JP2004253042A - Disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a burst error rate due to synchronous shift by improving formatting efficiency in a disk unit such as a removable disk causing eccentricity. <P>SOLUTION: A servo-clock synchronized to disk rotation from time reference information recorded in servo-segments arranged at a substantially regular interval in a circumferential direction of a magnetic disk 1 is generated. In an RG pulse period indicating a reproduction processing period of a reproduction object data sector in a data segment, a reproduction clock component obtained by reproducing the data sector is transmitted to a PLL circuit 11 for data clock generation. Except for the RG pulse period, the servo-clock obtained through a frequency synthesizer PLL 6 from PLL 5 for servo-clock generation is transmitted to the PLL circuit 11 for the data clock generation. The data clock synchronized to each clock is generated. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

つまり、最低限必要なバイトシンク検出窓長Ｌｓｙｎｃ＿ａｃｔに加えて、偏心マージンとして、
２ΔＬｒｇ＿ｓｔａｒｔ＋２ΔＬｗｇ＿ｓｔａｒｔ
の長さのバイトシンク検出窓を必要とする。
【００５８】
ところが、バイトシンク検出窓を拡大することにより、次のような弊害が発生する。すなわち、シンクバイト検出動作時間が拡大することにより、シンクバイト直後より始まるユーザデータをシンクバイトと誤って検出することにより、シンクバイト誤検出確率が増大する可能性がある。また、シンクバイト誤検出時には検出タイミングが最大２ΔＬｒｇ＿ｓｔａｒｔ＋２ΔＬｗｇ＿ｓｔａｒｔだけ遅れるため、当該データセクタに続く次のデータセクタにまでＲＧパルスが重なることがあり、これによる悪影響（例えば、次のセクタのデータ読み込みの失敗）を防ぐため、データセクタ間のギャップにマージンを加える必要がある。
【００５９】
このデータセクタ間のギャップにマージンを加える点について、図１１を参照しながら説明する。図１１の（ａ）は、偏心なしの場合のセクタ間ギャップｇｐのみを設けた従来フォーマットを示し、このフォーマットのデータセクタＤ_ｎのシンクバイトＳｙに対して、上述したような偏心マージン付きの図１１の（ｂ）に示すバイトシンク検出窓でシンクバイト検出を行う場合に、図１１の（ｃ）に示すように正常にシンクバイト検出されれば、図１１の（ｄ）のようなＲＧパルスが得られる。ところが、図１１の（ｅ）に示すように、シンクバイトの誤検出が生じた場合には、シンクバイト誤検出のタイミングが最大２ΔＬｒｇ＿ｓｔａｒｔ＋２ΔＬｗｇ＿ｓｔａｒｔだけ遅れるため、図２のフォーマット時刻管理用シーケンサ２１はデータセクタの終端位置を最大２ΔＬｒｇ＿ｓｔａｒｔ＋２ΔＬｗｇ＿ｓｔａｒｔだけ遅れて認識することがあり、図１１の（ｆ）に示すＲＧパルスのように、ＲＧパルス終了位置が最大２ΔＬｒｇ＿ｓｔａｒｔ＋２ΔＬｗｇ＿ｓｔａｒｔだけ遅れることになり、これによる悪影響を防止するために、図１１の（ｇ）に示すように、当該データセクタＤ_ｎに続く、次のデータセクタＤ_ｎ＋１との間に、２ΔＬｒｇ＿ｓｔａｒｔ＋２ΔＬｗｇ＿ｓｔａｒｔだけギャップマージンを挿入する必要がある。すなわち、セクタ間のギャップには、最低限必要なギャップに対し、セクタ直後のギャップマージンΔＬｇａｐ＿ｅｎｄおよびバイトシンク窓用マージンと２ΔＬｒｇ＿ｓｔａｒｔ＋２ΔＬｗｇ＿ｓｔａｒｔを加えたものになる。
【００６０】
これに対して、本発明の実施の形態のサーボ同期型データ記録・再生方式を用いた場合、ΔＬｒｇ＿ｓｔａｒｔおよび、ΔＬｗｇ＿ｓｔａｒｔを共にゼロとすることが可能なため、余分のマージンを必要としない。つまり、本発明の実施の形態の方式を適用することで、セクタ間のギャップに２ΔＬｒｇ＿ｓｔａｒｔ＋２ΔＬｗｇ＿ｓｔａｒｔを挿入する必要がなく、フォーマット効率を向上させることが可能となる。
【００６１】
以上説明した本発明の実施の形態となるディスク装置は、以下の（１）、（２）、（３）に記載した記録再生技術を前提とし、新たに以下の工夫（４）を施したものである。
【００６２】
（１）ディスク回転に同期するサーボクロックを常時生成する。
ディスク偏心によって、このサーボクロックの周波数はディスク回転に同期して正弦波状に変化する。
【００６３】
（２）このサーボクロックを基準とし、周波数シンセサイザなどを用いて、周波数がディスク回転に同期して変化するデータ記録用クロックを生成する。
【００６４】
（３）ＲＧやＷＧなどフォーマット時刻制御用パルスは、（２）のデータ記録用クロックを用いて生成する。
【００６５】
（４）データ再生クロック生成用ＰＬＬは、セルフクロック再生を行わない平常時には、（２）のデータ記録用クロックに周波数同期させておき、データ再生を行う時のみ、再生信号に同期させる。
【００６６】
以上の工夫によって、ＲＧパルス、ＷＧパルス、記録データクロック及び再生データクロック周波数基準の全てが、偏心変化によるデータレート周波数変化に同期して変化する。よって、ギャップやプリアンブルにおいて、データレート周波数変化による時刻変化を吸収するための冗長度が不要になり、トラックフォーマットの効率が改善される。特に、ディスク着脱により偏心の変化が避けられないリムーバブルディスク装置においても、固定ディスク型のＨＤＤなど偏心変化が無い場合と同程度のギャップ長やプリアンブル長のフォーマットを用いることができるので、記憶容量を大きくすることができる。あるいは、偏心量が大きいディスクを着脱しても、セルフクロック用データ再生ＰＬＬの同期不良が起きにくく、バーストエラーが削減されるので、リムーバブルディスク装置のデータ信頼性を大幅に改善する効果がある。なお、本発明は、一般的な平坦磁性膜を持つ磁気ディスクを用いるので、特別なディスクを必要とせず、固定ＨＤＤおよびリムーバブルＨＤＤなどの磁気ディスク装置に広く適用可能である。
【００６７】
【発明の効果】
本発明は、データを記録するデータ領域と時刻基準情報を含むサーボ情報を記録するサーボ領域とが円周方向に交互に配置されたディスク状記録媒体に対して記録／再生を行い、上記時刻基準情報からディスク回転に同期したサーボクロックを生成するサーボクロック生成手段を備え、データ記録／再生処理期間を示すゲート信号及びデータ記録用ビットクロックが上記サーボクロックに同期しているディスク装置であって、各データアクセス単位にて独立にセルフクロック方式によりデータ再生用ビットクロックを生成するデータクロック生成手段を有し、このデータクロック生成手段の発振周波数を、当該データ再生処理期間を除いて、上記サーボクロック生成手段からのサーボクロックに同期させることにより、データ記録／再生処理期間を示すゲート信号、記録データクロック及び再生データクロック周波数基準の全てが、偏心変化によるデータレート周波数変化に同期して変化する。よって、ギャップやプリアンブルにおいて、データレート周波数変化による時刻変化を吸収するための冗長度が不要になり、トラックフォーマットの効率が改善される。特に、ディスク着脱により偏心の変化が避けられないリムーバブルディスク装置においても、固定ディスク型のＨＤＤなど偏心変化が無い場合と同程度のギャップ長やプリアンブル長のフォーマットを用いることができるので、記憶容量を大きくすることができる。あるいは、偏心量が大きいディスクを着脱しても、セルフクロック用データ再生ＰＬＬの同期不良が起きにくく、バーストエラーが削減されるので、リムーバブルディスク装置のデータ信頼性を大幅に改善する効果がある。
