JPH0831103A - Data recording and reproducing device and method for processing servo applied to same - Google Patents

Abstract

PURPOSE:To correctly detect a top position of a data sector without providing a specific area recording an address mark on a disk and even when no servo sector pulses are generated continuously to correctly detect it even when no data sector position detection detects servo code information correctly. CONSTITUTION:A servo processing circuit 11 extracts a servo sector number recorded on each servo area on the disk 1. Then, a CPU 12 discriminates whether or not the servo sector number is the one extracted correctly when not seek operating, and estimates the correct servo sector number to be obtained essentially based on the servo sector number obtained the last time when not correct, and obtains the data sector generating timing data based on the correctly extracted or estimated servo sector number, and generates the corresponding data sector pulse by setting them to a data sector pulse generation circuit 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard disk device for positioning and controlling a head for recording / reproducing data at a designated position on a disk based on servo data recorded in each servo area set on the disk. The present invention relates to a data recording / reproducing apparatus such as the above, and more particularly to a data recording / reproducing apparatus of a method of accessing a disk in sector units and a servo processing method applied to the same.

[0002]

As is well known, a hard disk drive (H
DD) is a data recording / reproducing apparatus in which data is recorded / reproduced by a head on the surface of a disk 1 which is a recording medium as shown in FIG. As shown in FIG. 16, a large number of tracks are formed in the disk 1 in the radial direction, and each track is divided into a plurality of sectors DS. Normally, the disk 1 used for the HDD uses one side or both sides of a plurality of sheets as the data side, and therefore the tracks are handled by the concept that tracks in the same axial direction are called cylinders. Therefore, each track is referred to as a cylinder CL here.

Each sector DS is roughly divided into a header portion 1a including an ID area and a user data area 1b. Further, in the sector servo type HDD, a servo area SA in which servo data is recorded is provided at the beginning of the sector DS. The servo area SA is radially recorded on the disk 1 for each sector DS of all cylinders CL.

The servo area SA is data used for head positioning control, and as shown in FIG. 14, a cylinder code area (cylinder address code area) 1
3e and burst pattern area 13g. HDD
The servo system executes the speed control for moving the head to the target cylinder based on the cylinder address (cylinder address code) reproduced from the cylinder code area 13e by the head. When the head reaches the target cylinder, the burst pattern area 13g
Position control for positioning the head at the center of the target cylinder is executed based on the burst data (position signal) reproduced from.

In addition to this, the servo area SA is shown in FIG.
As shown in, AGC area 13a, erase area 1
3b, 13i, reference signal areas 13c, 13f, 13
h, and sector / index pattern area 13
have d. Sector / index pattern area 1
3d is an area in which a signal pattern for generating the servo sector pulse SSP or the servo index pulse SIP is recorded. The servo sector pulse SSP is a pulse output for each servo area SA. Also,
The servo index pulse SIP is a pulse serving as a reference point of the cylinder CL, and is a pulse output only at a specific position.

The ID area of the sector DS is, as shown in FIG. 15, a PLL / SYNC area 14a, a SYNC byte area 14b, a cylinder accord (upper byte) area 14c, and a cylinder code (lower byte) area 14.
d, head number area 14e, sector number area 14
f, a flag byte area 14g and a CRC byte area 14h.

The PLL / SYNC area 14a is an area for synchronizing the data discrimination window before reading the header portion 1a, and records a synchronization pattern of a predetermined frequency. SYNC byte area 14b
Stores information necessary for synchronization for demodulating the input NRZ (Non Return to Zero) code signal in byte units by synchronizing in the PLL / SYNC area 14a. In the HDD, the read data reproduced by the head is converted into NRZ code.

The cylinder code area is an area in which a cylinder address code (cylinder number) corresponding to the sector DS is recorded. The upper 8 bits of the upper byte area 14c and the lower 8 bits of the lower byte area 14d are recorded.
Recording a bit. The head number area 14e records the head number (byte) selected when accessing the sector DS. Sector number area 14f
Is the sector number (byte) for identifying the sector DS
Is recorded. The flag byte area 14g is an area for recording flag information and the like when a failure occurs in the data area 1b of the sector DS. CRC byte area 1
4h is a CRC (Cyclic Red) for verifying whether the contents are normal when the cylinder address code, head number, sector number and flag information are read.
undancy Check) This is an area for recording a code (byte).

By the way, in recent years, in order to increase the recording density of data, CDR (Constant Density Recordin)
HDD of type g) has been developed. In this CDR system, as shown in FIG. 13, the disk 1 is radially divided into a plurality of zones (here, three zones Z1 to Z3),
Each zone contains tens to hundreds of cylinders (tracks).

The CDR system has a sector structure in which the physical circumference of a cylinder is assumed and the recording density for the circumference is made substantially constant. That is, the number of data sectors is different for each zone. As a specific example, as shown in FIG. 13, the outermost zone Z1 has a sector configuration of sector numbers 0 to 9, and the innermost zone Z3.
Is a sector configuration of sector numbers 0 to 5. Also, CDR
In the method, the data transfer rate is different for each zone.

In the CDR system, the servo area S
A is radially recorded on the disk 1 over each zone. Therefore, the servo area SA is not necessarily located at the head of each sector. In other words, the servo sector based on the servo area SA is configured to include the immediately following data sector and a part of the data sectors continuous with the immediately following data sector. Also, the ID area of each sector is arranged differently for each zone.

