AU602197B2 - Creation of Inventions and Patents with Artificial Intelligence

AU602197B2 – Disc memory servo indexing system
– Google Patents

AU602197B2 – Disc memory servo indexing system
– Google Patents
Disc memory servo indexing system

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Publication number
AU602197B2

AU602197B2
AU13153/88A
AU1315388A
AU602197B2
AU 602197 B2
AU602197 B2
AU 602197B2
AU 13153/88 A
AU13153/88 A
AU 13153/88A
AU 1315388 A
AU1315388 A
AU 1315388A
AU 602197 B2
AU602197 B2
AU 602197B2
Authority
AU
Australia
Prior art keywords
sync
pulse
track
pulses
frames
Prior art date
1987-03-30
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Withdrawn – After Issue

Application number
AU13153/88A
Other versions

AU1315388A
(en

Inventor
David J. Bezinque
James O. Jacques
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Seagate Technology LLC

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Seagate Technology LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1987-03-30
Filing date
1988-03-16
Publication date
1990-10-04

1988-03-16
Application filed by Seagate Technology LLC
filed
Critical
Seagate Technology LLC

1988-09-29
Publication of AU1315388A
publication
Critical
patent/AU1315388A/en

1990-10-04
Application granted
granted
Critical

1990-10-04
Publication of AU602197B2
publication
Critical
patent/AU602197B2/en

2008-03-16
Anticipated expiration
legal-status
Critical

Status
Withdrawn – After Issue
legal-status
Critical
Current

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Classifications

G—PHYSICS

G11—INFORMATION STORAGE

G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER

G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor

G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed

G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following

G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks

G11B5/59605—Circuits

G11B5/59616—Synchronisation; Clocking

G—PHYSICS

G11—INFORMATION STORAGE

G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER

G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor

G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed

G11B5/59633—Servo formatting

Description

V
C_0KN C.H VA L T O0F AU0S T RALI A PATENT ACT 1952 COMPLETE SPECI FICATION A~c 19 i
(ORIGINAL)
FOR OFFICE USE CLASS INT. CLASS Application Number: Lodged: Complete Specif ication Lodged: Accepted: Published: Priority: This document contains the L an,dments made under Section 49 and is cjrrect for printing.
Related Art-: NAME OF APPLICANT: ADDRESS OF APPLICANT: (I SEAGATE TECHNOLOGY, INC., 920 Disc Drive, Scotts Valley, California 95066 United States-of America NAME(S) OF INVENTOR(S) David Joseph BEZINQUE James Oliver JACQUES DAVIES COLLISWXl. Patent Attorneys 1 Little Collins Street, Melbourne. 3000.
ADDRESS FOR SERVICE: 4*~ COMPLETE SPECIFICATION FORi THE INVENTION ENITTLED: “DISC MEMORY SERVO INDEXING SYSTEM” fbe following statement Is a faill descrdption of this Imvetionv Including the best method of pledfoziulg~it known to us
-I-
Vq 89 to This invention relates generally to magnetic disk 0 o memory systems, and more particularly the invention **0 I relates to a servo indexing system in a magnetic disc 004 5 memory.
The magnetic disc memory includes a plurality of discs mounted on a common spindle in spaced, parallel ‘9relationship. Data is magnetically recorded in 0′ magnetic coatings on the surfaces of the discs in 98 a aa0 10 concentric tracks. The data is recorded and accessed :too by pickup heads which move across the disc surfaces 9″ as the discs are rotated.
TyPically, one surface of the disc surfaces is dedicated to servo control for the pickup heads.
15 Data is recorded in the plurality of tracks which allow a dedicated servo control pickup head to identify Guard Bands at the inner and outer limits of the data tracks a data Track Zero, and all other data trackcs. Additionally, pulses are provided to permit accurEte alignment of the pickup heads in each track.
The data in each track is arranged in frames.
Typically, a first plurality of pulses in each frame are utilized to identify the status of the track and a second plurality of pulses are utili~ed for pickup
T
2 if r t
IL
(r
P