【図面の簡単な説明】
【図１】本発明の実施の形態となるディスク装置に用いられる磁気ディスクの構成例を示す図である。
【図２】本発明の実施の形態となるディスク装置のデータ記録／再生チャンネルの回路構成例を示すブロック図である。
【図３】記録トラック上のサーボセグメント及びデータセグメントの配列の例を示す図である。
【図４】データセグメント内のデータセクタと該データセクタを再生処理する期間を示すＲＧパルスとを示す図である。
【図５】データセグメント内のデータセクタと該データセクタを記録処理する期間を示すＷＧパルスとを示す図である。
【図６】固定クロック同期型の場合のセクタ間ギャップの偏心マージンを説明するための図である。
【図７】サーボクロック同期型の場合のセクタ間ギャップを示す図である。
【図８】固定クロック同期型の場合のデータセクタ内の偏心マージン付きのプリアンブルを示す図である。
【図９】固定クロック同期型の場合のデータセクタ内のプリアンブルの偏心マージンが必要となる理由を説明するための図である。
【図１０】固定クロック同期型の場合のバイトシンク検出窓に偏心マージンが必要となる理由を説明するための図である
【図１１】偏心マージン付きのバイトシンク検出窓を用いた場合にセクタ間ギャップに偏心マージンが必要となる理由を説明するための図である。
【図１２】従来のディスク装置のデータ記録／再生チャンネルの回路構成例を示すブロック図である。
【図１３】リムーバブルディスク装置の場合のディスク中心とスピンドル回転中心との偏心を示す図である。
【図１４】ディスク中心とスピンドル回転中心との偏心によるトラックとヘッドとのずれを示す図である。
【符号の説明】
１ 磁気ディスク、 ２ 磁気ヘッド、 ３ アンプ（Ｒｅａｄ Ｈｅａｄ Ａｍｐ．）、 ４ サーボクロック位相検出回路、 ５ サーボクロック生成用ＰＬＬ回路、 ６ 周波数シンセサイザＰＬＬ回路、 ７ アンプ（Ｗｒｉｔｅ Ａｍｐ．）、 １０ データ再生チャンネル信号処理系、 １１ データクロック生成用ＰＬＬ、 １７切換スイッチ、 ２０ コントローラ、 ２１ フォーマット時刻管理用シーケンサ、 ２５ ＥＣＣ符号器復号器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a disk device such as a magnetic disk device and a magneto-optical disk device, and more particularly to a disk device suitable for application to a device that performs recording and reproduction on a removable disk that can be removed and replaced.
[0002]
[Prior art]
In the current high-density magnetic disk devices, both the fixed disk type device (HDD) and the removable disk type device mostly use a combination of the sector servo system, the zone bit recording system and the self-clock type data reproducing system. I have.
[0003]
The sector servo method is disclosed in, for example, Patent Document 1 and Non-Patent Document 1. In this sector servo format, servo areas are provided radially from the center of the disk so that concentric data tracks on the disk surface are cut at substantially equal intervals. In each servo area, a position signal pattern and a track address required for head positioning are recorded, but the phases of the recording signals in each servo area are independent of each other, and there is no phase consistency. Each time the servo area is reproduced, the time synchronization for reproducing the servo recording signal is restored. As disclosed in Patent Literature 2, a servo clock may be generated based on a servo reproduction signal in servo position signal detection, and the detection may be performed in synchronization with the servo clock. It is started anew independently each time it is played.
[0004]
Next, a zone bit recording method is disclosed in Patent Document 3. This zone bit recording method divides the disk surface into a plurality of zones in the radial direction, makes the data rate almost proportional to the radius, and makes the linear recording density of the data almost constant regardless of the radius, thereby obtaining the data on the disk surface. The recording capacity can be maximized.
[0005]
FIG. 12 shows a block diagram of a data recording / reproducing system and a timing management system of an HDD in which a sector servo system and a zone bit recording system are combined. A data clock used for recording data in a data segment cut by a servo area (not shown) of the disk 1 has a fixed frequency and a fixed phase. In other words, this data clock is based on a fixed frequency clock (frequency f0) such as an output from the crystal oscillator 101, and a frequency synthesizer PLL (Phase Locked Loop) circuit 102 generates a data clock having a rational frequency fw. Used. That is, when natural numbers M and N are given to the frequency synthesizer PLL circuit 102 by a CPU (not shown), the relational expression
fw = f0 * M / N
Determines the data rate fw.
