KR100594303B1 - Method for controlling retry of hard disk drive and recording medium therefor - Google Patents

Abstract

The present invention relates to a retry control method for a hard disk drive, and more particularly, to a retry control method for compensating repeatable runout, and a recording medium suitable therefor.

The retry control method according to the present invention comprises the steps of: performing a first retry when a read error occurs; Storing the PES while following the track for the first retry; If the read error is not cured in the first retry, obtaining an RRO compensation value from the stored PES; And performing a second retry by applying the RRO compensation value.

According to the retry control method according to the present invention, if a read error occurs, the PES obtained during one revolution while performing the first retry is stored, and if the first retry fails, the RRO of the track having the error is stored based on the stored background. By obtaining a compensation value and applying the obtained RRO compensation value to perform retry again, the RRO may perform a compensated retry.

Description

Method for controlling retry of hard disk drive and recording medium therefor}

1 shows an example of servo information including RRO information.

2A and 2B show different magnetic recording heads, respectively.

3 is for showing that the offset occurs in accordance with the position on the disc in the magnetic recording head.

4 are waveforms showing the PES generated in the tracks.

5 is a flowchart illustrating a retry control method according to the present invention.

6 is a plan view of a configuration of a hard disk drive to which the present invention is applied.

7 is an electrical circuit diagram of a hard disk drive to which the adaptive retry control method according to the present invention is applied.

The present invention relates to a retry control method for a hard disk drive, and more particularly, to a retry control method for compensating repeatable runout, and a recording medium suitable therefor.

A hard disk drive, which is one of the data storage devices, plays back data recorded on the disk by the magnetic head or records user data on the disk.

On a hard disk drive, an error may occur during the data read operation. To remedy this, if an error occurs during read execution of data, a retry process is executed.

That is, when an error occurs during the read operation, the data read is repeatedly executed a maximum number of times while changing off-track read or data read related parameter values.

Known technical documents related to the present invention include Korea Patent Publication No. 2000-182292 and Japanese Patent Application Laid-open No. Hei 11-195211.

There are repeatable RunOut (RRO) components and Non-Repetitive RunOut (NRRO) components in following tracks of the hard disk drive. The RRO component can occur for disc warping, bending of the disk surface, placement of the disc relative to the spindle center, incomplete spindle motor bearings, or harmonics during rotation. The NRRO component can be caused by random perturbation and nutation due to bearing irregularities and the like.

The RRO component causes the track to deviate from the origin (the desired head trajectory) due to the above factors, and is repetitive with one fundamental frequency and several harmonics.

This repetitive RRO component is recorded in the servo information as information called RRO Correction Code (RCC) during the manufacturing process of the hard disk drive. Specifically, the RCC information is recorded in the RRO file after the burst. The recording of the RRO component in the servo information is disclosed in Korean Patent Laid-Open Publication No. 2003-48371 (published on June 19, 2003) filed by the present applicant.

When the hard disk drive records data, the RRO component is compensated and recorded using the RCC information included in the servo information.

However, since the RCC information is not available for reading the recorded data, the RRO component cannot be compensated for. As is well known, in the MR head, the recording head and the reading head exist separately, and the centers of the recording head and the reading head do not coincide with each other. This is called MR offset, and the MR offset separates the center of the recording head from the center of the reading head by a few tracks. Therefore, in the recording operation, the track on which data is recorded and the track tracked for recording data on the track are different from each other.

This MR offset becomes a factor in making it impossible to accurately compensate for the RRO component in reading the recorded data. Specifically, when reading a track on which data is recorded, the RRO applied in the recording operation, that is, the RRO of the track tracked by the read head when the data is recorded by the recording head, should be applied. However, when reading data, the read head only tracks the track on which the data is recorded, so that the RRO of the track tracked when the track is recorded cannot be known.

In addition, the distance between the center of the recording head and the reading head is also influenced by the skew angle depending on the position of the head. This skew angle, which depends on the position of the head, makes it more difficult to compensate for the RRO in the read operation.