L E i 18 19 f 21 22 23 24 25 26 27 28 29 31 32 33 34 36 37 head alignment. For example, the IBM 3350 disc drive utilizes two sync pulses at the beginning of each frame for encoding a bit of data and utilizes four additional pulses (Sig and Quad) for track alignment. The presence or ahsence of one of the two sync pulses determines the data bit as a or a U.S. Patent No. 4,495,533 discloses a similar arrangement but reverses the order of sync pulses in encoding data allegedly for overcoming a problem of erroneous data readout when the rotational speed of the discs varies. The system also utilizes a crystal clock oscillator for circuit synchronization and control. The patent recognizes a problem of oscillator control when rotational speed varies, and the patent discloses a circuit for delaying selected clock pulses to maintain synchronization of the pulses with data being read from the servo track.
An object of the present invention is an improved servo indexing system.
Another object of the invention is a servo indexing system which does not require a crystal clock oscillator for timing and synchronization.
According to the invention there is provided a servo disc in a magnetic disc drive comprising a plurality of data tracks and Guard Bands, each track and Guard Band including a plurality of frames, each frame including first and second sync pulse groups of at least one sync pulse each, a first track alignment signal (Quad) following said first sync group, and a second track alignment signal (Sig) following said second sync group.
The invention also provides a method of identifying Guard Band tracks and a data Track Zero in a disc surface comprising the steps of: providing magnetic pulses in a plurality of frames and 6 90072gcpdat.O27,I3153c, 2 22 1 each track on said disc surface, said magnetic pulses in 2 each frame including first and second sync pulse groups of I3 at least one sync pulse each a first track alignment signal 4 (Quad) following said first sync group, and a second track alignment signal (Sig) following said second sync group, and 6 selectively eliminating sync pulses in a plurality of 7 frames in each track.
8 9 The invention also provides in a magnetic disc drive including a servo disc surface having magnetic pulses 11 arranged in a plurality of frames in concentric tracks, each 12 frame including first and second sync pulse groups of at 13 least one sync pulse each, circuitry responsive to said sync 14 pulses for generating signals identifying a track comprising: 16 a first monostable one-shot multivibrator for 17 generating a pulse in response to a sync pulse, 18 charging circuitry means responsive to a plurality of 19 sync pulses in one group to generate a trigger signal, means connecting said first monostable one-shot 21 irtultivibrator to said charging circuit means, 22 a first flip-flop circuit connected to said charging 23 cir’cuit means and responsive to said trigger signal for 24 generating a f.’rst output signal, first logic gate means responsive to the presence of 26 said output for generating a Sig gate pulse, and 27 means responsive to periodic occurrence of said Sig 28 gate pulse to identify a track.
29 Briefly, two groups of on~e or more sync pulses are provided 31 in each frame in the servo tracks which cause the generation 32 of track alignment gate signals (Quad and Sig). Inhibiting 33 generation of either the Quad or Sig gates once in a 34 predetermined number of 36 k900723, gcpdat.027,13153c,3 -3frames identifies the Guard Rands, Track Zero, and all other data tracks.
In a preferred embodiment, each frame includes a first sync pulse which causes generation of a Quad gate pulse, and second and third sync pulses which together cause generation of a Sig gate pulse.
Absence of either of the second and third sync pulses inhibits generation of the Sig gate pulse. A Guard Band is identified by the absence of the Sig gate pulse once in every ten frames, and the Track Zero is identified by the absence of the Sig gate pulse once in every thirty frames. he identification of the track by the absence of Sig gate pulses is accomplished by timing circuitry in the form of gates, flip-flops, and one-shot multivibrators.
The invention and objects and features thereof will be more readily apparent with the following detailed description and appended claims when taken with the drawings, in which: FIG. 1 is a perspective view illustrating a magnetic disc drive.
FIG. 2 is an illustration of servo signals in accordance with prior art.
FIGS. 3A and 3B illustrate servo signals in accordance with one embodiment of the present invention.