[0006]
At the time of data reproduction, each time a new data segment arrives, the data reproduction channel signal processing system 110 synchronizes the data clock generation PLL circuit 111 with the preamble recorded at the head of the data segment, and generates a data clock generation signal. A so-called self-clock method is used in which the data detection circuit is operated using a data bit clock (frequency fr) generated by the PLL circuit 111. Here, the data clock generating PLL circuit 111 is synchronized with the above-mentioned fixed frequency data clock during the time when synchronization with the reproduction signal is not performed.
[0007]
The system that combines the sector servo format described above with fixed-frequency synchronous data recording and self-clock data reproduction is easy to design because the operations of the servo system and data system are independent. However, there is an advantage that a high-precision bit clock synchronization can be obtained even if the linear recording density is high, and it is widely used in HDDs. Once a disk is mounted on the spindle shaft, such as an HDD, it will not be removed until the life of the disk drive. In addition, in a disk drive that performs servo write operation after the disk is mounted, the center of the concentric circle of the data track and the rotation center of the spindle will be the same. There is no eccentricity, or even a slight amount of misalignment during use of the device. Therefore, there is almost no head-disk relative speed fluctuation caused by a change in track radius due to eccentricity. Therefore, even if recording is performed with a fixed clock during data recording, the reproduced signal has the same fixed frequency. Therefore, the data reproducing PLL is synchronized with the data recording clock except when reproducing the data segment. There is no frequency deviation at the time of starting. That is, the data reproduction PLL only needs to establish phase synchronization in the synchronization establishment repetitive recording pattern (preamble) provided at the head of the data segment, which is easy.
[0008]
[Patent Document 1]
U.S. Pat. No. 4,032,984
(US Pat. No. 4,032,984, JB Kazer et al., “Transducer Positioning System for Providing both Coarse and Fine Positioning”, Apr. 28, 1975).
[Patent Document 2]
U.S. Pat. No. 5,089,757
(USP 5,089,757, Rosser C. Wilson, "Synchronous Digital Detection of Position Error Signal", Mar. 15, 1991).
[Patent Document 3]
U.S. Pat. No. 4,894,734
(US Pat. No. 4,894,734, Al Fischer and Ross Wilson, "Method and Apparatus for Constant Density Recording", May 15, 1987).
[Non-patent document 1]
C. Maury, “High track density for magnetic disk drives with an“ Embedded Servo ”positioning system”, IEEE Trans. Magn. , Vol. MAG-17, No. 4, pp. 1396-1402, July 1981
[0009]
[Problems to be solved by the invention]
[Frequency shift and time shift caused by eccentricity change]
On the other hand, in the case of the removable disk device, the eccentricity occurs due to the fitting of the disk and the spindle shaft. However, the chucking angle is not controlled and is determined almost at random. As shown in FIG. As a result, eccentricity having a magnitude Rd and a phase θd that differs for each attachment / detachment occurs at the disk center Cd. That is, the phase and magnitude of the eccentricity differ between the time of recording and the time of reproduction. In the following, it is assumed that the original track radius is R0, and the disc center Cd and the track center coincide with each other for the sake of simplicity. At this time, the dashed circle in FIG. 13 indicates the head trajectory, and the solid circle indicates the data recording track trajectory on the disk.
[0010]
Assuming that the magnitude of the eccentricity is Rdw and the phase is θdw at the time of data recording, the radius Rw (t) of the data recording track viewed from the spindle rotation center Cs is approximately when Rdw << R0,
Rw (t) = R0 + Rdw cos (ωt−θdw)
As shown in FIG. 14, the time varies in a sinusoidal manner within one round. Since the relative speed between the head and the disk changes in a sinusoidal manner in proportion to the radius, even if recording is performed at a constant data rate fw, a sinusoidal density distribution occurs in the linear recording density on the recording track.
[0011]
When the recorded disc is attached to and detached from the spindle shaft and reproduced, if the magnitude of the eccentricity is Rdr and the phase is θdr, the track radius is
Rr (t) = R0 + Rdr cos (ωt−θdr)
It changes according to.
[0012]
Under the influence of the eccentricity at the time of recording and the eccentricity at the time of reproduction, the data reproduction signal frequency changes in a sine wave shape. This change is greatest when the eccentric phase during recording and during reproduction is 180 degrees opposite. In this case, the reproduction data rate becomes
Frmax = fw (1+ (Rdr + Rdw) / R0),
Frmin = fw (1- (Rdr + Rdw) / R0)
Take the maximum value Frmax and the minimum value Frmin represented by
[0013]
For example, when the magnitude of the eccentricity is Rdr = Rdw = 50 μm and the original track radius is R0 = 10 mm, the maximum value of the frequency change is ± 1%.
[0014]
The data reproduction PLL needs to follow this time change. In particular, when a PLL that has been synchronized with a data recording clock of a constant frequency fw in a state where a reproducing operation is not performed reproduces a certain data segment, the PLL differs depending on the angle of existence of the data segment to be reproduced. It must respond to large frequency steps and settle. The larger the frequency step, the longer it takes to complete frequency synchronization and complete phase synchronization.
[0015]
[Effect of eccentricity on preamble length and decrease in format efficiency]
In order for the data recovery PLL, which is normally synchronized with the crystal oscillator-based fixed frequency clock, to settle until a sufficiently small phase error is obtained even for the maximum frequency step, a considerably long preamble is required. is there. No matter which data segment this maximum frequency step occurs in, in order to establish synchronization normally, it is necessary to provide a long preamble of the same length for the maximum frequency step in all data segments. There is a problem that the useless area increases and the utilization efficiency decreases.
[0016]
[Degradation of disk compatibility due to eccentricity]
Conversely, if the preamble length and the gap length before and after the data segment are not provided sufficiently long in the format, a burst error due to poor synchronization of the data PLL occurs when the eccentric change between recording and reproduction is large, There is a problem that data reliability is reduced.
