JPH08203218A - Disk apparatus and error detecting correcting method for servo data in the apparatus - Google Patents

Abstract

PURPOSE: To detect and correct an error in servo data without a time delay when the servo data is read out. CONSTITUTION: Cylinder data CD, its vertical parity data CVP, horizontal parity CHP for the cylinder data CD and horizontal parity VHP for the vertical parity data CVP which are recorded in a servo region on a disk are extracted so as to be held in a register 192. After that, in a parity judgment circuit 193, a vertical parity check on the basis of the cylinder data CD and the verical parity data CVP, a horizontal parity check on the basis of the cylinder data CD and the horizontal parity CHP and a horizontal parity check on the basis of the vertical parity check CVP and the horizontal parity VHP are performed. In a CPU 20, which complement of the cylinder data CD and the vertical parity check CVP can be used as true cylinder data, is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk device for controlling the positioning of a head for recording / reproducing data at a target position on a recording medium on the basis of servo data including cylinder data recorded on the recording medium, and a device therefor. Servo data error detection / correction method

[0002]

2. Description of the Related Art In a disk device (data recording / reproducing device) typified by a hard disk device (HDD), data is written on the disk in order to know where the head is located on the disk which is a recording medium. It is common to calculate the position from the servo data. FIG. 7 shows a format example of a disk having such servo data.
Shown in

In a disk device, read / write data
When writing (recording / reproducing), the position is calculated from the servo data, the head is positioned at the target position (target cylinder) on the disk, and after this positioning is completed, data read or write is performed through the head. To do. Further, prior to the reading / writing of this data, the disk controller (HDC) reads the ID portion composed of the cylinder number and the head number written on the disk surface,
Make sure that it matches the target address (read / write address). After this confirmation, read or write operation is started.

As described above, in the conventional disk device, even if a servo data read error occurs, the ID section is read to confirm the cylinder number and the head number before actually performing the read / write operation. , Lead after this confirmation
Since it writes, there was little chance of making a mistake.

[0005]

As described above, in the conventional disk device, the influence on the read / write of the system due to the erroneous reading of the servo data is similar to that of the ID portion (servo data). It was kept small by providing redundancy.

On the other hand, in future disk devices,
It is expected that as the track density increases, the reproduction signal output of the servo data becomes smaller and the error probability increases.

On the other hand, recently, in order to efficiently use the disk area (improve the format efficiency), a disk format having no ID portion has been proposed. In this format, since there is no ID portion, it is very important to secure the reliability of servo data.

Conventionally, the servo data is provided with a parity, and it has been possible to detect the occurrence of an error in the servo data by using this parity.
Even if an error in the servo data is detected, since the disk format having the ID part has been conventionally applied, if the ID part is correct, it is possible to read or write.

On the other hand, when a new disk format having no ID portion is applied, if an error occurs in the servo data, at least one rotation wait occurs and the throughput decreases.

In order to prevent this inconvenience, it is necessary to provide a function of correcting an error when reading servo data. This error correction needs to be performed without delay when the servo data is read. If there is a time delay, it is necessary to provide a gap after the servo data, and the format efficiency is reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to perform error detection / correction of servo data without a time delay when the servo data is read, and a magnetic disk device and servo data of the same device. It is to provide an error detection / correction method.

[0012]

DISCLOSURE OF THE INVENTION A disk device according to the present invention is a positioning device for positioning and controlling a head for recording / reproducing data at a target position on a recording medium based on servo data including cylinder data recorded on the recording medium. Control means, cylinder data recorded in the servo area of the recording medium in which the servo data is recorded, vertical parity data composed of the same number of bits indicating the complement value of each bit of the cylinder data, and parity bits of the cylinder data. 1
Extraction means for extracting the second horizontal parity, which is the parity bit of the horizontal parity and the vertical parity data,
By inputting the cylinder data, the vertical parity data, the first horizontal parity and the second horizontal parity extracted by the extracting means, and comparing the cylinder data and the vertical parity data, it is possible to determine whether or not there is a vertical parity error.
When there is an error, it detects whether it is a 1-bit error or an error of 2 bits or more, detects the first horizontal parity error based on the cylinder data and the first horizontal parity, and detects the vertical parity data and Second
Parity determining means for detecting a second horizontal parity error based on the horizontal parity of the above, the positioning control means, based on the detection result of the parity error by the parity determining means, the extracted cylinder data or It is characterized in that which of the vertical parity data can be used as true cylinder data is determined, and the data determined to be usable is used for positioning control.

[0013]

In the above structure, in each servo area of the recording medium (that is, the disk), in addition to the cylinder data indicating the cylinder number (cylinder address), the same number of bits indicating the complementary value of each bit of the cylinder data. Of the vertical parity data, the first horizontal parity that is the parity bit of the cylinder data, and the second horizontal parity that is the parity bit of the vertical parity data are recorded.