In the HDD, when the head is positioned at the target cylinder based on the servo data, a read operation for reading the ID information of the sector is executed in order to access the designated sector. In this reading operation, when the read signal from the head detects a predetermined voltage within a certain period of time, it is determined that the information "1" has been read.

Specifically, as shown in FIG.
A read signal that exceeds a predetermined slice level for a certain period of time is detected as information "1". At this time, if the data discrimination window is synchronized with the magnetic recording on the disk 1, normal information can be detected from the read signal. However, as shown in FIG. 12B, if the data discrimination window is not synchronized with the magnetic recording on the disk 1, erroneous information will be detected for the same read signal. In order to synchronize such a data discrimination window with magnetic recording, as shown in FIG.
A PLL / SYNC area 14a is provided.

Further, in the servo area SA, servo data as shown in FIG. 14 is recorded. For each cylinder, as shown in FIG. 11, a cylinder address code or burst data is recorded as a magnetic pattern. ing.

In the above-mentioned CDR type HDD, as shown in FIG. 10, there are cases where a plurality of data sectors exist between the servo areas SA and one data sector has only a part of the data area. HDD is servo area S
The servo sector pulse SSP (or the servo index pulse SIP) is output at the timing A, and the data sector pulse DS is output at the timing of the ID area of the data sector.
Output P.

In the HDD, as shown in FIG. 14, the gain of the circuit is adjusted in the AGC area 13a of the servo area so that the amplitude of the output signal is adjusted to be constant. After that, the erase area 13b is detected and then the reference signal area 13c is detected, and the preparation for reading the servo data is completed. The read start position of the servo data is a position called a start bit immediately after the reference signal area 13c. The start bit synchronizes the circuit, and the sector / index pattern area 13 is continuous with this.
The servo sector pulse SSP or the servo index pulse SIP is output according to the pattern of d.

The cylinder address code (cylinder code) is usually recorded by an encoding method called a gray code. The Gray code is a binary code in which, when a continuous numerical value is expressed in a binary number, adjacent numerical values are different from each other by only 1 bit. Specifically, for example, the decimal number “6, 7,
8 ”is the gray code“ 00101,00100,011
00 ”. As a general expression, the i-th bit Gi of the Gray code is "Gi = Bi XOR Bi + 1". Bi and Bi + 1 are i-th and i + 1-th bits when a decimal number is converted into a binary number. XOR is a symbol indicating an exclusive OR operation.

By using such a gray code, the cylinder address code is accessed when the head is moved to the target cylinder, but the deviation of the read data can be kept within one cylinder.
As a specific example, as shown in FIG. 9, when the head crosses the cylinder "n + 2" to the cylinder "n + 1", the same cylinder address code as when the head is located on the cylinder n is read.

In FIG. 9A, the cylinder address code is recorded in the cylinder code area 13e as a gray code. Further, in the burst area 13g, a position signal (burst data) for detecting a position shift amount with respect to the center of the target cylinder based on the amplitude of the output signal is recorded. FIG. 7B shows the actual recording state of the cylinder address code converted into the Gray code, and a signal was output in the area of the next data discrimination window after the clock bit (CLK) was generated. In this case, it indicates that the information is recognized as information "1". Further, it is indicated that no signal is output in the area of the next data discrimination window, and when the signal is output in the area next to the window, the information is recognized as information "0".

[0020]

As mentioned above, the CDR
In the conventional HDD including the system, the ID information in the ID area is first referred to when the specified data is accessed from the disk 1. When it is recognized from the ID information that the sector is an access target, an access to a data area continuous to the ID area is executed.
At this time, the ID information in the ID area cannot be read unless the access is made from the head position of the ID area. As shown in FIG. 15, when access is started from the cylinder code area 14c, for example, PLL / SY
Since the circuit on the NC area 14a cannot be synchronized, the data discrimination window and the magnetic recording cannot be synchronized.

Therefore, it is necessary to surely access the start position of the data sector. As a method of determining the head position of the data sector, there is a method of recording specific information called an address mark on the disk 1 in advance and generating a read signal when the specific information is detected. However, this method has a drawback that the data recording area is reduced by the area because it is necessary to prepare an area for recording the address mark on the disk 1.

As another method, counting is started from the generation of the servo index pulse in the servo area, the position of the servo area is specified by the number of the count value (servo number), and the start position of the data sector is determined. There is a way to decide. However, with this method, accurate counting becomes impossible when the servo sector pulse does not occur continuously. Normally, if no servo sector pulse is continuously generated within a time interval 1.2 times the servo sector pulse generation interval, it is determined that there is a pulse generation omission for some reason.
For example, even if a servo sector pulse is generated after five consecutive skips, the position cannot be accurately specified. This is because there is an error in the normal generation interval. For example, when a pulse occurs immediately after the measurement of five consecutive omissions, the number of omissions due to the actual continuous measurement time is 5, whereas the actually generated pulse starts from the position where the omission starts. Since it is the sixth, an error may occur in a simple counting operation.

Further, when the head switching operation is executed, there is a possibility that the counting of the servo numbers may be erroneous due to the switching timing of the head selection. This is because the position where the servo data is recorded may not match between the front surface and the back surface of the disk 1. In particular,
As shown in FIG. 8, the front surface of the disk 1 is a data surface A and the back surface is a data surface B. In this case, for example, when the head A corresponding to the data surface A is switched to the head B corresponding to the data surface B, the count value “11” and the servo number “10” do not match.