[0017]
[Servo surface servo method]
As a conventional technique different from the above-mentioned conventional general technique, there is a servo surface servo method used until the 1980s. This method is disclosed, for example, in US Pat. No. 4,122,501 (US Pat. No. 4,122,501, FJ Sordello, “System for Recording and Reading Back Data on a Recording Media”, October 24, 1978). Have been. In this method, a dedicated disk surface for a servo pattern and a dedicated reproducing head are provided, a servo clock synchronized with the rotation of the disk is generated from a reproduced signal, a clock for data recording is generated in synchronization with the generated servo clock, and used for recording and used for recording. It was used as a frequency reference for the self-clock PLL. In this technique, the clock frequency for data recording follows the linear velocity fluctuation due to the rotation frequency fluctuation or the like, so that the center frequency of the self-clock PLL is always synchronized with the reproduction data rate that also varies in proportion to the linear velocity. Therefore, self-clock synchronization can be established using a short preamble. The disadvantage is that a dedicated disk surface and a dedicated head must be provided.
[0018]
[Servo clock synchronous recording method]
A servo clock synchronous recording method is an improvement of the above-mentioned conventional general clock method only. This method is disclosed, for example, in a disk drive disclosed in Japanese Patent Application Laid-Open No. 8-138329.
[0019]
In a disk device, a read gate (Read Gate, hereinafter) for instructing a recording / reproducing channel circuit of a start time and an end time of a data reproducing operation in each data segment as a time signal for instructing a format division on one round of a data track. RG), and a write gate (hereinafter, referred to as WG) pulse for instructing the time of the data recording operation. In the conventional fixed frequency synchronous data recording method, these pulses are generated in synchronization with a fixed frequency clock based on a crystal oscillator, so that the generation time is fixed. In contrast, the time at which the reproducing head travels on each data segment fluctuates back and forth due to the linear velocity change due to the eccentricity change of the track reproduction signal. Therefore, as a track format, it is necessary to provide a sufficiently wide gap before and after the data segment so that even if this time variation occurs, there is no interference between the preceding and following data segments or between the servo segments. This also causes a problem that a useless area increases in the track format.
[0020]
Therefore, in the servo clock synchronous recording method, a servo clock is generated by synchronizing a dedicated PLL with a reproduction signal of the clock mark in a plurality of servo areas radially provided at substantially equal angular intervals on a disk as a time reference. . In synchronization with this servo clock, the format time management sequencer 121 of the controller 120 in FIG. 12 generates various timing signals such as RG pulses and WG pulses, and also generates a data recording bit clock. Therefore, the time of the RG pulse and the WG pulse fluctuates in accordance with the fluctuation of the data segment appearance time due to the eccentricity, the frequency of the data recording bit clock also fluctuates, and the angular arrangement of the data recording bits on one round of the track is eccentric. It is almost constant without being affected by Therefore, the gap length can be reduced, and the useless area of the track format can be reduced.
[0021]
However, the technology disclosed in Japanese Patent Application Laid-Open No. 8-138329 has a configuration in which a data reproduction bit clock is also synchronized with a servo clock. Therefore, the accuracy of the data reproduction clock is determined by the accuracy of the servo clock jitter, and when the linear recording density of data is improved and the time length of one bit is shortened, the bit error rate is degraded. .
[0022]
Another configuration example of the servo clock synchronous data recording method is disclosed in an information recording apparatus disclosed in Japanese Patent Application Laid-Open No. 3-250464. In this example, clock pits are formed in a sector servo area by a concavo-convex pattern, and a data recording clock is generated by a PLL based on those times, so that it is possible to cope with linear velocity fluctuations in the same manner as the servo surface servo method. In addition, since the self-clock system is used, it is considered that the accuracy of the data reproduction bit clock can be maintained even when the linear recording density increases. However, in the servo area other than the data segment to be reproduced, the self-clock PLL holds the oscillation frequency. However, if the eccentricity is large and the frequency of the reproduced signal is large before and after the section, the PLL after the data reproduction is resumed. Has a problem that it takes a long time to settle because it generates a frequency step response. Further, the present invention has a disadvantage that a special uneven pattern disk is premised.
[0023]
The present invention has been made to solve the above-described problems of the related art, and can reduce the frequency pull-in settling time at the time of initial synchronization and improve the format efficiency even in the case where the eccentricity can occur due to a removable disk. It is an object of the present invention to provide a disk device capable of improving and at the same time reducing a burst error rate due to loss of synchronization.
[0024]
[Means for Solving the Problems]
The disk device according to the present invention uses a servo clock synchronous data recording method and a self-clock type data reproduction method as a premise, thereby newly ensuring high format efficiency and a good error rate at a high linear recording density, By synchronizing the self-clock PLL to a rational multiple of the frequency of the servo clock during non-data reproduction, shortening the frequency pull-in settling time at the time of initial synchronization and improving format efficiency, and at the same time, reducing the burst error rate due to loss of synchronization It is.
[0025]
That is, in order to solve the above-described problems, the present invention provides a disk-shaped recording apparatus in which a data area for recording data and a servo area for recording servo information including time reference information are alternately arranged in a circumferential direction. A servo clock generating means for recording / reproducing on / from the medium and generating a servo clock synchronized with the rotation of the disk from the time reference information; A disk device synchronized with a servo clock, comprising data clock generating means for generating a data reproduction bit clock independently by a self-clock method in each data access unit, and setting an oscillation frequency of the data clock generating means to , Except for the data reproduction processing period, the servo clock from the servo clock generation means. It is characterized by synchronizing to.
[0026]
Here, the data area and the servo area are a data segment and a servo segment, respectively, and the data access unit is a data sector, and the data clock generating means synchronizes with a preamble arranged at a head portion in the data sector. Generating a bit clock for data reproduction.
[0027]
Further, a changeover switch is provided on the input side to the data clock generation means, and during the data reproduction processing period, the clock component of the reproduction signal in the data access unit is sent. It is preferable to perform switching control so as to transmit the servo clock of (1).
[0028]
The disk-shaped recording medium is preferably a removable disk that can be removed and replaced, but it is a matter of course that the present invention can be applied to a fixed disk device (HDD).
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of a disk drive according to the present invention will be described with reference to the drawings.