FIG. 4 is a schematic of circuitry responsive to the servo signals of Figs. 3A and 3B for identifying’ a U 0 r 3 i I^–XYIILP~C Il–l–Xl o0 0 Co 00 0 0 0 0 oa o o 0 0 o a0 0 04 0 t0 oo a 0 0 0 *0 -4track index, a Guard Band, a Track Zero, and all other data tracks.
FIGS. 5A and 5B, 5C and 5D illustrate the sequences of Sig gate pulses which identify Guard Band, Track Zero, and all other data tracks, respectively.
Referring now to the drawing, Figure 1 is a perspective view illustrating a portion of a magnetic disc drive. The disc drive includes a plurality of discs 10 with the surfaces of the discs 10 having 10 magnetic coatings for the recording of bits of data, and The bits of data are recorded on the surfaces in concentric tracks with the data grouped in frames of data words. The bits of data are recorded and accessed by means of magnetic heads 15 12 which are driven across the surfaces of the discs 10 by means of a carriage assembly 14 as the discs are rotated.
As described above, one surface of one disc is typically dedicated to servo control of the carriage assembly and positioning of the pickup heads 12.
Magnetic pulses are recorded in the frames of the tracks on the servo surface so that the location of the pickup head a Guard Band or data track can be identified and also for proper positioning of the pickup head within a data track. As shown in Figure 2, the pulse format of the IBM 3350, for example, includes two sync pulses Si and S2, followed by four position pulses W1 W4 in each frame. The presence or absence of the first sync pulse, Si, encodes a bit of data with the bits of a plurality of sequential frames defining the Guard Band, Track Zero, or other data tracks. U.S. Patent No.
4,495,533, supra, utilizes a similar pattern but
T
-7 utilizes the presence or absence of the second sync pullse, S2, for recording a data bit. The patent also teaches the use of a crystal controlled oscillator for timing in accessing the track position bits Wl- W4 following the reception of the sync bits.
According to the patent, this can lead to pulse identification problems when the oscillator is not synchronized with the rotational speed of discs.
In accordance with the present invention, a unique bit pattern is employed which can be accessed by unique circuitry without the requirement for a crystal controlled oscillator. The circuitry employs monostable one-shot multivibrators, flip-flops, and logic gates to identify a track index, Guard Band, and data tracks. As shown in Figure 3A the index frame at the beginning of each track is 22 segments long and includes a first sync pulse Sl followed by a Quad pulse, and four sequential sync pulses S2 which are followed by a Sig pulse. The Quad and Sig pulses are utilized for head alignment within each track. All other frames on the servo disc surface have a pattern as illustrated in Figure 3B. Again, a first sync pulse Sl is followed by a Quad pulse, and then two sync pulses 52,53 are followed by the Sig pulse. Circuitry is provided which responds to the sync pulses for generating gating signals at the proper time following the sync pulses for sampling the Quad and Sig pulses recorded on the servo disc surface. Additionally, the circuitcy recognizes the four sequential sync pulses S2 S5 in the index frame and also recognizes a Guard Band, track 0 and other data tracks by the presence of the two sync pulses S2,S3 or the absence of either of the two sync pulses S2,S3 as shown in Figure 3B.
4q44 iI 1
I
-6- Figure 4 is a schematic diagram of one embodiment of the circuitry which responds to the sync pulses for generating Quad and Sig gate signals and also for generating index, Track Zero, and Guard Band detect signals. The detected sync pulses are applied to the B input of one-shot multivibrator 28 (4G) and also to the C inputs of the flip-flops 34 and 38 The one-shot output of multivibrator 28 (4G) passes through a charging .circuit shown generally at 30 with the output of the charging circuit 30 applied to inputs of differential amplifiers 32 and 36 (4F).
Output 1 of amplifier 32 (4F) is applied to the D O° I input of flip-flop 34 (5F) and the Q output of flipi o flop 34 (5F) is the index detect signal.
The output of charging circuit 30 is also applied to an input of differential amplifier 36 and the o o output 7 of amplifier 36 is connected to the D input i^ 0 0of flip-flop 38. The Q output of flip-flop 38 is o o 00 applied to one input of NAND gate 40 and the Q output of flip-flop 38 is applied to one input of NAND gate I 42 and NAND gate 44.
