JP2007293988A - Magnetic disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic disk device for increasing efficiency of error correction by utilizing erasure correction thereby reducing an amount of use of an alternative sector. <P>SOLUTION: The magnetic disk device has: a magnetic disk medium; a reproduction part which reproduces data from a signal recorded on the magnetic disk medium; an error correction part which corrects errors which may be included in the reproduced data; and a recording part which records locations of the errors corrected in the error correction part, wherein the error correction part applies dissipation correction processing to the reproduced data when reading positions of the reproduced data are recorded as the locations of continuous errors in the recording part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic disk device such as a hard disk.

  In a magnetic disk device such as a hard disk drive, data is recorded as a magnetic signal on a magnetic recording medium, and data is read from the magnetic signal. Here, when data is read, a read error may occur in the bit string of the read data (so-called random error) even though the data is correctly recorded. This read error is corrected using the error correction code.

  In recent years, in error correction processing performed using an error correction code, information for specifying the position where an error has occurred (erasure pointer information (hereinafter referred to as EP)) is generated and stored, and later error correction processing is performed. For example, Patent Document 1 discloses a technique that can be used.

  In addition, a defect occurs in the magnetic recording medium itself after product shipment, and data cannot be recorded in the defective portion, and data recorded in the defective portion cannot be continuously read (so-called burst). Error) may occur. In this case, generally, measures are taken to stop the use of a sector in which a continuous read error (burst error) exceeds a predetermined burst determination threshold. That is, the sector in which the continuous error (burst error) occurs is regarded as a burst error occurrence location, along with the sector address (information indicating the position of the sector) in the defect sector table, instead of the sector. Are recorded in association with addresses of alternative sectors for recording data to be recorded.

Then, data to be recorded in the sector where the burst error has occurred is recorded in the alternative sector, and data is read out from this alternative sector during reproduction.
US Patent Application Publication No. 2004/153729

  However, in the above-described conventional magnetic disk device, the error correction code correction capability is used for the error correction of the burst error at the location where the burst error has occurred, so that the error of the random error cannot be corrected. Therefore, the current burst determination threshold is set low so as not to cause a problem in reading data.

  Therefore, in applications where data is easily recorded sequentially (such as a hard disk recorder), access to the alternative sector is likely to be frequent, affecting the recording / reproducing speed and complicating the circuit configuration for compensating for this.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic disk device that can improve the error correction efficiency by using erasure correction and reduce the usage amount of alternative sectors. One of them.

  The present invention for solving the problems of the conventional example is a magnetic disk device, a magnetic disk medium, a reproducing unit for reproducing data from a signal recorded on the magnetic disk medium, and the reproduced An error correction unit that corrects an error that may be included in the data; and a recording unit that records an occurrence position of the error corrected in the error correction unit, wherein the read position of the reproduced data is The erasure correction processing is performed on the reproduced data when the recording unit records the continuous error occurrence positions.

  In this way, erasure correction can be used to improve error correction efficiency and reduce the amount of alternative sectors used.

  Embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, a magnetic disk device according to an embodiment of the present invention includes a magnetic recording medium 1, a head unit 2, a head drive control unit 3, a read / write (RW) unit 4, and a control unit. 5 and a storage unit 6.

  The magnetic recording medium 1 is a disk-shaped magnetic recording medium. The magnetic recording medium 1 is supported by a support portion so as to be rotatable around the center of the disk, and is driven to rotate by a spindle motor SPM. The support unit that supports the magnetic recording medium 1 is fixed to the base of the housing.

  In the magnetic recording medium 1 of the present embodiment, tracks are formed concentrically, and each track is logically divided into sectors that are partitioned by boundaries extending radially from the center of rotation in the radial direction at predetermined angles. Yes.

  The head unit 2 includes at least one head assembly, and each head assembly includes a head corresponding to each recording surface of the magnetic recording medium 1 and an arm that supports each head. The head unit 2 is supported so as to be rotatable about the rotation center of the voice coil motor VCM.

  The head drive control unit 3 drives the voice coil motor VCM according to an instruction input from the control unit 5 and controls the positions of the recording head and the reproduction head included in the head unit 2.

  The RW unit 4 performs predetermined processing such as decoding on the data read from the magnetic recording medium 1 by the reproducing head, and outputs the data to the control unit 5. The RW unit 4 performs predetermined processing such as encoding data to be recorded input from the control unit 5 and records the data on the magnetic recording medium 1 via the recording head.