[0030]
[Description of Synchronous Servo Disk Format]
FIG. 1 shows a configuration example of a magnetic disk 1 used in an embodiment of a disk drive according to the present invention. The magnetic disk 1 has a flat magnetic film, and is provided with approximately 100 or more servo areas at regular intervals in the circumferential direction. In each servo area, a clock mark, a track address pattern (access pattern), a position signal pattern (fine pattern), and the like are recorded in advance on a flat magnetic film of a medium using a servo writer as magnetization reversal. In this embodiment, the servo area and the data area respectively correspond to a servo segment and a data segment described later. The data is recorded in the data area using the data sector as an access unit. However, the length of the data area and the length of the data sector are independent, and one or more data sectors are included in the data area, and one data sector is included in the data area. A data sector may be arranged over two data areas.
[0031]
[Description of block diagram of servo clock synchronous data recording / reproducing operation]
FIG. 2 shows a configuration example of a data recording / reproducing channel of the magnetic disk device according to the embodiment of the present invention.
[0032]
In FIG. 2, a magnetic disk 1 is driven to rotate at a frequency fspin [Hz] by a spindle motor (not shown), and a clock mark reproduction signal reproduced by the magnetic head 2 from the magnetic disk 1 is supplied to an amplifier (Read Head). Amp.), And is input to the servo clock phase detection circuit 4. Based on the phase detection result from the servo clock phase detection circuit 4, a servo clock generation PLL (Phase Locked Loop) circuit 5 generates a servo clock synchronized with the disk rotation. This servo clock has a center frequency fsv, and when there is eccentricity between the track center of the magnetic disk 1 and the spindle rotation center, the frequency fluctuates in a sine wave shape. A feature of the embodiment of the present invention is that all the data clocks in the recording and reproducing operations and the timing signals indicating the start time and the end time of the recording / reproducing operation are synchronized with the servo clock.
[0033]
The frequency synthesizer PLL circuit 6 generates a data recording clock (central frequency equal to the data rate of each recording / reproduction target data zone of the magnetic disk 1 concentrically divided into zones based on the servo clock (central frequency fsv)). Frequency fw). These frequencies fsv and fw have a relationship of fw = fsv * M / N by integers M and N given by the CPU according to the zone number. The data recording clock is also input to the data clock generation PLL circuit 11 in the data reproduction channel signal processing system 10 as a frequency reference. It is also provided to the controller 20 and is used as an operation clock of a format time management sequencer 21 for managing the time of the track format on the disk.
[0034]
When performing data recording, first, data is given from the host PC (personal computer) 22 to the controller 20 via the host I / F circuit 23. The controller 20 temporarily stores the data in the buffer memory 24, adds the ECC code in the ECC encoder / decoder 25, and uses the format time management sequencer 21 to convert the data sector including the preamble and the byte synchronization pattern. After completion, the data is output to the amplifier (Write Amp.) 7 as write data (WD). In parallel with this, the format time management sequencer 21 generates a write gate (WG) pulse indicating the time from the start to the end of the recording, and defines the recording current output time width of the amplifier 7.
[0035]
Therefore, even if the linear velocity fluctuates due to disk eccentricity, the clock frequency for data recording and the times of various pulses for format management also fluctuate in proportion to the linear velocity, so that the data recording position on the track is affected by the eccentricity. Absent.
[0036]
When performing data reproduction, first, a format time management sequencer 21 of the controller 20 generates a read gate (Read Gate: RG) pulse period (data reproduction processing period) that substantially covers a data access unit (data sector) to be reproduced. , An amplifier (Read Head Amp.) 3 outputs a reproduction signal. The reproduction signal from the amplifier 3 is converted into a digital signal by an A / D converter 14 through signal amplitude normalization and equalization by an AGC circuit 12 of a data reproduction channel signal processing system 10, and is converted into a channel signal by a Viterbi detector 15. The data is detected and further converted by the channel decoder 16 into NRZ data (write data: RD). The NRZ data (RD) is input to the controller 20, and only the user data portion is cut out of the data sector according to the instruction of the format time management sequencer 21, and the decoding process (error detection and correction) by the ECC encoder / decoder 25 is performed. Is output to the host I / F circuit 23.
[0037]
In the above series of data reproducing operations, the channel clock (frequency fr) for synchronizing the channel bits is obtained by adding the clock of the data clock generating PLL circuit 11 to the reproduced signal of the preamble area recorded at the head of each data segment. It is generated by a so-called self-clocking method for synchronizing.
[0038]
Specifically, a changeover switch 17 is provided on the input side of the data clock generation PLL circuit 11, and the output from the A / D converter 14 (clock in the reproduced signal) during the RG pulse period (data reproduction processing period). The output from the frequency synthesizer PLL circuit 6 is switched and selected when the component is outside the RG pulse period, and is input to the data clock generation PLL circuit 11.
[0039]
Hereinafter, the most different point of the embodiment of the present invention from the conventional general technology will be described.
[0040]
As described above, the data clock generation PLL circuit 11 switches the synchronization target signal according to the RG pulse (read gate pulse). In other words, during a time when the self-clock synchronization operation is not performed (for example, a servo area, a non-reproduction target data sector or segment, and a trace period of a gap between data sectors), it is synchronized with a data recording clock which is a frequency reference, The center frequency fr is always synchronized with the fluctuation of the disk rotation speed. In a period during which the RG pulse is active (data reproduction processing period), that is, during a period in which a self-clock operation is performed to reproduce the data sector, the RG pulse is synchronized with the data sector reproduction signal. Here, the data rate changes in a sinusoidal manner due to linear velocity fluctuations due to eccentricity and rotation frequency change, but when the RG pulse changes to Active, and when synchronization with the head of the data sector starts, the data rate is exactly the same. Since it is synchronized with a data recording clock indicating a sinusoidal frequency change, there is no frequency deviation between the two. In other words, the PLL for data clock reproduction does not need to resynchronize the frequency in the preamble at the head of the data sector, and only needs to establish the phase synchronization. Therefore, since the establishment of synchronization can be completed in a short time, the preamble can be shortened, and the track use efficiency in the format can be improved.