The present invention has been made in consideration of the above circumstances, and an object thereof is to record servo code information for identifying a servo area at a predetermined position of each servo area recorded on a disk. , By identifying the servo area based on the servo code information, the identified servo area can be recorded even if the servo sector pulse does not occur continuously without providing a specific area for recording the address mark on the disk. To provide a data recording / reproducing apparatus and a servo processing method capable of accurately detecting the head position of a corresponding data sector and accurately performing the detection of the head position of the data sector even if the servo code information cannot be correctly extracted. It is in.

Another object of the present invention is to provide a data recording / reproducing apparatus and a servo processing method capable of reliably estimating accurate servo code information when the servo code information cannot be correctly extracted.

Still another object of the present invention is to suppress a series of processes for determining the start position of the data sector during a seek operation in which the determination of the start position of the data sector is unnecessary, thereby wasteful processing. It is an object of the present invention to provide a data recording / reproducing apparatus and a servo processing method that can reduce the load on the CPU by eliminating the occurrence of the above, and particularly when the series of processes is performed by the CPU. Still another object of the present invention is to provide a data recording / reproducing apparatus and a servo processing method capable of suppressing unstable servo code information estimation.

[0027]

According to the present invention, a head for recording / reproducing data is positionally controlled at a specified position on a disk based on servo data recorded in each servo area set on the disk. In the data recording / reproducing apparatus, servo code information for identifying the servo area is recorded at a predetermined position of each servo area, and the servo code information is extracted every time the servo code information is extracted from the servo area by the extracting means. Is detected correctly, and an erroneous extraction detecting means for detecting an erroneous extraction of the servo code information, and an erroneous extraction of the servo code information is detected by this erroneous extraction detecting means,
It was determined that the servo code information was correctly extracted by the estimation means for estimating the correct servo code information based on the preceding servo code information used to determine the head position of the previous data sector and the incorrect extraction detection means. in case of,
When erroneous extraction is determined based on the servo code information, one or more corresponding to the servo area identified by the servo code information based on the servo code information estimated by the estimating means. And a determining means for determining the leading position of the data sector.

According to the present invention, when the servo code information is correctly extracted by the extracting means, the servo code information is held, and when the erroneous extraction of the servo code information is detected by the erroneous extraction detecting means. The present invention is also characterized in that it further comprises holding means for holding the servo code information estimated by the estimating means, and can be used for estimation when the servo code information is not correctly extracted from the servo area next.

Further, according to the present invention, the number of times that erroneous extraction is not continuously detected by the erroneous extraction detecting means from the end of the seek operation is counted, and until the number of times reaches a predetermined value, the data sector by the deciding means is counted. It is also characterized in that it further comprises position determination inhibiting means for inhibiting the determination of the leading position of the.

The present invention is also characterized in that during the seek operation, the determination of the data sector head position by the determining means is suppressed by the position determination suppressing means. Further, the present invention further comprises an estimation deterring means for counting the number of times the servo code information is successively estimated by the estimating means, and suppressing the estimation by the estimating means when the number of times reaches a predetermined value. Also features.

[0031]

In the above structure, the extracting means extracts the servo code information (for example, the servo sector number assigned to each servo area) recorded at a predetermined position in each servo area of the disk. The erroneous extraction detection means detects erroneous extraction of the servo code information by determining whether or not the servo code information is correctly extracted each time the extraction means extracts the servo code information. The determination here is performed by, for example, checking whether or not the servo code information has been correctly decoded. In addition, even if the decoding is successful, the decoded servo code information is the servo code information extracted from the preceding servo area (that is,
It is performed by checking whether or not the preceding servo code information) is continuous.

In this way, when the erroneous extraction detecting means determines that the servo code information has been correctly extracted, the servo area identified by the servo code information is identified on the basis of the extracted servo code information. The deciding means performs the process of deciding the head positions of the corresponding one or more data sectors. To determine the start position of this data sector, for example, for each servo code information,
Format information of a data sector corresponding to the servo area identified by the servo code information (specifically, one or more data sectors set in a data area subsequent to the servo area next to the servo area) ( If the servo code information is correctly extracted by the extracting means, the corresponding format information (timing data) is stored from the storing means based on the servo code information. Just search. In addition, when the CDR system in which the disk is divided into a plurality of zones in the radial direction and each zone includes a plurality of tracks is applied, the servo for each servo code information is changed for each zone. When the format information of the data sector corresponding to the servo area identified by the code information is stored in the storage unit and the servo code information is correctly extracted, the zone (the zone number indicating the zone) to be accessed and the servo concerned. The corresponding format information may be retrieved from the storage means based on the code information.

On the other hand, when the wrong extraction of the servo code information is detected by the wrong extraction detecting means, the estimating means is activated. Then, the estimating means increments the servo code information (servo sector number) by 1 based on the preceding servo code information (servo sector number) obtained last time, and the correct servo code that should have been obtained this time should be obtained. Information (servo sector number) is estimated, and the estimated servo code information is used in place of the servo code information in which erroneous extraction is detected, for determining the start position of the data sector by the determining means.