The servo data recorded in the servo area is read by the head and converted into a digital amount (data pulse). The extracting means extracts cylinder data, vertical parity data, first horizontal parity, and second horizontal parity from this data pulse.

The parity determining means receives the cylinder data, the vertical parity data, the first horizontal parity and the second horizontal parity extracted by the extracting means, and compares the cylinder data and the vertical parity data to detect a vertical parity error. The detection is performed, and the first horizontal parity error based on the cylinder data and the first horizontal parity is detected, and the second horizontal parity error based on the vertical parity data and the second horizontal parity is detected. At this time, if a vertical parity error is detected, the parity determining means determines whether or not there is a 1-bit error (whether it is an error of 2 bits or more). This determination can be easily performed because each bit of the cylinder data is provided with the vertical parity indicating the complement value of the bit.

The positioning control means receives the detection result of the parity error by the parity determination means and determines whether cylinder data or vertical parity data can be used as true cylinder data.

When no error is detected by the parity judging means, or when the 1-bit error and the second horizontal parity error are detected but the first horizontal parity error is not detected, the cylinder data is Since it is correct, it is possible to use the cylinder data as true cylinder data.

When the 1-bit error and the first horizontal parity error are detected but the second horizontal parity error is not detected, the vertical parity data (which is the complement of cylinder data) is correct. Therefore, it is possible to use the complement of the vertical parity data as true cylinder data.

On the other hand, in the case of an error of 2 bits or more and in the case of a 1-bit error, if the first and second horizontal parity errors are both detected or not detected, the cylinder data is detected. Since an error has occurred in both the vertical parity data and the vertical parity data, or an error has occurred in either one of them, it is not possible to identify which of the errors has occurred, and therefore it is necessary to perform error processing.

Therefore, the positioning control means determines that the cylinder data is correct based on the detection result of the parity error by the parity determination means, and determines that the vertical parity data is correct for the cylinder data. , The complement of the vertical parity data is used as true cylinder data for the positioning control, and in other cases, error processing is performed.

As described above, in the above configuration, the parity check for each bit of cylinder data (vertical parity check) and the 1-bit horizontal parity added to each of the vertical parity data and the cylinder data for this vertical parity check. In the case of a 1-bit vertical parity error, it is possible to easily determine which of the cylinder data and the vertical parity data is correct only by the horizontal parity check using the. Therefore, when it is determined that the cylinder data is correct, the cylinder data can be used as it is. If it can be determined that the vertical parity data is correct, it can be used as true cylinder data simply by taking the complement of the vertical parity data, and the error bit position of the cylinder data is detected and corrected to the correct bit. Is equivalent to That is, in the above configuration, it is possible to substantially correct a 1-bit error without detecting the error bit position. From the above, it becomes possible to correct an error when reading servo data without a time delay, and it is possible to improve the reliability of servo control.

[0022]

Embodiments of the present invention will now be described with reference to a magnetic disk device (HDD).
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the magnetic disk device according to the embodiment.

The magnetic disk device shown in FIG. 1 is a medium for recording data, for example, a plurality of disks 11, and is used for writing data on the disks 11 (data recording) and reading data from the disks 11 (data reproduction). And the head 12 used. The head 12 is provided corresponding to each data surface of the disk 11.

The disk 11 is a spindle motor (SP
M) 13 rotates at high speed. The head 12 is attached to a head moving mechanism called a carriage 14, and the movement of the carriage 14 moves the head 12 in the radial direction of the disk 11. The carriage 14 includes a voice coil motor (V
CM) 15 is driven.

The spindle motor 13 and the voice coil motor 15 are connected to a motor driver IC 16. The motor driver IC 16 supplies a control current to the spindle motor 13 (hereinafter referred to as an SPM driver) 161 for supplying a control current to the spindle motor 13 to drive the motor 13 and a voice coil motor 15 to supply a control current to the motor 15. Voice coil motor driver (hereinafter referred to as VCM driver) 16 for driving
And 2. The value (control amount) of this control current is C
It is determined by calculation processing of the PU (microprocessor) 20 and given as an analog value.

The head 12 is connected to a head IC 17 mounted on a flexible printed wiring board (FPC), for example. The head IC 17 has a head amplifier 171 that amplifies the analog output read by the head 12.

The head IC 17 is a read / write IC 18
Connected with. The read / write IC 18 inputs the analog output (read signal of the head 12) amplified by the head amplifier 171 in the head IC 17, and performs signal processing necessary for data reproducing operation, for example, analog output to N
Signal processing for conversion into RZ data is performed. The read / write IC 18 also performs signal processing necessary for data recording operation, for example, data that modulates the NRZ data (write data) sent from the disk controller (HDC) 21 and writes it to the disk 11 (for example, 2-7, 1). -7
Signal processing for conversion into modulated data) is also performed.