The second flip-flop 46 has the C input connected to the output of a NAND gate 48 and the Q output of flip-flop 46 is connected to an input of NAND gate 40. The output of NAND gate 40 is connected to one input of NAND gate 48, and the output of NAND gate 52 i is connected to the A input of one-shot multivibrator The Q output of multivibrator 50 is connected to the A input of multivibrator 28 and to the A.nputs of NAND gates 42 and 48, The output of NAND gate 42 is connected to one input of NAND gate 52 with the output of NAND gates 52 and 44 cross-coupled as indicated.
L
-7- A sig gate signal is derived at the output of NAND gate 48, and a quad gate signal is derived at the output of NAND gate 42. The Sig gate signal is connected to the input of a one-shot multivibrator having a pulse duration on the order of microseconds. The Q output of one-shot multivibrator is connected to the input of a second one-shot multivibrator 62 wnich has a pulse duration of 0 0 approximately 240 microseconds. The Q output of 0 a 4 10 multivibrator 60 is connected also to the C input of flip-flop 64 and to the C input of flip-flop 66. The o output of one-shot multivibrator 62 is connected to the D input of flip-flop 64, and the Q output of flip-flop 64 is connected to the D input of flip-flop 66. A Track Zero signal is derived at the output of o one-shot multivibrator 62 in response to the absence of one of the sync pulses S2,S3, once every thirty fyrames, and a Guard Band detect signal is obtained at 00 the Q output of flip-flop 66 in response to the 0 20 absence of the sync pulse S3 once every ten frames.
Presence of all three sync pulses Si, S2 and S3 for thirty frames indicates a data track other than Track 0 0 Zero.
Consider now the timing diagrams of Figures 5k-5C in conjunction with the circuitry of Figure 4. In Figure 5A, the presence of four sync pulses S2 in an index frame causes the output of flip-flop 34 (SFh) to toggle as indicated in response to the positive voltage level on the D input of flip-flop 34 when the sync pulse S5 is applied to the C input of flip-flop 34. In the absence of the four sync pulses S2 S5, the Q output of flip-flop 34 (5F) remains at a positive voltage level.
Figure 5B illustrates the inhibiting of a Sig gatka pulse due to the absence of the S3 sync pulse in the format of Figure 3B. As noted, flip-flop 50 normally toggles in response to the two sync pulses S2, F3.
However, absence of sync pulse S3 results in no toggle of multivibrator 50 with the result that the Q output of flip-flop 38 remains igh. With the Q output of flip-flop 38 high, the Sig gate signal at the output of NAND gate is inhibited.
The Sig gate signal is monitored, and absence of the Sig gate signal once in ten fames indicates Guard Band and absence of the Sig gate signal once in thirty frames indicates a Track Zero as shown in Figures SC and SD. Presence of the Sig gate in all frames is indicative of all other data tracks. In Figure SC, the inhibited gate signal appears as a negative pulse which is applied to the flip-flop with the output of the flip-flop being a negative microsecond pulse as illustrated in Figure SC. The 240 microsecond Output of flip-flop 62 goes high and 4 remains high in response to the recurring negative pulses every ten frames. The positive output of inultivibrator 62 forces the output of flip-flop 64 to a high level, and the Q, output of 4lip-f lop 66 assumes a low level as an indication of Guard Band detect.
Referring to Figure SD, the absence of Sig gate pulse once in thirty frames allows multivibrator 62 to toggle since the 240 microsecond time perioid of multivibrator 62 is less than the 330 microsecond time period of the recurring negative Sig gate pulses. The toggling of mUltivibrator 62 is detected.
as a Track Zero signal.
-9- The detection of the unique servo patterns by means of circuitry employing monostable one-shot multivibrators, flip-flops, and gating circuitry, in accordance with the invention, improves the accuracy and reliability of pulse detection in the servo pattern. Synchronization of an oscillator circuit with the rotational speed of the magnetic discs is obviated. While the invention has been described SS'”t with reference to a specific embodiment, the 4 10 description is illustrative of the invention and is not to be construed as limiting the invention.
Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.
4 0 B h s 9