As a result, even if the correct servo code information (servo sector number) cannot be extracted for some reason, the head position of the data sector corresponding to the servo area can be accurately detected, and the data recording / reproduction is correct. You can do it.

In the above arrangement, in order to enable the estimation of the servo code information by the estimation means, when the servo code information is correctly extracted, the servo code information is held as the preceding servo code information. . Further, even if the servo code information is not correctly extracted, the servo code information estimated by the estimating means is held as the preceding servo code information. Therefore, even if erroneous extraction of servo code information occurs continuously, correct servo code information can be obtained. However, since it is not a normal state that the erroneous extraction of the servo code information occurs continuously, the number of times of continuous estimation is limited. The estimation deterrent means realizes the limitation of the number of continuous estimations. The number of consecutive estimations is counted, and when the prescribed number of times is reached, the estimation by the estimation means is deterred and the system This prevents the determining unit from determining the data sector head position in an abnormal state.

Further, in the above configuration, even if the servo code information is correctly extracted until the error-free servo code information is continuously extracted a prescribed number of times with reference to the end of the seek operation. The determination of the data sector head position by the determination means is suppressed by the position determination suppression means. By such control, it is possible to stably determine the head position of the data sector, and the servo code information serving as a reference used by the estimating means becomes reliable, so that the correct estimation is guaranteed.

Further, in the above configuration, during the seek operation, the determination of the data sector head position is inhibited by the position determination inhibiting means. More specifically, the erroneous extraction detecting means checks whether or not the servo code information has been correctly extracted, and when the servo code information cannot be correctly extracted, the estimating means estimates the correct servo code information, and estimates the same. A series of processes for determining the start position of the data sector by the determining means based on the servo code information is suppressed. During this seek operation, it is not necessary to determine the data sector head position. Therefore, by suppressing the above series of processing during the seek operation, it is possible to eliminate the occurrence of useless processing. When the CPU is performed, the time required for the processing can be used for other processing, and the processing speed of the device can be improved.

[0038]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a hard disk drive (HD
2) is a conceptual diagram showing the format of the servo area according to the embodiment, FIG. 4 is a block diagram showing the configuration of the data sector pulse generation circuit, and FIG. 5 is data. Timing charts for explaining the operation of the sector pulse generating circuit, and FIGS. 6 and 7 are flow charts for explaining the operation of the embodiment.

The HDD is a disk rotating mechanism for rotationally driving a disk 1 as a recording medium, a servo mechanism for positioning the head 2 on a target cylinder on the disk 1, and a read / write for recording / reproducing data. It has a circuit system 3. The disk rotating mechanism is composed of a spindle motor 4, which drives the disk 1 to rotate, a motor driver 5, and a motor control circuit 6.

The servo mechanism includes a carriage mechanism 7 for holding the head 2, a voice coil motor (VCM) 8 for driving the carriage mechanism 7, a VCM driver 9, a VCM control circuit 10, and a servo processing circuit for driving the VCM 8. 11 and a data sector pulse generation circuit 17.

The VCM control circuit 10 is the servo processing circuit 1
The VCM driver 9 is controlled according to the control amount output from 1 to drive and control the VCM 8. Servo processing circuit 11
Extracts the cylinder address code, the burst data (position signal), and the servo sector number described later from the servo data reproduced by the read / write circuit system 3 and outputs them to the CPU 12. Also, the servo processing circuit 11
Converts the digital control amount from the CPU 12 into D / A and outputs the analog control amount to the VCM control circuit 10. The data sector pulse generation circuit 17 includes one or more data sectors corresponding to (servo sectors having) the servo area identified by the servo sector number extracted by the servo processing circuit 11, more specifically, the servo sector number. Servo area (servo sector) next to (servo sector having) that is identified by
A data sector pulse is generated at a timing corresponding to each head position of one or more data sectors set in the data area subsequent to. Data representing this timing is set by the CPU 12.

The read / write circuit system 3 roughly includes an encoder / decoder 3a for processing user data and a signal processing circuit 3b for processing servo data. The encoder / decoder 3a converts the NRZ code write data transferred from the HDC (hard disk controller) 13 into a write signal (write current),
Supply to the head 2. The head 2 generates a recording magnetic field corresponding to write data by the write current, and the disk 1
Record above. Further, the encoder / decoder 3 a converts the read signal read from the disk 1 by the head 2 into reproduced data of NRZ code and transfers it to the HDC 13.

The signal processing circuit 3 b processes the servo data including the cylinder address code and burst data of the servo area read by the head 2 and outputs it to the servo processing circuit 11. The signal processing circuit 3b pulsates the cylinder address code and outputs it to the servo processing circuit 11. The servo processing circuit 11 has a circuit for decoding a cylinder address code from the data pulse from the signal processing circuit 3b. Further, the signal processing circuit 3b samples and holds the peak of the burst data, and the servo processing circuit 1
Output to 1. The servo processing circuit 11 is a signal processing circuit 3b.
The burst data from A / D is converted and output to the CPU 12.

The CPU 12 uses the cylinder address code from the servo processing circuit 11 to execute the speed control of the head 2 based on the program stored in the ROM 14. Further, the CPU 12 uses the burst data from the servo processing circuit 11 to execute the position control of the head 2.

The HDC 13 constitutes an interface between the host system (computer) 15 and the HDD and controls the transfer of read / write data. HDC13
Buffer RAM 1 for read / write data in sector units
The read data (reproduced data) is transferred to the host system 15, and the write data is transferred to the read / write circuit system 3.