The read / write IC 18 executes a normal recording / reproducing process of user data and a reproducing process of servo data necessary for a servo process for head positioning control.
The format of the disk 11 on which the servo data is recorded is shown in FIG.

First, each cylinder of the disk 11 is divided into a plurality of sectors. As shown in FIG. 2A, each sector is roughly divided into a servo area 111 for recording servo data and a user area 112 for recording user data. As shown in FIG. 2B, the servo area 111 is an AGC stabilizing area (amplitude AGC area) 11 in which data of a constant frequency is recorded so that the signal amplitude is stable.
1a, sector data area 11 in which sector data SD indicating erase and sector number (servo sector number) is recorded
1b, cylinder data area 111c in which cylinder data CD indicating the cylinder number (cylinder address) is recorded
And a burst area (burst position information area) 111d in which a burst signal (burst data) which is data for indicating the position information (positional error in the cylinder indicated by the cylinder data CD) by the waveform amplitude is recorded. The burst signal has position error signals A and B which are recorded at positions shifted by a half track with reference to the track center TC and have different phases.

At the beginning of the sector data SD, a pattern MK indicating the beginning of the data is added. In this embodiment, the sector data SD is composed of n bits and the cylinder data CD is composed of m bits.

Each bit of the cylinder data CD is Cm-1,
If Cm-2, ..., C0 (Cm-1 to C0 are "1" or "0"), the corresponding bits Cm-1, Cm-2 ,.
0 is the complementary value (level inversion value) Cm-1 ￣, Cm-2
, ..., C0 (where Cm-C0-indicates that they are the complements of Cm-C0) are added as vertical parity. This set of vertical parities Cm-C0- (vertical parity of m bits) is called vertical parity data CVP. The above is the same for the n-bit sector data SD, and the vertical parity data S is included in the sector data SD.
VP is attached.

The m-bit cylinder data CD has 1-bit horizontal parity (first horizontal parity) CHP.
Is added, and 1-bit horizontal parity (second horizontal parity) VHP is also added to the m-bit vertical parity data CVP of the data CD. Here, the horizontal parities CHP and VHP are the exclusive OR of the respective bits of the corresponding data CD and CVP. For example, the horizontal parity CHP is a value determined by CHP = ΣCi (1). However, ΣC i is from i = 1 to i =
It is shown that the exclusive OR of all Ci up to m-1 is taken. That is, CHP is a value obtained by CHP = C1 EXOR C2 EXOR ... EXOR Cm-2 EXOR Cm-1 (2), where "EXOR" is a symbol indicating an exclusive OR. Cylinder data CD
For the horizontal parity VHP of the vertical parity data CVP added to, the above Ci (i = 1 to m-1) is Ci.
You can replace it with ￣.

As shown in FIG. 3, the read / write IC 18 has an AGC amplifier 181, which has an AGC (Automatic Gain Control) function, a pulse generation circuit 182, and a peak hold circuit 183. Pulse generation circuit 182
Is a pulse peak detector (P) for discriminating read data and sync pulse from the read signal from the head 12.
PD) and outputs the data pulse including the cylinder data CD. The peak hold circuit 183 is used for the head 12
The peak of the read signal from is sample-held and the analog signal including the burst signal is output.

The read / write IC 18 is connected to a servo control circuit 19 which executes signal processing necessary for servo processing. The servo control circuit 19 has a decoding function of decoding the servo data to extract the cylinder data CD and the like, and an error detecting function of the cylinder data CD directly related to the present invention.

The servo control circuit 19, as shown in FIG.
From the data pulse output from the read / write IC 18, sector data S (with vertical parity data SVP)
D, cylinder data CD (with vertical parity data CVP) and decoder 191 for extracting 1-bit horizontal parity CHP, VHP, extracted sector data SD (with vertical parity data SVP), and vertical parity data CVP Register (shift register) 192 for holding cylinder data CD and horizontal parity CHP, VHP, and cylinder data based on cylinder data CD and horizontal parity CHP, VHP (with vertical parity data CVP) in register 192 CD
It has a parity judgment circuit 193 for making a true / false judgment, and a gray code conversion circuit 194. The Gray code conversion circuit 194 converts the cylinder data CD (with vertical parity data CVP) represented by a well-known Gray code into data represented by a normal numerical system. The register 192 is actually a first shift register that holds the n-bit sector data SD, the m-bit cylinder data CD and the 1-bit horizontal parity CHP, the n-bit vertical parity data SVP, the m-bit vertical parity data CVP, and 1-bit horizontal parity VHP
It is composed of two second shift registers for holding.