  When the RW unit 4 detects thermal asperity (TA) based on the data read by the reproducing head, the RW unit 4 outputs a TA detection signal. When the RW unit 4 detects an error that violates the encoding rule in the decoding process, the RW unit 4 outputs a signal indicating that the error has been detected. As the latter error, for example, there is an RLL violation which is an error related to the run length. In the following, signals for informing about these reading defects are collectively referred to as “error signals”.

  The control unit 5 is a microcomputer, for example, and operates according to a program stored in the storage unit 6. The control unit 5 is connected to a host computer or the like, generates and outputs an instruction for the head drive control unit 3 based on an instruction from the host side, and outputs data requested by the host side on the magnetic recording medium 1. Control is performed to move the head to the recorded location, and error correction processing or the like is performed on the data output from the RW unit 4 to output to the host side. Further, the control unit 5 generates and outputs an instruction to the head drive control unit 3 in accordance with a recording request from the host side, performs control to move the head to a position for recording data, and performs recording on the RW unit 4. Output the target data.

  The storage unit 6 includes a storage element such as a nonvolatile RAM or ROM, and holds a program executed by the control unit 5. In the present embodiment, a defect sector table that represents the position of occurrence of a continuous error (burst error position) that occurred later (after product shipment) is stored in this nonvolatile RAM. In this embodiment, erasure pointer information (EP) indicating the position where error correction has been performed is recorded as the burst error position.

  Here, error correction processing by the control unit 5 will be described. The error correction process of the control unit 5 of the present embodiment functionally includes a defect sector table management unit 21, a table conversion unit 22, and an error correction unit 23, as shown in FIG. Composed.

  When the data is read, the defect sector table management unit 21 sends continuous number information indicating the number of symbols related to the burst error together with the burst error detection signal from the table conversion unit 22 described later, and the symbol where the burst error starts. In response to the input of the start information indicating the position, the defect sector table is updated.

  In the present embodiment, as shown in FIG. 3, the defect sector table includes the sector number of the sector in which the subsequent burst error occurs, the start information that is the start position of the burst error, and the burst error It is associated with continuous number information, which is the number of consecutive symbols. Further, among sectors in which a burst error has occurred, those having an alternative sector are recorded in association with the alternative sector number of the alternative sector.

  When the table conversion unit 22 receives the input of the sector number for specifying the data sector from which the data is read, the table conversion unit 22 refers to the defect sector table and relates to the input sector number to cause a subsequent defect. It is checked whether information indicating that a burst error has occurred is recorded.

  For example, the table conversion unit 22 checks whether or not the alternative sector number of the alternative sector is associated with the input sector number (target sector number) in the defect sector table. Here, when the alternative sector number of the alternative sector is associated with the target sector number, the table conversion unit 22 gives an instruction to move the head to the alternative sector specified by the alternative sector number. Output to the control unit 3.

  If the alternative sector number of the alternative sector is not associated with the target sector number, it is further checked whether start information and continuous number information are associated with the target sector number. If start information and continuous number information are associated with each other, the information is read out, and an erasure flag signal is output to the error correction unit 23 in synchronization with a separately generated read / write control signal. The head drive control unit 3 is instructed to move the head to the sector specified by the sector number of interest.

  The table conversion unit 22 also outputs an erasure flag signal when the RW unit 4 outputs an error signal such as a TA detection signal or an RLL violation.

  Further, the table conversion unit 22 receives the start information output from the error correction unit 23 together with the correction end signal and the continuous number information when the error correction unit 23 outputs a correction end signal described later. A burst error detection signal is output to the defect sector table management unit 21. At this time, the continuous number information indicating the number of symbols related to the burst error and the start information indicating the start position of the burst error are output to the defect sector table management unit 21 together.

  When writing data, the error correction unit 23 reads data input from the host side in synchronization with the read / write control signal, and calculates and generates an error correction code for the data. Then, the error correction unit 23 attaches the generated error correction code to the corresponding data and outputs it to the RW unit 4.

  The error correction unit 23 reads data output from the RW unit 4 in synchronization with the read / write control signal when reading data. At this time, if the table conversion unit 22 does not output the erasure flag signal, the error correction unit 23 performs a process of correcting the error of the data using the error correction code included in the data output by the RW unit 4. Do. Then, the data after error correction is output to the host side. Further, when the data output by the RW unit 4 is read, if the table conversion unit 22 outputs the erasure flag signal, the position of the erasure data indicated by the erasure flag signal and the error correction included in the read data are corrected. Data is corrected by so-called erasure correction (erasure correction) using the code, and the error-corrected data is output to the host side.