In the HDD having such a configuration, in this embodiment, a servo code area (servo address code area) 20 is provided at a predetermined position of each servo area (SA) on the disk 1 as shown in FIG. Has been. As a specific example, as shown in FIGS. 3A and 3B, an area adjacent to the cylinder code area 13e is set as the servo code area 20.

In the servo code area 20, servo code information for identifying the area 20 (servo sector having a head position thereof), for example, a servo sector number (servo address code) is recorded.

In the present embodiment, as shown in FIG. 13, a servo index pulse is generated in each servo area (having servo sectors) set at predetermined intervals in the circumferential direction of the disk 1 (sector). /index·
The servo area (having the pattern area 13d) (servo sector having) is assigned "0" as the servo sector number, and hereinafter, each subsequent servo area (serving servo sector) has "1" as the servo sector number.
“2” ... Is assigned in order.

Next, the structure of the data sector pulse generation circuit 17 will be described. Data sector pulse generation circuit 1
7 is a first and second register group 4 as shown in FIG.
It has 0, 41, a selector 42, a control circuit 44, and a timer circuit 46.

The first and second register groups 40 and 41 respectively include initial value registers 40a and 41a and reload (relo).
ad) Registers 40b and 41b and reload count registers 40c and 41c.

The initial value registers 40a and 41a are used to hold the parameter value (initial value) TS set in the timer circuit 46 at the initial stage. This value TS is the generation timing (servo sector pulse) of the first data sector pulse DSP (according to the head position of the data sector) in the servo sector next to the servo sector identified by the servo sector number extracted by the servo processing circuit 11. SS
First data sector pulse DS based on the position of P
It is time information (timer information) that gives the start position of P).

After the initial operation of the timer circuit 46 is completed, the reload registers 40b and 41b are provided with the timer circuit 46 again.
It is used to hold the parameter value TP set to. This value TP is time information (timer information) that gives the repetition cycle of the data sector pulse.

The reload count registers 40c and 41c are
A parameter value (the number of data sectors in the servo sector) dn indicating the number of repetitions when the contents of the reload registers 40b and 41b are set and the operation of the timer circuit 46 is repeated.
Used to hold the.

Next, the operation of the embodiment will be described. In this embodiment, a CDR type HDD is assumed. In the CDR system, as shown in FIG. 13, the disk 1 is radially divided into a plurality of zones, and each zone includes several tens to several hundreds of cylinders.

The servo area SA is radially recorded on the disk 1 over each zone. Therefore, the servo area SA is not necessarily located at the head of each sector. As a specific example, as shown in FIG.
In a certain servo sector based on the servo area SA,
It is assumed that the format includes the second half of the data sector A, a plurality of data sectors B, C, and D that are continuous with the latter half, and the first half of the data sector E.

Here, in the configuration of FIG. 1, when a read access request is issued from the host system 15, for example, C
The PU 12 executes a process of controlling the positioning of the head 2 on the target cylinder to be accessed. At this time, the physical address including the zone number, cylinder address, head number, and sector number on the disk 1 to be accessed is
It is obtained by converting the logical address from the host system 15 by the HDC 13.

The servo processing circuit 11 outputs the cylinder address code and burst data (position signal) read from the cylinder code area 13e and burst pattern area 13g of the servo area SA by the head 2 to the CPU 12
Output to. The CPU 12 executes speed control for moving the head to the target cylinder based on the cylinder address. Further, the position control for positioning the head at the center of the target cylinder is executed based on the burst data.

Further, the servo processing circuit 11 is arranged so that the sector / index pattern area 13d of the servo area SA is
Based on the read signal from the servo sector pulse SS
P or servo index pulse SIP is generated.
Based on the servo sector pulse SSP, the CPU 12 detects that the servo area SA has been read by the head 2. Further, the reference point of the cylinder is detected by the servo index pulse SIP.

When the head 2 is positioned in the target cylinder, it reads the user data from the data sector in the target cylinder and outputs it to the read / write circuit system 3. The encoder / decoder 3a of the read / write circuit system 3 is
The read signal read by the head 2 is converted into an NRZ code and output to the HDC 13. The HDC 13 temporarily stores this in the buffer RAM 16 and transfers the read data in sector units to the host system 15.

Here, when a write access request is issued from the host system 15, the encoder / decoder 3a of the read / write circuit system 3, conversely to the above, writes the write data of the NRZ code transferred from the HDC 13 to the write signal ( Write current) and output to the head 2. The head 2 records the write data in the data sector of the target cylinder.

In such a read / write access operation, in order to access the designated data sector for which an access request has been made, the ID information of the ID area is first referenced, and the sector to be accessed is based on this ID information. You need to be aware of that. In order to surely access the ID area at the head position of the data sector, in this embodiment, the CPU 12 activates the data sector pulse generation circuit 17 in response to the servo sector number extraction by the servo processing circuit 11, and the position of the ID area. Data sector pulse DSP is generated.

The operation from the extraction of the servo sector number to the generation of the data sector pulse DSP will be described with reference to FIGS. 4 to 7. Now, the servo processing circuit 11 extracts the servo sector number (servo code information) recorded in the servo code area 20 of the servo area SA by the decoder circuit having the same configuration as the decoder circuit for decoding (reproducing) the cylinder address code. It is assumed to be decrypted. Then, the servo processing circuit 11 interrupts the CPU 12.