[0041]
[Format comparison between servo clock synchronous data recording and conventional fixed clock synchronous data recording]
In the servo clock synchronous data recording method presupposed by the present invention, in addition to the shortening of the initial synchronizing time for the data reproducing synchronizer according to the embodiment of the present invention, there is also an advantage that the eccentric margin time of various timing signals for format management can be reduced. is there. Both are advantages that can be used at the same time, and contribute to an overall improvement in format efficiency. Hereinafter, the latter advantage will be described.
[0042]
In the servo clock synchronous data recording / reproducing, the recording / reproducing start time and the recording / reproducing time width at the time of recording / reproducing are defined by the WG pulse and the RG pulse generated by the track format time management sequencer in the controller. . A description will be given of the variations of the gap length margin, preamble length margin, and byte sync detection window margin necessary to absorb the above-mentioned recording / reproducing timing fluctuations instructed by the WG and RG due to the eccentricity. Will be described below.
[0043]
As described above, the area on the track is divided into servo segments (servo areas) arranged at equal intervals and data segments (data areas), which are areas for recording and reproducing data between the servo segments. That is, as shown in FIG. 3, the servo segments SS and the data segments DS are alternately arranged continuously on the track, and the user data is recorded only in the data segment DS. On the other hand, the track format time management sequencer 21 performs recording and reproduction on the data segment in data units called data sectors defined independently of the servo segment SS and the data segment DS.
[0044]
Therefore, the start / end position of the data sector is irrelevant to the start / end position of the data segment DS, and the actual start / end position of the data sector is different for each data segment DS. Here, FIG. 3 shows the data sector D in the data segment DS. _n And a plurality of data sectors are included in one data segment DS, or one data sector (for example, D _{n + 1} ) Are placed. For this reason, the start position and the end position of the RG pulse / WG pulse for performing reproduction or recording in data sector units are almost always in the middle of the data segment DS. Requires a margin in order to absorb fluctuations in the generation timing of the RG pulse / WG pulse at the position. In general, as a structure in a data sector, for example, as shown in FIG. 3, a preamble Pr and a synchronization signal (sync byte) Sy are provided at a start portion of the data sector, and an error check code ECC is provided at an end portion. Etc. are provided.
[0045]
Here, the necessity of the gap margin due to the fluctuation of the RG pulse / WG pulse in the case of the above-mentioned conventional fixed clock synchronization type, and the margin reduction effect in the embodiment of the present invention will be described.
[0046]
The physical length Lseg and the time length Tseg of the data segment when there is no eccentricity are constant for each track. While the data segment physical length Lseg when eccentricity is present is constant, the time length per data segment varies as follows. As described in the problem of the conventional method, similarly to the data rate fluctuation, the maximum value Tseg_max and the minimum value Tseg_min of the time length per data segment are:
Tseg_max = Tseg (1+ (Rdr + Rdw) / R0)
Tseg_min = Tseg (1− (Rdr + Rdw) / R0)
It is represented by the following equation. Here, R0 represents the original track radius, Rdr represents the magnitude of the eccentricity at the time of reading, and Rdw represents the magnitude of the eccentricity at the time of writing.
[0047]
As shown in FIG. 4, the RG pulse start / end positions (physical lengths) from the data segment head position P0 when there is no RG pulse variation due to eccentricity are Lrg_start and Lrg_end. Similarly, as shown in FIG. Lwg_start and Lwg_end are the WG pulse start / end positions (physical lengths) from the data segment head position P0 when there is no WG pulse fluctuation due to eccentricity. In the conventional method, since a fixed frequency clock is used, the number of fixed frequency clocks per data segment also fluctuates due to eccentricity. Since the start / end position of the RG pulse / WG pulse is determined by counting the fixed frequency clock, when the eccentricity exists, the start / end position of the RG pulse / WG pulse fluctuates. The start position fluctuation ΔLrg_start of the RG pulse due to the eccentricity, the end position fluctuation ΔLrg_end of the RG pulse, the start position fluctuation ΔLwg_start of the WG pulse, and the end position fluctuation ΔLwg_end of the WG pulse are:
ΔLrg_start = Lrg_start × Rdr / R0
ΔLrg_end = Lrg_end × Rdr / R0
ΔLwg_start = Lwg_start × Rdw / R0
ΔLwg_end = Lwg_end × Rdw / R0
It is required as follows.
[0048]
Therefore, for example, the starting position of the RG pulse from the data segment head position P0 is determined by the influence of eccentricity.
Lrg_start-ΔLrg_start to Lrg_start + ΔLrg_start
Between the positions. The end position of the RG pulse from the data segment head position P0 is
Lrg_end−ΔLrg_end to Lrg_end + ΔLrg_end
Between the positions. That is, as shown in FIG. 4, an eccentricity margin is required by ΔLrg_start before the start position of the RG pulse, and an eccentricity margin is required by ΔLrg_end after the end position of the RG pulse.
[0049]
Similarly, as for the start / end position of the WG pulse from the data segment head position P0, as shown in FIG. 5, an eccentric margin by ΔLwg_start is required before the start position of the WG pulse, and the end of the WG pulse After the position, a margin for eccentricity is required by ΔLwg_end.
[0050]
From the above, the gap margin required in the format, that is, the gap margin ΔLgap_start immediately before the data sector and the gap margin ΔLgap_end immediately after the data sector with respect to the minimum gap gp between the data sectors shown in FIG. Is
ΔLgap_start = MAX (ΔLrg_start, ΔLwg_start)
ΔLgap_end = MAX (ΔLrg_end, ΔLwg_end)
become that way.
[0051]
When the servo-synchronous data recording / reproducing method according to the embodiment of the present invention is used, the time length per data segment when eccentricity exists fluctuates similarly to the above-described Tseg_max and Tseg_min. The number of clocks per clock segment is constant. Since the start / end position of the RG pulse / WG pulse is determined by counting the servo synchronization clock, the start / end position of the RG pulse / WG pulse does not change even when the eccentricity exists. That is, as shown in FIG. 7, the start / end positions of the RG pulse / WG pulse are fixed positions, ΔLrg_start, ΔLrg_end, ΔLwg_start, and ΔLwg_end can be set to zero, and the minimum required gap between data sectors can be set. It is possible to eliminate the eccentricity margin for gp. That is, it is possible to improve the format efficiency by applying the method of the embodiment of the present invention.