The CPU 20 is, for example, a one-chip microprocessor. The CPU 20 constitutes a servo processing system (head positioning control mechanism) for executing head positioning control together with the servo control circuit 19.
The cylinder data extracted by the servo control circuit 19 is read from the control circuit 19, the peak hold signal of the burst signal is read from the read / write IC 18, and the current position is calculated. In addition to head positioning control, the CPU 12 also controls read / write data transfer by controlling the disk controller 22.

The CPU 20 is an A / D converter (ADC) 20 for converting the peak hold signal of the burst signal read from the read / write IC 18 into a digital signal.
1 and a D / A converter (DAC) 2 for converting the control amount obtained by the servo processing (data representing the value of the current to be passed through the motors 13 and 15 by the motor driver IC 16) into analog data and outputting it to the motor driver IC 16.
02.

A non-volatile memory such as a ROM 21 is connected to the CPU 20. This ROM21 has C
The control program of PU20 is stored. The disk controller (HDC) 22 is a host device (not shown)
And a magnetic disk device, and mainly transfers read / write data. The disk controller 22 temporarily stores data (data read from the disk 11 and data to be written to the disk 11) transferred between the host device and the magnetic disk device by the disk controller 22. A buffer RAM 23 for connection is connected.

Next, the operation of the embodiment will be described. [Basic Operation] First, when the magnetic disk device configured as shown in FIG. 1 is powered on, the CPU 20 executes various initialization processing.

Next, the CPU 20 controls the SPM driver 161 of the driver IC 16 to activate the spindle motor 3 and start the rotational movement of the disk 11. Subsequently, the CPU 20 executes an initial seek operation. In this initial seek operation, the CPU 20 controls the VCM driver 162 of the motor driver IC 16 to perform servo processing for positioning the head 12 on the cylinder 0 which is the reference position on the disk 11.

When an access request is issued from the host device, the CPU 20 moves the head 12 onto the target cylinder corresponding to the logical address to be accessed and executes the read / write operation. That is, the CPU 20 executes the speed control to move the head 12 to the target cylinder. The CPU 20 continuously executes the position control to position the head 12 at the track center of the target cylinder.

When the positioning control of the head 12 is completed,
Read / write operation is executed. In this read / write operation, the CPU 12 and the HDC 15 execute read / write data transfer control.

That is, in the read operation, the read / write I
The C18 reproduces read data from the read signal read from the designated sector of the target cylinder by the head 12 and transfers it to the disk controller 22 (serial transfer).
To do. The disk controller 22 temporarily stores the read data in sector units in the buffer RAM 23, and transfers the read data for the sectors corresponding to the logical address to be accessed to the host device.

On the other hand, in the write operation, the disk controller 22 temporarily stores the write data transferred from the host device in the buffer RAM 23, and sequentially transfers the write data in sector units to the read / write IC 18. The read / write IC 18 converts the write data into a write current and supplies it to the head 12 via the head IC 17. The head 12 converts the write current into a recording magnetic field and records it in the user area 220 (see FIG. 2A) of the designated sector of the target cylinder. [Speed Control Operation] Next, the speed control operation of the head positioning control in the above basic operation will be described.

First, the analog output read from the disk 11 by the head 12 is amplified by the head IC 17 and supplied to the read / write IC 18, and separated into two signals in the read / write IC 18 as described below. .

That is, in the read / write IC 18, the analog output (read signal from the head 12) amplified by the head IC 17 and further amplified by the AGC amplifier 181.
From the above, the data pulse including the cylinder data CD is extracted by the pulse peak detection of the pulse peak detector (PPD) included in the pulse generation circuit 182. Further, the peak hold circuit 183 holds (peak-holds) the amplitude of the burst signal (position error signals A and B forming the position information) included in the analog output, and extracts the amplitude from the analog output.

FIG. 4 shows the 1-bit structure of the cylinder data CD. As shown in the figure, the analog waveform (analog output) of the cylinder data CD portion with the vertical parity data CVP in the servo data (read by the head 12) is a positive waveform with respect to the waveform portion for the clock C for one bit of data. It consists of a waveform portion for data PD and a waveform portion for negative data ND. In the example of the cylinder data CD, the positive data PD constitutes 1 bit Ci (i = 0 to m-1) in the cylinder data CD, and the negative data ND corresponds to the positive data PD (bit in the cylinder data CD). It forms the vertical parity (complement Ci). this is,
The same applies to the sector data SD with vertical parity data SVP in the servo data, and the positive data PD is
1 bit in the sector data SD, negative data N
D forms a vertical parity (complement) of the positive data PD (bits in the sector data SD). The same applies to the horizontal parities CHP and VHP in the servo data, and the positive data PD is the horizontal parity CHP (cylinder data CD).
Of the vertical parity data CVP added to the cylinder data CD, and the negative data ND forms the horizontal parity VHP.

From the above, the data pulse extracted by the pulse generation circuit 182 in the read / write IC 18 is
As shown in FIG. 4, it includes a clock C, positive data PD and negative data ND.