To overcome this, a method of calculating the RRO compensation value in real time when reproducing the recorded data is used. U.S. Patent No. 6,097,565 (published on October 30, 2001), Korean Patent Publication No. 2004-97944 (published on November 18, 2004), 1997-78651 (published on December 12, 1997) and the like have a position error signal. A method for estimating and compensating for an RRO component is disclosed. However, because these techniques compensate for RROs based on PES made from tracks previously tracked by the read head, they are not accurate because they do not compensate for RROs based on PES made from tracks currently tracked by the read head. RRO compensation is difficult to achieve

Considering that the RRO varies between adjacent tracks, such as the RRO component caused by the fine curvature of the disc surface, it is necessary to compensate for the RRO based on the PES generated in the track currently being read.

An object of the present invention is to provide a retry control method capable of compensating RRO.

Another object of the present invention is to provide a computer-readable recording medium suitable for the retry control method described above.

Retry control method according to the present invention to achieve the above object

Performing a first retry when a read error occurs;

Storing the PES while following the track for the first retry;

If the read error is not cured in the first retry, obtaining an RRO compensation value from the stored PES; And

And performing a second retry by applying the RRO compensation value.

Here, the PES is stored in the volatile memory, and if the error is healed by the retry, it is preferable to further include the step of erasing the PES stored in the volatile memory.

A computer-readable recording medium according to the present invention for achieving the above another object is

In a recording medium that can be read by a computer on which a program for controlling the retry operation of a hard disk drive is recorded,

Performing a first retry when a read error occurs;

Storing the PES while following the track for the first retry;

If the read error is not cured in the first retry, obtaining an RRO compensation value from the stored PES; And

A program including a process of performing a second retry by applying the RRO compensation value is recorded.

The features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the invention shown in the accompanying drawings.

Reference will be made in detail to exemplary embodiments of the invention, wherein like reference numerals denote like elements. In addition, in order to simplify the description, anything that is not novel or well known to those skilled in the art will be omitted.

1 shows an example of servo information including RRO information.

Referring to FIG. 1, a servo feed 102 is inserted into each data feed 104. In the servo feed 102, a servo preamble, a servo address mark, gray codes and indexes, bursts A to D, and RRO are recorded.

The servo preamble is used for automatic gain control of servo circuits and phase synchronization of servo bit signals. The servo address mark occurs after the servo preamble and has a unique pattern with minimal detectability for the entire track. This servo address mark provides a basic timing reference for servo gray codes, indexes, bursts, and RROs. Gray codes and indexes may include track addresses, sector addresses, header numbers. Burst is for generating PES. Widely used is a four-burst (A-D) scheme that uses four bursts that are out of phase with one another in the radial direction. RRO is to compensate for the RRO component.

2A and 2B show different magnetic recording heads, respectively. 2A shows a case where the center of the recording head is different from that of the read head, and FIG. 2B shows a case where the center of the recording head and the center of the reading head are the same. In the magnetic recording head shown in Fig. 2A, it can be seen that there is an offset between the center of the recording head and the center of the read head.

3 is for showing that the offset occurs in accordance with the position on the disc in the magnetic recording head. The magnetic recording head is moved arcuately in the radial direction of the disc by the operation of the actuator arm. As a result, the center line of the magnetic recording head and the track center line on the disc do not coincide with each other. That is, skew and offset occur. Referring to Fig. 3, even when the read head is aligned with the track center line, it can be seen that the recording head is somewhat separated from the track center line, that is, the offset has occurred. The magnitude of this offset depends on the movement of the actuator arm, that is, the position of the magnetic recording head on the disc.

4 are waveforms showing the PES generated in the tracks. Referring to FIG. 4, there is a part where the PES changes rapidly, and it can be seen that such distortion occurs equally over several tracks. As such, the components that occur repeatedly in specific portions of the disc are referred to as RRO. Therefore, when reading data, the read performance can be improved by using the RRO compensation value calculated from previous tracks.

However, if a read error by the RRO occurs, that is, an error by the RRO that is not compensated by the RRO compensation value calculated in the previous tracks, it is necessary to compensate using the appropriate RRO for the track. Do. However, as shown in Figs. 2 and 3, the RRO applied when recording data on the corresponding track cannot be read due to the distance between the read head and the write head, MR offset, skew angle, and the like. Accordingly, it is desirable to calculate and use an RRO compensation value suitable for an error track.

5 is a flowchart illustrating a retry control method according to the present invention.