[0052]
Next, the necessity of the preamble margin due to the fluctuation of the RG pulse / WG pulse and the effect of reducing the eccentric margin in the embodiment of the present invention will be described. As shown above, due to the eccentricity, the RG pulse / WG pulse becomes
RG pulse start position: maximum ΔLrg_start fluctuation before and after
WG pulse start position: maximum ΔLwg_start fluctuation before and after
It fluctuates like
[0053]
Here, it is known that a preamble of a predetermined length Lpre is required from the position where the RG pulse starts, and a preamble of this length must be ensured under any circumstances. Therefore, the preamble length in the presence of eccentricity is, as shown in FIG.
Lpre + 2ΔLrg_start + 2ΔLwg_start
It becomes. That is, in addition to the minimum required preamble length Lpre, an extra preamble having a length of 2ΔLrg_start + 2ΔLwg_start is required as an eccentricity margin.
[0054]
This is because, when the timing of the WG pulse is determined as shown in FIG. 9B with respect to the preamble recorded when there is no eccentricity shown in FIG. Since the position fluctuation ΔLwg_start occurs, the position fluctuation of the preamble recorded when there is eccentricity is as shown in FIG. 9C. In other words, recording is performed in which the preamble of (a) fluctuates by a maximum of ΔLwg_start before and after. For the recording in which such a change occurs, the timing of the RG pulse needs to be determined as shown in FIG. 9D in consideration of the position change ΔLrg_start of the RG pulse due to the eccentricity. In order to make it possible to reproduce a preamble having a length equal to or longer than the required preamble length Lpre, and to prevent a problem of reproducing an area in which nothing is recorded immediately before the preamble, the above-described operation is performed. That is, it is necessary to add a margin of the length of 2ΔLrg_start + 2ΔLwg_start to the minimum required preamble length Lpre.
[0055]
On the other hand, when the servo-synchronous data recording / reproducing method according to the embodiment of the present invention is used, as described above, both ΔLrg_start and ΔLwg_start can be set to zero. do not need. That is, by applying the method according to the embodiment of the present invention, the preamble length can be limited to Lpre, and the format efficiency can be improved.
[0056]
Next, the necessity of the byte sync detection window margin due to the fluctuation of the RG pulse / WG pulse and the effect of reducing the eccentric margin in the embodiment of the present invention will be described. Normally, a sync byte for synchronization in units of bytes is inserted immediately after the preamble pattern, and uses a format in which user data starts immediately after the sync byte. In order to detect a sync byte, a signal called a byte sync detection window indicating a section in which a detection operation is performed is used. That is, the detection operation is performed only when the byte sync detection window is active. The byte sync detection window is generated such that it becomes active after a predetermined length has elapsed with reference to the position where the RG pulse has started, and becomes active only for a predetermined length. It is desirable that the byte sync detection window be active in a section as short as possible to prevent erroneous detection. Here, in the case where there is no eccentricity, if it becomes active after a predetermined length Lsync_start from the RG pulse start position and remains active only for the section of Lsync_act, as shown in FIG. Is determined as follows.
[0057]
In FIG. 10, (a) shows the RG pulse, (b) shows the recording preamble fluctuation with eccentricity, (c) shows the byte sync window without eccentricity, and (d) shows the case with eccentricity. Are shown respectively. As is clear from FIG.

That is, in addition to the minimum required byte sync detection window length Lsync_act, an eccentricity margin
2ΔLrg_start + 2ΔLwg_start
Requires a byte sync detection window of length
[0058]
However, enlarging the byte sync detection window causes the following adverse effects. In other words, an increase in the sync byte detection operation time may result in erroneous detection of user data starting immediately after the sync byte as a sync byte, thereby increasing the probability of false detection of a sync byte. In addition, at the time of erroneous detection of the sync byte, the detection timing is delayed by a maximum of 2ΔLrg_start + 2ΔLwg_start, so that the RG pulse may overlap with the next data sector following the data sector. In order to prevent this, it is necessary to add a margin to the gap between data sectors.
[0059]
The addition of a margin to the gap between the data sectors will be described with reference to FIG. FIG. 11A shows a conventional format in which only the inter-sector gap gp is provided without eccentricity, and the data sector D of this format is shown. _n When the sync byte is detected in the byte sync detection window shown in FIG. 11B with the eccentric margin as described above for the sync byte Sy, the sync byte Sy is normally synced as shown in FIG. If a byte is detected, an RG pulse as shown in FIG. 11D is obtained. However, as shown in FIG. 11E, when an erroneous detection of the sync byte occurs, the timing of the erroneous detection of the sync byte is delayed by a maximum of 2ΔLrg_start + 2ΔLwg_start, so that the format time management sequencer 21 of FIG. May be recognized with a delay of 2ΔLrg_start + 2ΔLwg_start at the maximum, and the RG pulse end position is delayed by a maximum of 2ΔLrg_start + 2ΔLwg_start as in the RG pulse shown in FIG. As shown in FIG. 11 (g), the data sector D _n Following data sector D _{n + 1} , It is necessary to insert a gap margin by 2ΔLrg_start + 2ΔLwg_start. That is, the gap between the sectors is obtained by adding the gap margin ΔLgap_end, the margin for the byte sync window, and 2ΔLrg_start + 2ΔLwg_start immediately after the sector to the minimum required gap.
[0060]
On the other hand, when the servo-synchronous data recording / reproducing method according to the embodiment of the present invention is used, since both ΔLrg_start and ΔLwg_start can be set to zero, no extra margin is required. That is, by applying the method of the embodiment of the present invention, it is not necessary to insert 2ΔLrg_start + 2ΔLwg_start into the gap between sectors, and it is possible to improve the format efficiency.
[0061]
The disk device according to the embodiment of the present invention described above is based on the recording / reproducing technology described in the following (1), (2), and (3), and is provided with the following device (4). It is.
[0062]
(1) A servo clock synchronized with the disk rotation is always generated.
Due to the disk eccentricity, the frequency of the servo clock changes in a sine wave shape in synchronization with the disk rotation.
[0063]
(2) Using this servo clock as a reference, a data recording clock whose frequency changes in synchronization with disk rotation is generated using a frequency synthesizer or the like.
[0064]
(3) A pulse for format time control such as RG or WG is generated using the data recording clock of (2).