In the CPU 12, the servo sector number is decoded by the servo processing circuit 11 and the servo processing circuit 11 concerned.
Each time an interrupt is input from, each data sector corresponding to the servo sector specified by the decoded servo sector number (specifically, each data sector starting from the ID area in the servo sector next to the servo sector indicated by the decoded servo sector number) ) Start position (position of ID area)
In order to generate the data sector pulse DSP at the timing according to, the process according to the flowcharts of FIGS. 6 and 7 is started.

First, the CPU 12 checks whether or not the seek operation is in progress (step S1). If the seek operation is in progress, the CPU 12 determines that the generation of the data sector pulse is unnecessary, and sets a prescribed value n3 to an error counter EC (Error Counter) as a software counter (variable) (step S2). , No processing is performed on the generation of the data sector pulse (step S3). This reduces the load on the CPU 12. The specified value applied in this embodiment is the above n.
In addition to 3, there are n1 and n2, and the magnitude relationship between them is n1 <
n2 ≦ n3.

On the other hand, if the seek operation is not in progress, the CPU 1
In No. 2, it is necessary to generate the data sector pulse, and the processing for that is performed as follows. First, the CPU 12
Is a variable CSN (Current Sector Num) that indicates the current servo sector number by fetching the servo code number decoded by the servo processing circuit 11 from the servo processing circuit 11.
ber) (step S4).

Next, the CPU 12 checks whether or not the value of the error counter EC is larger than the specified value n1 (step S
5). If the seek operation has just been completed, the error counter EC is set to the specified value n3 (by step S2).
Since (n3> n1) is set, the CPU 12 determines that the value of the error counter EC is larger than the specified value n1.

In this case, the CPU 12 is the servo processing circuit 1
It is checked whether or not there is a decoding error in the servo sector number decoded by 1 (step S6). Normally, the servo processing circuit 11 is adapted to decode the servo code recorded in the servo code area 20 by two methods to obtain two servo sector numbers. For this reason,
If the two obtained servo sector numbers do not match, it is determined that a servo sector number decoding error has occurred. Various decoding methods have been known in the past, and since they are not directly related to the present invention, description thereof will be omitted.

If there is a decoding error, the CPU 12 sets the specified value n3 in the error counter EC as in the seek operation (step S2) so as not to perform any processing regarding the generation of the data sector pulse. Yes (step S3).

On the other hand, if there is no decoding error, CP
U12 decrements the content of the error counter EC by -1, and also indicates a variable PSN (Previous S
The current servo sector number indicated by the variable CSN is set in (ector Number) (steps S7 and S8), and no processing relating to the generation of the data sector pulse is performed (step S3).

If the above steps S1 and S4 to S8 are repeated (n3-n1) times in succession, that is, (n3-n1) times in succession after the seek operation is completed, the correct servo sector number is obtained. If is decoded, the value of the error counter EC becomes n3- (n3-n1) = n1. Therefore, when the servo sector number is decoded next, the determination result of step S5 is No (EC ≦ n1). In this case, the CPU 12 proceeds to processing for generating a data sector pulse, as will be described later.

On the other hand, after the seek operation is completed,
The processing of steps S1 and S4 to S8 continues (n3-n
If a decoding error of the servo sector number is detected in step S6 before 1) times are repeated, the error counter EC is set to n3 again (step S6).
2) From then on, until the servo sector number is correctly decoded (n3-n1) times, the process proceeds from step S5 to step S6.

After the seek operation is completed, (n3-
The servo sector number is correctly decoded n1 times consecutively, and the CPU 12 returns No (EC ≦ n in step S5).
1) is determined, and the process proceeds to step S9. This step S9
Then, it is checked whether or not there is a decoding error in the decoded servo sector number.

If there is no decoding error, the CPU 1
2 is the servo sector number PSN and C immediately before the PSN.
It is checked whether or not the current servo sector number indicated by SN is continuous, that is, whether or not the current servo sector number is next to the immediately preceding servo sector number (step S1).
0).

When the current servo sector number is "0" indicating the first servo sector, the immediately preceding servo sector number has a predetermined maximum value indicating the last servo sector, and in this case also, the servo sector numbers are considered to be continuous. .

If the immediately preceding servo sector number and the current servo sector number are not consecutive, CPU 1
In No. 2, it is determined that the servo sector number decoded this time (current servo sector number) is incorrect although there was no decoding error. The operation when an error in the current servo sector number is detected in step S10 or step S9 will be described later.

On the other hand, if the immediately preceding servo sector number and the current servo sector number are consecutive, the CPU 12
Determines that there is no error in the servo sector number (current servo sector number) decoded this time, clears the error counter EC to "0" (step S11), and then (CS
The current servo sector number (indicated by N) is set in the variable PSN as the immediately preceding servo sector number (step S12).
The CPU 12 then uses the data sector pulse generation circuit 17
The process for setting up (1) and generating the data sector pulse DSP (step S13) is executed according to the flowchart of FIG.

Before describing the detailed operation of step S13, three types of parameters (TS, TP, dn) which are timing information set in the data sector pulse generation circuit 17 (register group 40 or 41 in the data sector pulse generation circuit 17). A table in which is stored for each servo sector number (not shown)
Will be described.