Read data (s502)

First, it is determined whether a read error has occurred (s504). If no read error has occurred, the process proceeds to step s502 and reads the next data.

If it is determined that a read error has occurred in step S504, the first retry is performed (s506).

When a read error occurs in a hard disk drive, the read parameters are read while the read parameters are changed, and the error is repaired. This is called a retry. At this time, the first retry process is performed without performing RRO compensation.

In this way, the PES is stored while following the corresponding track for the first retry (s508). The PES is stored in the volatile memory.

It is determined whether the error is cured by the first retry (s510).

If the error is cured in step s510, the process proceeds to step s502 to read the next data. If the error is not healed in step s510, the error is not caused by the read parameter but by the position of reading data, that is, the error by RRO.

If it is determined in step s510 that the error has not been healed, an RRO compensation value is obtained from the PES obtained in step s506. 12. 12 publication).

The second retry is performed by applying the obtained RRO compensation value (s514). In step s514, the data is read while the RRO is compensated based on the PES of the track in which the error occurs. It becomes possible.

It is determined whether the error is healed by the second retry (s516).

If the error is cured in step s516, the process proceeds to step s502 and the next data is read. If it is determined in step s516 that the error has not been healed, the error is not caused by a read parameter or an RRO error. Therefore, another retry operation may be performed or treated as an unrecoverable error (s518).

6 shows a configuration of a hard disk drive 10 to which the present invention is applied. The drive 10 includes at least one magnetic disk 12 that is rotated by a spindle motor 14. Hard disk drive 10 also includes a transducer 16 located adjacent disk surface 18.

The transducer 16 can read or write information on the rotating disk 12 by sensing and magnetizing the magnetic field of each disk 12. Typically each transducer 16 is associated with a respective disk surface 18. On the other hand, although shown and described as a single transducer 16 in FIG. 1, in practice this consists of a write transducer for magnetizing the disc 12 and a separate read transducer for sensing the magnetic field of the disc 12. It should be understood that there is. Typically, write converters consist of magnetic circuits with voids, and read converters consist of Magneto-Resistive (MR) elements. The transducer 16 is also commonly referred to as a head.

The transducer 16 can be integrated into the slider 20. The slider 20 is structured to create an air bearing between the transducer 16 and the disk surface 18. The slider 20 is coupled to the head gimbal assembly 22. The head gimbal assembly 22 is attached to an actuator arm 24 having a voice coil 26. The voice coil 26 is located adjacent to the magnetic assembly 28 that specifies the voice coil motor 30 (VCM). The current supplied to the voice coil 26 generates a torque that rotates the actuator arm 24 relative to the bearing assembly 32. Rotation of actuator arm 24 will move transducer 16 across disk surface 18.

The information is typically stored in concentric circular tracks on the disc 12. Each track 34 generally includes a plurality of sectors. Each sector includes a data field and an identification field (also called a servo field). The identification field consists of a gray code identifying the sector and the track (cylinder), and burst signals for detecting the extent to which the transducer 16 deviates from the track center. The transducer 16 is moved across the disk surface 18 by the movement of the actuator arm.

7 shows an electrical circuit of a hard disk drive to which the present invention is applied.

As shown in FIG. 7, the hard disk drive according to the present invention includes a disk 12, a converter 16, a preamplifier 210, a write / read channel 220, a host interface 230, and a controller 240. And a nonvolatile memory 250, a volatile memory 252, a temperature sensor 260, and a voice coil motor (VCM) driver 270.

The circuit configuration including the preamplifier 210 and the write / read channel 220 above will be referred to as a write / read circuit.

The nonvolatile memory 250 stores various programs and data for controlling the hard disk drive. In particular, the program is stored to execute the retry control method according to an exemplary embodiment of the present invention. In this case, the memory 250 is designed as a nonvolatile memory. On the other hand, the volatile memory 252 is provided to store the PES obtained during the retry process.

The retry table stores parameter values to ensure optimal performance of the hard disk drive.

First, the operation of a general hard disk drive will be described.

In the data read mode, the hard disk drive amplifies the electrical signal sensed by the converter 16 (also called a head) from the disk 12 in the preamplifier 210 to facilitate signal processing. Then, in the recording / reading channel 220, the amplified analog signal is encoded into a digital signal that can be read by a host device (not shown), converted into stream data, and transmitted to the host device through the host interface 230. send.

