dependent Claim
152 words
A skew measurement circuit in accordance with claim 10 wherein said minimum comparator means include magnitude comparator means and sign comparator means, said sign comparator means comparing said instantaneous skew sign with the sign of said stored minimum value and generating load min signal if said instantaneous skew sign is negative and the sign of said minimum stored value is positive, said magnitude comparator means comparing the absolute values of said instantaneous skew and said minimum stored value to determine if the absolute value of said instantaneous skew is less than said minimum stored value, said sign comparator means also generating said load min signal when both of said signs are negative and the magnitude of said instantaneous skew is greater than that of said minimum stored value and when both of said signs are positive and the magnitude of said instantaneous skew is less than that of said minimum stored value.
Claim 14
Dependent Claim
36 words
A skew measurement circuit in accordance with claim 10 wherein said load max and load min signals are simultaneously generated to load the initial value of said instantaneous skew into said maximum and minimum storage registers.
Claim 15
Dependent Claim
60 words
A skew measurement circuit in accordance with claim 10 wherein both said minimum and maximum storage register means comprise synchronous up/down decade counters coupled to said instantaneous counting means, said instantaneous skew being loaded into said maximum up/down counters whenever said load max signal is applied thereto and into said minimum up/down counters whenever said load min signal is generated.
Claim 16
Dependent Claim
80 words
A skew measurement circuit in accordance with claim 14 wherein said decrementing means generates a decrement signal occurring at a predetermined frequency, each said decrement signal initiating a corresponding down count by said maximum up/down decade counters if said maximum stored value is positive and an up count if said maximum stored value is negative, said decrement signal initiating down count by said minimum up/down decade counters if said minimum stored value is negative and an up count if positive.
Claim 17
Dependent Claim
39 words
A skew measurement circuit in accordance with claim 15 wherein said decrementing means includes a unijunction transistor relaxation oscillator for determining the frequency at which said decrement signals are generated, said relaxation oscillator being adjustable to vary said frequency.
Claim 18
Dependent Claim
46 words
A skew measurement circuit in accordance with claim 1 including control means for generating internal control signals so that said instantaneous counting means, said min/max comparision and storage means and said decrementing means are sequentially enabled, said control means including reference channel and test channel inputs.
Claim 19
Dependent Claim
71 words
A skew measurement circuit in accordance with claim 17 including character gate means having reference channel and test channel inputs for generating a character gate signal coincidentally with the detection of the first one of said bits, said character gate signal continuing for a predetermined time interval during which the other of said bits can also be detected, said character gate signal being coupled to an input of said control means.
Claim 20
Dependent Claim
83 words
A skew measurement circuit in acCordance with claim 18 wherein said control means generate a first control signal during the interval that said character gate signal is generated, said first control signal being coupled to said instantaneous counting means enabling it to measure said instantaneous skew, said first control signal further being applied to said min/max comparison and storage means enabling comparison of said instantaneous skew with said minimum stored value and said maximum stored value after said instantaneous skew has been determined.
Claim 21
Dependent Claim
65 words
A skew measurement circuit in accordance with claim 18 wherein said control means generates a first error signal whenever at least two of said reference bits are detected during said character gate interval, said error signal also being generated if at least two of said test bits are detected during said character gate interval, said error signal being effective to reset said instantaneous counting means.
Claim 22
Dependent Claim
49 words
A skew measurement circuit in accordance with claim 18 wherein said control means generates a second error signal if said character gate interval ends before said reference bit is detected, said second error signal also being generated if said character gate interval ends before said test bit is detected.
Claim 23
Dependent Claim
41 words
A skew measurement circuit in accordance with claim 18 wherein said control means generates a second control signal when both of said bits have been detected and said character gate signal has ended, said second control signal enabling said decrementing means.
Claim 24
Dependent Claim
41 words
A skew measurement circuit in accordance with claim 18 wherein display means are included for providing a visual read-out of the results of said skew test, said display means being driven by and coupled to said min/max comparision and storage means.
Claim 25
Dependent Claim
34 words
A skew measurement circuit in accordance with claim 23 wherein said display means further comprises means for displaying said maximum stored value and said minimum stored value upon the completion of said skew test.
Claim 26
Dependent Claim
65 words
A skew measurement circuit in accordance with claim 23 including byte counter means having an input coupled to said character gate signal for generating a skew stop signal coupled to said control means and wherein said control means generates a third control signal when said skew test is complete, said third control signal enabling said display means to display the results of said skew test.
Claim 27
Dependent Claim
56 words
A skew measurement circuit in accordance with claim 25 including byte counting means for counting said character gate signals, said byte counting means enabling said control means to continue said skew test as long as the number of said character gate signals counted by said byte counting means indicates that said skew has not been completed.
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) | 1977-03-25 | 1977-09-24 | 1978-03-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-25 | 1981-09-24 | 1982-03-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-25 | 1985-09-24 | 1986-03-26 | $7700.00 | Window Closed / Lapsed |