First, this table is set for each zone in a RAM (not shown) accessible from the CPU 12. Therefore, the table in which the necessary parameters are stored is designated by the zone number indicating the zone to be accessed (here, the base address determined by the zone number). Further, the storage position of the target parameter in the table is designated by the servo sector number (here, the data length of the servo sector number × 3 types of parameters).

In this embodiment, the parameter (timing information) stored in the storage position in the table designated by the servo sector number is the parameter for generating the data sector pulse in the servo sector indicated by the servo sector number next to the servo sector number. TS, TP, d
n.

When the zone number of the access target has been changed since the previous access, the CPU 12 changes the base address and changes the table to be referred to (steps S21 and S22).

Then, the CPU 12 uses the base address after the change (when the access target zone is changed) or the same base address as the previous time (when the access target zone is not changed) to correspond to the access target zone. A desired table is selected, and the three target parameters TS, TP, dn are acquired from the reference position in the table determined by the current servo sector number (step S23). Specifically, the reference position in the table corresponding to the zone to be accessed and the current servo sector number is referred to by “servo sector number × data length + base address”.

In the present embodiment, the timer circuit 46 in the data sector pulse generation circuit 17 operates in accordance with the parameters set in the first register group 40 in mode A and in the second register group 41. Two kinds of modes, that is, a mode B that operates according to the parameters are prepared, and apparently two timers are operated. Therefore, for convenience, the system of the first register group 40 and the timer circuit 46 is called a timer system A, and the system of the second register group 41 and the timer circuit 46 is called a timer system B.
The timer system A and the timer system B do not operate at the same time, and when one is operating, the other prepares to generate the next data sector pulse.

Assuming that the timer system A is the servo sector number sn
When the operation is in accordance with the data sector pulse generation parameters TS, TP, dn of -1 (in the servo sector), the CPU 12 generates the data sector pulse of the next servo sector number sn acquired from the table in step S23. The parameters TS, TP and dn are set to the registers 41a and 41 which form the register group 41 of the timer system B
b and 41c (steps S24 and S25).

Thereafter, the operation of the timer system A ends, and the servo processing circuit 11 is operated based on the read signal from the sector / index pattern area 13d recorded in the servo area SA of the servo sector of the servo sector number sn.
When the servo sector pulse SSP (or servo index pulse SIP) is generated by the timer system B, the timer system B sets the parameters TS, TP, d set in the register group 41.
The operation is started according to n, and the data sector pulse DSP is generated. During this period, the CPU 12 sets parameters TS, TP, dn for generating the data sector pulse of the next servo sector number sn + 1 in the register group 40 of the timer system A.

On the contrary, the timer system B determines the servo sector number sn.
-1 (in the servo sector) when operating according to the parameters TS, TP, dn for generating data sector pulses (that is, when the timer system A is not operating), the CPU 12
Sets the parameters TS, TP, dn for generating the data sector pulse of the next servo sector number sn acquired from the table in step S23 to the register group 4 of the timer system A.
It is set in the registers 40a, 40b and 40c which configure 0 (steps S24 and S26).

Thereafter, the operation of the timer system B is completed, and the servo processing circuit 11 is operated based on the read signal from the sector / index pattern area 13d recorded in the servo area SA of the servo sector of the servo sector number sn.
When the servo sector pulse SSP (or the servo index pulse SIP) is generated by the timer system A, the timer system A sets the parameters TS, TP, d set in the register group 40.
The operation is started according to n, and the data sector pulse DSP is generated. During this period, the CPU 12 sets parameters TS, TP, dn for generating the data sector pulse of the next servo sector number sn + 1 in the register group 41 of the timer system B.

Next, the detailed operation of the data sector pulse circuit 17 is obtained from the table based on the servo sector number sn-1 during the generation operation of the data sector pulse DSP (in the servo sector) of the servo sector number sn-1. Parameter T for generating the data sector pulse (in the servo sector) of the next servo sector number sn
As an example, S, TP, dn are set in the register group 40 of the timer system A, and then the servo processing circuit 11 generates the servo sector pulse SSP (or the servo index pulse SIP) of the servo sector number sn.
This will be described with reference to FIGS. 4 and 5.

First, the control circuit 44 uses the servo processing circuit 11
When the servo sector pulse SSP (or the servo index pulse SIP) is generated by the above, the timer system B, which has been operating until then, is switched to the timer system A as follows. That is, the control circuit 44 uses the first register group 4
Selection signal S for selecting the initial value register 40 in 0
By outputting EL, the selector 42 selects the parameter TS set in the initial value register 40,
The timer circuit 46 is loaded by the load signal LD.

The control circuit 44 controls the servo sector pulse SS
In synchronization with P, the timer circuit 46 count enable C
E is output and the timer circuit 46 is started. As a result, the timer circuit 46 performs the servo sector pulse SSP as shown in FIG. 5 by the timer operation (count operation) based on the parameter TS loaded from the initial value register 40a (via the selector 42) into the timer circuit 46. The data sector pulse DSP is generated at a timing after the lapse of TS from the time of occurrence of (TS is counted). This timing is I of the head data sector B in the servo sector of the next servo sector number sn according to the value of TS acquired according to the servo sector number sn-1.
It corresponds to the position of the D area.