[0065]
(4) The PLL for generating a data reproduction clock is frequency-synchronized with the data recording clock in (2) during normal times when the self-clock reproduction is not performed, and is synchronized with the reproduction signal only when performing data reproduction.
[0066]
With the above-described measures, all of the RG pulse, the WG pulse, the recording data clock, and the reproduction data clock frequency reference change in synchronization with the data rate frequency change due to the eccentric change. Therefore, in a gap or a preamble, redundancy for absorbing a time change due to a data rate frequency change becomes unnecessary, and the efficiency of the track format is improved. In particular, even in a removable disk device in which a change in eccentricity is unavoidable due to the attachment / detachment of a disk, a format with a gap length and a preamble length similar to those in a case where there is no eccentricity change such as a fixed disk type HDD can be used. Can be larger. Alternatively, even if a disk having a large amount of eccentricity is attached or detached, synchronization failure of the self-clock data reproduction PLL hardly occurs and burst errors are reduced, so that the data reliability of the removable disk device is greatly improved. Since the present invention uses a magnetic disk having a general flat magnetic film, it does not require a special disk and can be widely applied to magnetic disk devices such as fixed HDDs and removable HDDs.
[0067]
【The invention's effect】
The present invention performs recording / reproduction on a disk-shaped recording medium in which a data area for recording data and a servo area for recording servo information including time reference information are alternately arranged in a circumferential direction. A disk device comprising: a servo clock generating unit configured to generate a servo clock synchronized with disk rotation from information; wherein a gate signal indicating a data recording / reproducing processing period and a data recording bit clock are synchronized with the servo clock. Data clock generating means for independently generating a bit clock for data reproduction by a self-clock method in each data access unit, and setting the oscillation frequency of the data clock generation means to the servo clock except for the data reproduction processing period. Data recording / reproducing processing is synchronized with the servo clock from the generating means. A gate signal indicating between, all of the recording data clock and reproducing data clock frequency reference is changed in synchronization with the data rate frequency variation due to the eccentricity variation. Therefore, in a gap or a preamble, redundancy for absorbing a time change due to a data rate frequency change becomes unnecessary, and the efficiency of the track format is improved. In particular, even in a removable disk device in which an eccentricity change cannot be avoided due to the attachment / detachment of the disk, a format having a gap length and a preamble length similar to a case where there is no eccentricity change such as a fixed disk type HDD can be used. Can be larger. Alternatively, even if a disk having a large amount of eccentricity is attached or detached, synchronization failure of the self-clock data reproduction PLL hardly occurs and burst errors are reduced, so that the data reliability of the removable disk device is greatly improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of a magnetic disk used in a disk device according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a circuit configuration example of a data recording / reproducing channel of the disk device according to the embodiment of the present invention.
FIG. 3 is a diagram showing an example of an arrangement of servo segments and data segments on a recording track.
FIG. 4 is a diagram showing a data sector in a data segment and an RG pulse indicating a period during which the data sector is reproduced.
FIG. 5 is a diagram showing a data sector in a data segment and a WG pulse indicating a period during which the data sector is recorded.
FIG. 6 is a diagram for explaining an eccentric margin of an inter-sector gap in the case of a fixed clock synchronous type.
FIG. 7 is a diagram showing an inter-sector gap in the case of a servo clock synchronous type.
FIG. 8 is a diagram showing a preamble with an eccentric margin in a data sector in the case of a fixed clock synchronous type.
FIG. 9 is a diagram for explaining why an eccentricity margin of a preamble in a data sector is required in the case of a fixed clock synchronous type.
FIG. 10 is a diagram for explaining the reason why an eccentricity margin is required for a byte sync detection window in the case of a fixed clock synchronous type.
FIG. 11 is a diagram for explaining the reason why an eccentricity margin is required for an inter-sector gap when a byte sync detection window with an eccentricity margin is used.
FIG. 12 is a block diagram showing a circuit configuration example of a data recording / reproducing channel of a conventional disk device.
FIG. 13 is a diagram showing eccentricity between a disk center and a spindle rotation center in the case of a removable disk device.
FIG. 14 is a diagram illustrating a deviation between a track and a head due to eccentricity between a center of a disk and a center of rotation of a spindle.
[Explanation of symbols]
1 magnetic disk, 2 magnetic head, 3 amplifier (Read Head Amp.), 4 servo clock phase detection circuit, 5 PLL circuit for servo clock generation, 6 frequency synthesizer PLL circuit, 7 amplifier (Write Amp.), 10 data reproduction channel Signal processing system, 11 PLL for data clock generation, 17 changeover switch, 20 controller, 21 sequencer for format time management, 25 ECC encoder decoder

Claims (6)

Data is recorded / reproduced on / from a disk-shaped recording medium in which a data area for recording data and a servo area for recording servo information including time reference information are alternately arranged in the circumferential direction. A disk device comprising a servo clock generating means for generating a servo clock synchronized with the servo clock, wherein a gate signal indicating a data recording / reproducing processing period and a data recording bit clock are synchronized with the servo clock.
Data clock generating means for independently generating a bit clock for data reproduction by a self-clock method in each data access unit, and setting the oscillation frequency of the data clock generation means to the servo clock except for the data reproduction processing period. A disk device synchronized with a servo clock from a generation unit. The data area and the servo area are a data segment and a servo segment, respectively, the data access unit is a data sector, and the data clock generating means is used for reproducing data synchronized with a preamble arranged at a head portion in the data sector. 2. The disk device according to claim 1, wherein a bit clock is generated. As an input signal to the data clock generation means, a clock component of a reproduction signal in the data access unit is transmitted during the data reproduction processing period, and a servo clock from the servo clock generation means is transmitted during periods other than the data reproduction processing period. 2. The disk device according to claim 1, wherein: 2. The disk device according to claim 1, wherein the disk-shaped recording medium is a removable disk that can be removed and replaced. 2. The disk device according to claim 1, wherein a gate signal indicating the data recording / reproducing processing period, the data recording bit clock, and a data segment arrangement reference time signal are synchronized with the servo clock. 2. The disk device according to claim 1, wherein the time reference information is recorded on a flat magnetic film in the servo area.

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