  Further, the error correction unit 23 outputs a correction end signal when the error correction processing is completed. If the error corrected symbols are consecutive, start information indicating the start position of the symbol sequence in which the error is corrected and continuous number information indicating the length of the symbol sequence in which the error is corrected are corrected. Output with end signal.

  Thus, according to the present embodiment, when reading from a sector in which a burst error has occurred, the table conversion unit 22 outputs an erasure flag signal, and the error correction unit 23 is recorded in the sector. Perform erasure correction on the data. As a result, the possibility of using alternative sectors is reduced by utilizing the ability of erasure correction.

  That is, in the present embodiment, as shown in FIG. 4, the control unit 5 receives the input of the sector number of the read destination and checks whether or not a burst error has occurred in the sector specified by the sector number ( If it occurs, the erasure correction mode is selected as the correction mode (S2). If not, the normal correction mode is selected as the correction mode (S3).

  Then, the control unit 5 instructs the head drive control unit 3 to move the head to the sector of the designated sector number, and receives the read data output from the RW unit 4 (read processing; S4). Here, the control unit 5 performs error correction on the read data in the correction mode selected in the processes S2 and S3 (S5). In other words, if a burst error has occurred in the sector from which data has been read, erasure correction using the past correction history is performed in addition to the error correction code. Otherwise, the error correction code is used. Normal error correction is performed.

  The control unit 5 checks whether or not a burst error has occurred from the result of the error correction processing here (S6), and if it has occurred, whether or not the number of symbols related to the burst error exceeds a predetermined threshold value. (S7). Here, if the number of symbols related to the burst error exceeds a predetermined threshold, the control unit 5 further controls the start position (start information) of the burst error and the number of symbols related to the burst error (continuous number information). It is checked whether or not has changed (S8). In other words, if the correction mode is the normal correction mode, it is a newly generated burst error, so in this process S8 it is determined that the start information and the continuous number information have changed. If the correction mode is the erasure correction mode, it is checked whether the start information and the continuous number information used in the erasure correction are different from the start information and the continuous number information newly detected in the process S5. Judge that it has changed.

  If it is determined in step S8 that the burst error start information and the continuous number information have changed, the control unit 5 updates the defect sector table and records new start information and continuous number information in the defect sector table. (S9).

  Then, the control unit 5 checks whether or not the reading of data from all the requested sectors has been completed (S10). If it has been completed, the process ends. If not, the sector number of the next sector is determined. The process is repeated from process S1.

  If it is determined in step S6 that no burst error has occurred, if the number of symbols related to the burst error does not exceed a predetermined threshold in step S7, and if a burst error occurs in step S8. When it is determined that the related start information or continuous number information has not changed, the process proceeds to step S10.

  As described above, in the present embodiment, in consideration of the possibility that a location where a burst error occurs (defect on the magnetic recording medium) grows, We are going to record further changes.

  According to the present embodiment, erasure correction is used as much as possible to correct errors, and the use of alternative sectors is not performed, thereby reducing the amount of use of alternative sectors and thus speeding up read processing. it can.

1 is a block diagram illustrating a configuration example of a magnetic disk device according to an embodiment of the present invention. 1 is a functional block diagram illustrating an example of a magnetic disk device according to an embodiment of the present invention. It is explanatory drawing showing the example of the defect sector table hold | maintained with the magnetic disc apparatus which concerns on embodiment of this invention. FIG. 6 is a flowchart showing an operation example of the magnetic disk device according to the embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Magnetic recording medium, 2 Head unit, 3 Head drive control part, 4 Read / write part, 5 Control part, 6 Storage part, 21 Defect sector table management part, 22 Table conversion part, 23 Error correction part

Claims (2)

A magnetic disk medium;
A reproducing unit for reproducing data from a signal recorded on the magnetic disk medium;
An error correction unit that corrects an error that may be included in the reproduced data; and a recording unit that records an occurrence position of the error corrected in the error correction unit;
Have
The error correction unit performs erasure correction processing on the reproduced data when a read position of the reproduced data is recorded as a continuous error occurrence position in the recording unit. A magnetic disk device. The magnetic disk device according to claim 1,
The number of locations where the error occurrence position recorded in the recording unit is continuous, or a change in at least one of the positions is detected, and when the change is detected, the error recorded in the recording unit A magnetic disk drive, further comprising a controller for updating information on the generation position.

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