Decoder 191 in servo control circuit 19
Is a pulse generation circuit 182 in the read / write IC 18.
The data pulse extracted by is input, and as shown in FIG. 4, the window for extracting the positive data PD (the positive data window) causes the sector data S consisting of the positive data PD to be input.
D, cylinder data CD and (for cylinder data CD)
The horizontal parity CHP is extracted, and the window for extracting the negative data ND (negative data window) is used to form the vertical parity data SVP (for the sector data SD), the vertical parity data CVP (for the cylinder data CD) and the negative parity data CVP (for the sector data SD). Vertical parity data (for CVP) Horizontal parity VHP is extracted.

The clock C is used as a signal for generating the positive data window and the negative data window (synchronization window) and is always "1". On the other hand, the positive data PD and the negative data ND are "1" or "0". Particularly for the cylinder data CD with the vertical parity data CVP and the sector data SD with the vertical parity data SVP, the negative data ND paired with the positive data PD is "when normal" PD is "1". When it is "0" and PD is "0", it is "1".

The sector data SD, the cylinder data CD, and the horizontal parity CHP (for the cylinder data CD), the vertical parity data SVP (for the sector data SD), and the vertical parity (for the cylinder data CD) extracted by the decoder 191 in this way are provided. The parity data CVP and the horizontal parity VHP (for vertical parity data CVP) are serially input to the register (shift register) 192 in synchronization with the clock extracted by the decoder 191.
It is held in the register 192.

Then, the parity determination circuit 193 in the servo control circuit 19 determines whether the data SD is true or false by a vertical parity check based on the sector data SD with vertical parity data SVP in the register 192. Since the determination of authenticity of the sector data SD is not directly related to the present invention, its explanation is omitted.

At the same time, the parity judgment circuit 193 determines the cylinder data CD based on the cylinder data CD with the vertical parity data CVP and the horizontal parities CHP and VHP.
(Furthermore, the authenticity of the vertical parity data CVP) is determined. This true / false determination is performed by the vertical parity check using the vertical parity data CVP, the horizontal parity CHP,
The horizontal parity check using VHP is performed as follows.

First, in the vertical parity check, the complement (level) of each bit of m-bit cylinder data CD (positive data PD) and each bit of m-bit vertical parity data CVP (for cylinder data CD) (negative data ND) is calculated. (Inverted bit) and each corresponding bit. In this vertical parity check, the presence of vertical parity error is detected by detecting the bits whose logical values do not match. Although this vertical parity check can detect at which bit position the cylinder data CD or the vertical parity data CVP has an error,
It cannot be detected which side of the cylinder data CD and the vertical parity data CVP has an error. However, in this embodiment, it is not necessary to detect an error bit position (a bit position where the values do not match), and it is simply determined whether there is a vertical parity error (whether there is a mismatched bit),
If there is an error, it is only necessary to detect whether it is a 1-bit error (whether it is an error of 2 bits or more).

Next, the horizontal parity check is performed for each of the cylinder data CD and the vertical parity data CVP by using the horizontal parities CHP and VHP attached to the data CD and CVP. That is, in the horizontal parity check of the cylinder data CD, the horizontal parity is obtained by performing the exclusive OR operation of the equation (2) using each bit of the cylinder data CD, and the horizontal parity is added to this and the cylinder data CD. This is performed by comparing the horizontal parity CHP (for cylinder data CD) that has been generated, and the horizontal parity error (horizontal parity NG, first horizontal parity error) is detected by detecting the mismatch. Similarly, the horizontal parity check of the vertical parity data CVP (for cylinder data CD) is performed by performing the exclusive OR operation similar to the equation (2) using each bit of the vertical parity data CVP. And the horizontal parity VHP (for vertical parity data CVP) attached to this and the vertical parity data CVP.
Is done by comparing and, by detecting the mismatch,
A horizontal parity error (horizontal parity NG, second horizontal parity error) is detected.

Now, the regenerated cylinder data CD held in the register 192 and its vertical parity data CV.
It is assumed that P and horizontal parities CHP and VHP added to the data CD and CVP are as shown in FIG. 5 (when m = 6). That is, the reproduced 6-bit cylinder data CD (C5 C4 C3 C2
C1 C0) is "010001", the horizontal parity CHP added to the cylinder data CD is "0", and the reproduced 6-bit vertical parity data CVP.
(C5 C4 C3 C2 C1 C0) is "101100",
It is assumed that the horizontal parity VHP added to the vertical parity data CVP is "0".

In this case, the cylinder data CD is "010
001 ", the vertical parity data CVP
Is "010011", and the value of bit C1 does not match, it can be seen that an error (vertical parity error) has occurred in bit C1. However, in this embodiment, as described above, it is detected only as a 1-bit error.