Claims (9)

1. A servo disc in a magnetic disc drive comprising a plurality of data tracks and Guard Bands, each track and Guard Band including a plurality of frames, each frame including first and second sync pulse groups of at least one sync pulse each, a first track alignment signal (Quad) fullowing said first sync group, and a second track alignment signal (Sig) following said second sync group.

2. The servo disc as defined by Claim 1 wherein >1 track identification is provided by selectively eliminating sync pulses in a plurality of frames.

3. The servo disc as defined by Claim 2 wherein a Guard Band Is identified by eliminating one sync pulse in every ten frames and a. data Track Zero is identif ied by eliminating one sync pulse in every thirty frames.

4. A method of identifying Guard Band tracks and a data Track Zero in a disc surface comprising the steps of: proviaing magnetio pulses in a plurality of frames and each track on said disc surface, said magnetic pulses in eac~h frame including first and second sync pulse groups of at least one sync pulse each, a first track alignment signal (Quad) following said first sync g’toup, and a second tack alignment signal (Sig) following said second sync group, and selectively eliminating sync pulses in a plurality of frames in each track.

5. The method as defined by Claim 4 wherein said step of selectively e13.ninating sync pulses includes -11- eliminating one sync pulse in every ten frames for identifying a Guard Band, and eliminating one sync pulse in every thirty frames to identify a data Track Zero.

6. In a magnetic disc drive including a servo disc surface having magnetic pulses arranged in a plurality of frames in concentric tracks, each frame L c\ ao including first and second sync pulse groups of at S, least one sync pulse each, circuitry responsive to S 10 said sync pulses for generating signals identifying a Strack comprising: *I 0 a first monostable one-shot multivibrator for 1 iT generating a pulse in response to a sync pulse, charging circuitry means responsive to a plurality of sync pulses in one group to generate a trigger signal, means connecting said first monostable one-shot multivibrator to said charging circuit means, a first flip-flop circuit connected to said charging circuit means and responsive to said trigger signal for generating a first output signal, osrr first logic gate means responsive to the presence of said output for generating a Sig gate pulse, and means responsive to periodic occurrence of said Sig gate pulse to identify a track. A*

7. Circuitry as defined by Claim 6 wherein said means responsive to periodic occurrence of said Sig gate pulse includes one-shot multivibrator circuitry responsive to omission of said Sig gate pulse once during a first time period to identify a Guard Band and responsive to omission of said Sig gate pulse during a second time period to indicate a Track Zero. 12

8. A servo disc in a magnetic disc drive substantially as hereinbefore described with reference to the accompanying drawings.

9. A method of identifying Guard Band Tracks and a data Track Zero in a disc surface substantially as hereinbefore described with reference to the accompanying drawings. re cr. c c i f 11 12 13 S* 14 c St 16 17 18 19 21 Si I S 22 23 24 4 26 27 28 29 31 32 33 34 DATED this 23rd day of July, 1990 SEAGATE TECHNOLOGY, INC. By its Patent Attorneys DAVIES COLLISON d 900723 gqcpdat.027 ,13163c, 12

AU13153/88A
1987-03-30
1988-03-16
Disc memory servo indexing system

Withdrawn – After Issue

AU602197B2
(en)

Applications Claiming Priority (2)

Application Number
Priority Date
Filing Date
Title

US3176487A

1987-03-30
1987-03-30

US031764

1987-03-30

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Publication Number
Publication Date

AU1315388A

AU1315388A
(en)

1988-09-29

AU602197B2
true

AU602197B2
(en)

1990-10-04

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Title
Priority Date
Filing Date

AU13153/88A
Withdrawn – After Issue

AU602197B2
(en)

1987-03-30
1988-03-16
Disc memory servo indexing system

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(1)

EP0285283A3
(en)

AU
(1)

AU602197B2
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CA
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CA1320270C
(en)

Citations (1)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

AU499654B2
(en)

1975-07-24
1979-04-26

International Business Machines Corp.

Data storage apparatus

Family Cites Families (4)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

US4390910A
(en)

1981-01-30
1983-06-28
Ball Corporation
Phase-lock oscillator

US4418368A
(en)

1981-03-31
1983-11-29
Disctron, Inc.
Method and apparatus for positioning a transducer using embedded servo track encoding

US4495533A
(en)

1982-06-28
1985-01-22
Atasi Corporation
Disk memory indexing system

US4616275A
(en)

1984-10-22
1986-10-07
Priam Corporation
Disc servo with 1F-2F servo pattern

1988

1988-03-15
EP
EP88302245A
patent/EP0285283A3/en
not_active
Withdrawn

1988-03-16
AU
AU13153/88A
patent/AU602197B2/en
not_active
Withdrawn – After Issue

1988-03-29
CA
CA000562731A
patent/CA1320270C/en
not_active
Expired – Fee Related

Patent Citations (1)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

AU499654B2
(en)

1975-07-24
1979-04-26
International Business Machines Corp.
Data storage apparatus

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Publication date

AU1315388A
(en)

1988-09-29

EP0285283A3
(en)

1989-11-29

CA1320270C
(en)

1993-07-13

EP0285283A2
(en)

1988-10-05

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