In contrast, in the data write mode, the hard disk drive receives data from a host device and temporarily stores the data in a buffer (not shown) embedded in the host interface 230, and sequentially outputs the data stored in the buffer. The write / amplify channel 220 converts the write current amplified by the preamplifier 210 to the disk 12 via the converter 16 after conversion to a binary data stream suitable for the write channel.

The controller 240 may be a digital signal processor (DSP), a microprocessor, a microcontroller, or the like. The controller 240 supplies a control signal to the write / read channel 220 to read from or write information to the disk 12. Information is typically sent from the R / W channel to the host interface circuit 2320. The host interface circuit 230 includes a buffer memory and control circuitry that allows a hard disk drive to interface to a system such as a personal computer.

The controller 240 is also coupled to the VCM drive circuit 270 which supplies a drive current to the voice coil 26. The controller 240 supplies a control signal to the VCM driving circuit 270 to control the excitation of the VCM and the movement of the transducer 16.

The controller 240 is coupled to a nonvolatile memory device 250 such as a flash memory device. The memory 250 stores instructions and data used by the controller 240 to execute software routines. One software routine is a seek routine that moves the transducer 16 from one track to another. The seek routine includes a server control routine to ensure that the transducer 16 is moved to the correct track.

When the retry mode is performed, the controller 240 resets the retry parameters related to the data read performance according to the retry number by using the retry table information stored in the memory 250 and repeatedly executes the data read. To control.

In particular, the controller 240 stores in the volatile memory 252 a PES obtained during one round while following a track in which an error occurs in order to read data again while performing a retry. After the disk is turned around, the controller 240 changes the read parameter to read data and determines whether the read data is in error. This process is repeated while resetting the read parameters.

If the first retry fails, the RRO compensation value is calculated from the PES stored in the volatile memory 252.

When performing the second retry, the controller 240 reads data by applying the calculated RRO compensation value.

In this way, in the second retry, the data is read in a state where the RRO is compensated, so that an error caused by the RRO can be healed.

If the second retry succeeds, the PES stored in the volatile memory 252 is erased. This is because the RRO may vary from zone to zone, so there is no need to reuse the previously calculated RRO compensation value.

The invention can be practiced as a method, apparatus, system, or the like. When implemented in software, the constituent means of the present invention are code segments that necessarily perform the necessary work. The program or code segments may be stored in a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network. Processor readable media includes any medium that can store or transmit information. Examples of processor-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memory, erasable ROM (EROM), floppy disks, optical disks, hard disks, optical fiber media, radio frequency (RF) networks, Etc. Computer data signals include any signal that can propagate over transmission media such as electronic network channels, optical fibers, air, electromagnetic fields, RF networks, and the like.

Specific embodiments shown and described in the accompanying drawings are only to be understood as an example of the present invention, not to limit the scope of the invention, but also within the scope of the technical spirit described in the present invention in the technical field to which the present invention belongs As various other changes may occur, it is obvious that the invention is not limited to the specific constructions and arrangements shown or described. That is, it is a matter of course that the present invention can be applied not only to various disk drives including hard disk drives, but also to various kinds of data storage devices.

As described above, according to the retry control method according to the present invention, if a read error occurs, the PES obtained during one revolution while performing the first retry is stored, and if the first retry fails, the error is stored based on the stored background. By obtaining the RRO compensation value for the generated track and applying the obtained RRO compensation value to perform the retry again, the RRO can perform the compensated retry.

Claims (3)

Performing a first retry when a read error occurs; Storing the PES while following the track for the first retry; If the read error is not cured in the first retry, obtaining an RRO compensation value from the stored PES; And And performing a second retry by applying the RRO compensation value. The method of claim 1, wherein the PES is stored in a volatile memory. And resetting the PES stored in the volatile memory when the error is healed by the retry. In a recording medium that can be read by a computer on which a program for controlling the retry operation of a hard disk drive is recorded, Performing a first retry when a read error occurs; Storing the PES while following the track for the first retry; If the read error is not cured in the first retry, obtaining an RRO compensation value from the stored PES; And And a program including a step of performing a second retry by applying the RRO compensation value.

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