Further, when the horizontal parity is calculated from the reproduced 6-bit cylinder data CD "010001", "0" is obtained. Since this value matches the horizontal parity CHP, the horizontal parity error for the cylinder data CD is obtained. It is determined that there is no. On the other hand, the reproduced 6-bit vertical parity data CVP “1011”
When the horizontal parity is calculated from "00""," 1 "is obtained. Since this value does not match the horizontal parity VHP, it is determined that the vertical parity data CVP has a horizontal parity error.

As a result of the above parity check, the parity judgment circuit 193 determines whether or not there is a vertical parity error, and if there is a vertical parity error, whether it is a 1-bit error (whether it is an error of 2 bits or more). , A parity determination result which does not show information indicating the presence / absence of a horizontal parity error (first horizontal parity error) for the cylinder data CD and the presence / absence of a horizontal parity error (second horizontal parity error) for the vertical parity data CVP. Set in register.

The CPU 20 reads the judgment result of the parity judgment circuit 193 from the parity judgment result register. Then, based on the read determination result of the parity determination circuit 193, the CPU 20 (1) if there is no error,
That is, if there is no vertical parity error, first horizontal parity error, or second horizontal parity error,
(2) There is a 1-bit vertical parity error (1-bit error) and a second horizontal parity error, and when there is no first horizontal parity error, (3) a 1-bit vertical parity error (1-bit error) If there is a first horizontal parity error and there is no second horizontal parity error,
(4) It is determined which of the cases other than (1) to (3) above applies. Here, the specific content in the case of (4) above is that although there is no vertical parity error, if at least one of the first horizontal parity error and the second horizontal parity error is present, a 1-bit vertical parity error ( 1-bit error) and first and second horizontal parity errors, 1-bit vertical parity error (1-bit error) and no first and second horizontal parity errors, or 2 This is a case where there is a vertical parity error of 2 bits or more (error of 2 bits or more).

When the CPU 20 determines which of the above conditions (1) to (4) is satisfied based on the determination result of the parity determination circuit 193, the following will be described based on the determination result. It is determined whether the cylinder data CD or the vertical parity data CVP is correct, or neither of them is correct.

First, when the above condition (1) is satisfied, the CPU 20 determines that the cylinder data CD is correct, and determines to use the data CD as true cylinder data.

Even when the condition (2) is satisfied, the CPU 20 determines that the cylinder data CD is correct and determines to use the data CD as true cylinder data. In the case of the example of FIG. 5 described above,
Cylinder data CD as it meets the condition of (2)
Is determined to be the true cylinder data.

When the condition (3) is satisfied, the CPU 20 determines that the vertical parity data is correct, and uses the complement of the data (level inversion data of each bit) as the true cylinder data. Decide that.

If the condition (4) is satisfied, the CPU 20 determines that neither the cylinder data CD nor the vertical parity data is correct, or determines which is correct, and does not use the cylinder data. It is decided to perform error processing such as controlling with.
In this error processing, the write operation is stopped if it is being written.

FIG. 6 shows the logic of the above judgment in the CPU 20. The CPU 20 reads from the servo control circuit 19 the cylinder CD with vertical parity data CVP (converted by the Gray code conversion circuit 194 into normal numerical value system data) and the sector data SD held in the register 192. When the CPU 20 determines that the condition (1) or (2) is satisfied based on the determination result of the parity determination circuit 193, the cylinder data CD read from the servo control circuit 19 is used as it is as the true cylinder. Select as data to determine if the head 12 is currently on the correct cylinder. Similarly, when the CPU 20 determines based on the determination result of the parity determination circuit 193 that the above condition (3) is satisfied, the complement of the vertical parity data CVP read from the servo control circuit 19 (level of each bit) Whether the head 12 is currently on the correct cylinder by selecting (reversed data) as the true cylinder data, that is, using the complement of the vertical parity data CVP as the corrected correct data of the erroneous cylinder data CD. To judge.

During speed control, the CPU 20 reads the cylinder data CD (hereinafter referred to as CDx) read at the position of the preceding sector (servo sector) and the cylinder data CD read from the current sector (hereinafter, referred to as CDx). The moving speed V of the head 12 is calculated from the following expression V = (CDx-CDy) / sector time. Here, the sector time is the time required to rotate (rotate) the disk 11 for one sector. Also,
CDx and CDy are not necessarily the cylinder data CD in the servo data, and when the condition (3) is satisfied as described above, they are the complements of the vertical parity data CVP attached to the cylinder data CD. is there.

Further, the CPU 20 has the cylinder data CD or the vertical parity data C obtained from the servo control circuit 19.
The moving distance from the current position obtained from the complement of VP (selected cylinder data) to the target cylinder is calculated, and the target speed of the head 12 is determined from the moving distance. This target speed is determined by referring to a target speed table prepared in advance in the ROM 21, for example.

The CPU 20 determines the amount of current flowing through the voice coil motor 15 by taking the difference between the moving speed V and the target speed. Then, the CPU 20 converts the determined current amount (digital control amount) into an analog control amount (analog voltage) by the D / A converter 202, and the motor driver IC 1
Give to 6. The VCM driver 162 in the motor driver IC 16 is controlled by the CPU 20 (D / A converter 202).
(Through) the applied analog voltage is converted into a corresponding current (control current) and supplied to the voice coil motor 15. When a current flows through the voice coil motor 15, a force proportional to the amount of the current is generated, and the carriage 14 moves.

In this way, the CPU 20 executes feedback control for driving and controlling the voice coil motor 15 so that the error between the target speed and the moving speed V becomes zero. [Position Control Operation] Next, the position control operation of the head positioning control in the above-described basic operation will be described.

First, the CPU 20 obtains the cylinder data CD (or the complement of the vertical parity data CVP used as the true cylinder data) from the servo control circuit 19 and extracts it by the peak hold circuit 183 in the read / write IC 18 as described above. A peak hold signal of the amplitude of the generated burst signal (position error signals A and B forming the burst signal) is obtained through the A / D converter 201. That is, CPU2
In addition to the cylinder data CD (or the complement of the vertical parity data CVP), 0 represents the amplitude of the burst signal (which constitutes the position error signals A and B) peak-held by the peak-hold circuit 183 in the read / write IC 18 as A. /
Obtain D (analog / digital) converted data (digital burst data BSTA, BSTB).

Based on the obtained burst data (BSTA, BSTB), the CPU 20 calculates the position error BSTREF of the target cylinder of the head 12 by the following equation: BSTREF = (BSTA-BSTB) / (BSTA +
BSTB).

The CPU 20 then calculates the position error B
Digital filter arithmetic processing for phase compensation for STREF is executed. Specifically, the CPU 20
Is the calculated position error BSTREF and BSTREF and 1 before 1 to N samples, for example, 1 to 3 samples before.
Up to 3 samples before, using the output value (control amount), B
Digital filter arithmetic processing for performing phase compensation for STREF is performed by the following equation: y (i) = [b (i) x (i) + b (i + 1) x (i +
1) + b (i + 2) x (i + 2) + b (i + 3) x (i
+3)]-[a (i + 1) y (i + 1) + a (i + 2)
y (i + 2) + a (i + 3) y (i + 3)]. Where y (i) is the output value before i samples, x (i) is the position error BSTREF before i samples,
a (i) and b (i) are parameter values of the digital filter.

Next, the CPU 20 calculates the calculated position error BS.
The VCM driver 16 is controlled by determining the control amount (digital control amount) obtained by TREF and the filter calculation process, converting the control amount into the analog control amount (analog voltage) by the D / A converter 202, and applying the converted amount to the motor driver IC 16.
Control 2 The VCM driver 162 is a current (control current) corresponding to the analog voltage given from the CPU 20.
Is converted into the voice coil motor 15 and is supplied to the voice coil motor 15.

In this way, the CPU 20 controls the head 12
So that the position error with respect to the track center of
Feedback control for driving and controlling the voice coil motor 15 is executed.

In the above embodiment, the processing corresponding to the error correction has been described as being performed by the CPU 20, but the parity determination circuit 193 in the servo control circuit 19 is used as true serial data. The data used (cylinder data CD or the complement of vertical parity data CVP) is sent to the CPU 2 via a register, for example.
It may be passed to 0.

Further, in the above embodiment, the sector data SD
With respect to the above, the horizontal parity is not added, but by adding the horizontal parity to each of the sector data SD and its vertical parity data SVP, an error correction similar to that of the cylinder data CD may be possible.
In addition, the sector data SD and the cylinder data CD, and the vertical parity data SVP and the vertical parity data CVP are collected as one unit, and horizontal parity is added to each of the units, and error detection is performed in that unit.
It is also possible to make corrections. Further, in the above embodiment,
Although the case where the even parity is used as the horizontal parity has been described, the odd parity may be used.

[0078]

As described above in detail, according to the present invention, error correction and error detection capability can be improved when a cylinder data reading error occurs due to servo data having a lowered signal level, and error detection processing can be performed. Not only that, processing corresponding to error correction can be performed without delay when the data is read. Therefore, the reliability of servo control can be improved, and even if a new disk format having no ID section is applied, the throughput is not reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a disk format applied in the embodiment.

FIG. 3 is a block diagram showing a main configuration of a read / write IC 18 and a servo control circuit 19 in FIG.

FIG. 4 is a diagram showing a 1-bit configuration of cylinder data CD included in servo data in association with an analog waveform.

FIG. 5 is a diagram showing an example of extracted cylinder data CD, its vertical parity data CVP, and horizontal parities CHP and VHP added to both of the data.

FIG. 6 is a diagram showing an error correction logic according to a determination result of a parity determination circuit 193.

FIG. 7 is a diagram showing a conventional disc format.

[Explanation of symbols]

11 ... Disk (recording medium), 12 ... Head, 13 ... Spindle motor (SPM), 14 ... Carriage, 15 ...
Voice coil motor (VCM), 16 ... Motor driver IC, 17 ... Head IC, 18 ... Read / write IC,
19 ... Servo control circuit (extracting means, positioning control means), 20 ... CPU (positioning control means), 21 ... RO
M, 22 ... Disk controller (HDC), 23 ... Buffer RAM, 182 ... Pulse generation circuit, 183 ... Peak hold circuit, 191 ... Decoder (extracting means), 19
2 ... Register, 193 ... Parity judgment circuit.

Claims (5)

[Claims] 1. A positioning control means for positioning and controlling a head for recording and reproducing data to a target position of the recording medium based on servo data including cylinder data recorded on the recording medium, and the servo data is recorded. The cylinder data recorded in the servo area of the recording medium, vertical parity data composed of the same number of bits indicating a complement value of each bit of the cylinder data, first horizontal parity that is a parity bit of the cylinder data, and the Extracting means for extracting a second horizontal parity, which is a parity bit of the vertical parity data, and the cylinder data, the vertical parity data, the first horizontal parity and the second horizontal parity extracted by the extracting means. Input and compare the cylinder data and the vertical parity data. And whether or not there is a vertical parity error, and if there is an error, it is detected whether it is a 1-bit error or an error of 2 bits or more, and the first horizontal based on the cylinder data and the first horizontal parity. A parity determination unit that detects a parity error and a second horizontal parity error based on the vertical parity data and the second horizontal parity; and the positioning control unit includes the parity error by the parity determination unit. Based on the detection result of, it is determined which of the complement of the cylinder data or the vertical parity data can be used as the true cylinder data, and the data judged to be usable is used for the positioning control. Disk device. 2. The positioning control means detects the cylinder data when no error is detected by the parity determining means and when only the 1-bit error and the second horizontal parity error are detected. , The above 1
When only a bit error and the first horizontal parity error are detected, it is determined that the complement of the vertical parity data can be used as the true cylinder data, and a predetermined error otherwise. The disk device according to claim 1, wherein processing is performed. 3. A servo data error detection / correction method in a disk device for controlling the positioning of a head for recording / reproducing data at a target position of the recording medium based on servo data containing cylinder data recorded on the recording medium. In each servo area of the recording medium in which the servo data including the cylinder data is recorded, vertical parity data composed of the same number of bits indicating the complementary value of each bit of the cylinder data, and parity bits of the cylinder data. A certain first horizontal parity and a second horizontal parity that is a parity bit of the vertical parity data are recorded respectively, and the cylinder data and the vertical data recorded in the servo area of the recording medium are recorded during the positioning control. Parity data, the first horizontal parity and the second horizontal parity Verticality by extracting the cylinder data, inputting the extracted cylinder data, the vertical parity data, the first horizontal parity, and the second horizontal parity, and comparing the cylinder data and the vertical parity data. Whether or not there is an error, and if there is an error, it is detected whether it is a 1-bit error or an error of 2 bits or more, and a first horizontal parity error is detected based on the cylinder data and the first horizontal parity. And a second horizontal parity error based on the vertical parity data and the second horizontal parity is detected. Based on the error detection result, either the cylinder data or the complement of the vertical parity data is a true cylinder. It is judged whether it can be used as data, and if the data is judged to be usable, the positioning control Servo data error detection in a disk device characterized by being used
Correction method. 4. A case in which none of the vertical parity error, the first horizontal parity error, and the second horizontal parity error is detected, and only the 1-bit error and the second horizontal parity error are detected. If the 1-bit error and the first horizontal parity error are detected, then the complement of the vertical parity data can be used as the true cylinder data. 4. A method for detecting and correcting an error in servo data in a disk device according to claim 3, wherein the predetermined error processing is performed in other cases. 5. A recording medium for a disk device, in which servo areas in which servo data including cylinder data used for head positioning control are recorded are radially arranged, wherein the cylinder data is provided in each servo area of the recording medium. In addition, vertical parity data composed of the same number of bits indicating the complement value of each bit of the cylinder data, a first horizontal parity that is the parity bit of the cylinder data, and a second parity bit of the vertical parity data.
The horizontal parity of each is recorded, and during the positioning control, the cylinder data, the vertical parity data, the first horizontal parity, and the second horizontal parity recorded in the servo area are extracted. Detection of vertical parity error based on cylinder data and the vertical parity data, detection of first horizontal parity error based on the cylinder data and the first horizontal parity, and detection of the vertical parity data and the second horizontal parity A recording medium for a disk device, which is capable of detecting a second horizontal parity error.