The control circuit 44, when the first data sector pulse DSP is generated from the timer circuit 46, causes the above T
As in the case of loading S, the parameter TP set in the reload register 40b is loaded into the timer circuit 46 and the timer circuit 46 is restarted. As a result, the timer circuit 46 performs the timer operation (count operation) based on the parameter TP as shown in FIG.
The second data sector pulse DSP is generated at the timing after the TP has elapsed since the first data sector pulse DSP was generated (the timing at which the counting of TP was completed). This timing is determined by the value of TP acquired according to the servo sector number sn-1 and the next servo sector number s.
It corresponds to the position of the ID area of the data sector C in the n servo sectors.

Similarly, the timer circuit 46 repeats the timer operation (count operation) based on the parameter TP stored in the reload register 40b to generate the third and fourth data sector pulses DSP in the cycle TP. . The timings of the third and fourth data sector pulses DSP correspond to the positions of the ID areas of the data sectors D and E in the servo sector of the servo sector number sn. Here, the number of times the timer operation is repeated based on the parameter TP is determined by the parameter dn set in the reload number register 40c.

During the operation of the timer system A, as shown in FIG.
As shown in step S25 of step S25, the setup process for the timer system B (parameters TS, TP, dn for generating the data sector pulse of the next servo sector number sn + 1) is performed.
To the registers 41a, 41b in the second register group 41,
The processing of setting 41c) is executed by the CPU 12.

As described above, the data sector pulse generation circuit 17 indicates the parameters TS, TP, dn set by the setup process of the CPU 12, that is, the zone to be accessed and the extracted servo sector number (next servo sector). The data sector pulse DSP is generated at the timing corresponding to the position of the ID area of the data sector based on the timing data regarding the format of each data sector included in the (numbered) servo sector. With this data sector pulse DSP, the CPU 12
Reads the ID information from the ID area of each data sector and determines whether or not the data sector is an access target.

By the method of calculating the position of the ID area of each data sector from the position of the physical servo area on the disk 1 as described above, even if the servo sector pulse is not continuously generated, The position of the ID area of each data sector can be reliably detected. Although an area (servo code area 20) for recording the servo sector number is required, it is not as large as the area for recording the conventional address mark, and therefore the data recording area is not reduced. Absent.
Furthermore, the position where the servo data is recorded is the disk 1
Even if the head switching operation is executed when the front surface and the back surface of the disk do not match, the ID of each data sector
The position of the area can be reliably detected.

Next, the operation when the error in the current servo sector number is detected in step S9 or S10 will be described. In this case, the CPU 12 causes the error counter E
It is checked whether the value of C is larger than the specified value n1 (step S14). If the immediately preceding servo sector number indicated by PSN at that time (that is, the preceding servo sector number obtained last time) is correctly decoded, the error counter EC is cleared to "0" in the processing of step S11. Therefore, the determination in step S14 is No.
(EC <n1).

The CPU 12 makes a negative determination in step S14.
If o (that is, if the value of the error counter EC is less than or equal to the specified value n1), the servo sector number obtained last time, that is, PS
Based on the immediately preceding servo sector number indicated by N, the correct servo sector number to be obtained this time is estimated and set in the variable CSN (step S15). Specifically, the correct servo sector number is estimated by incrementing the immediately preceding servo sector number indicated by PSN. However, when the immediately preceding servo sector number has a predetermined maximum value, that is, when the servo sector indicated by the immediately preceding servo sector number is the final servo sector, "0" indicating the first servo sector is given as the correct servo sector number.

After executing step S15, the CPU 12 increments the content of the error counter EC by 1 (step S
16). The value of the error counter EC at this time indicates the number of times the servo sector number is continuously estimated after being cleared to "0" in the process of step S11.

After executing step S16, the CPU 12 sets the current servo sector number (indicated by CSN), that is, the servo sector number estimated in step S15, to the variable PSN as the immediately preceding servo sector number (step S1).
2). Then, the CPU 12 determines the data sector pulse generation circuit 1 based on the current servo sector number (indicated by CSN).
7 is set up and a process for generating the data sector pulse DSP (step S13) is performed.

As described above, when there is a decoding error in the servo sector number extracted by the servo processing circuit 11,
Alternatively, even if the correct servo sector number cannot be obtained, it is held as the immediately preceding servo sector number PSN,
The correct servo sector number to be obtained this time can be estimated based on the correct servo sector number obtained last time. Therefore, based on this estimated servo sector number, the data sector pulse generation circuit 17 can be set up correctly as in the case where there is no error in the extracted servo sector number, and the next servo sector pulse S
Data recording and reproduction of data can be correctly executed by generating an error-free data sector pulse DSP based on the timing of SP.

However, the estimation process of step S15, that is, the continuous estimation of the servo sector number is not a normal state, and the repetition of the estimation may cause the true number and the estimation result to not match. . Therefore, in this embodiment, when an error in the servo sector number is detected in step S9 or S10, it is checked whether the value of the error counter EC is n1 or more as described above (step S14), and n1 is reached. If the servo sector number is estimated successively n1 times, the servo sector number is not estimated any more and the data sector pulse generation circuit 17 stops generating the data sector pulse. . As a result, the true number does not match with the estimation result due to continuous estimation of the servo sector number,
It is possible to prevent the data sector pulse DSP from being generated at an incorrect timing.

When the CPU 12 determines in step S14 that the value of the error counter EC is n1 or more,
The specified value n2 (n1 <n2 ≦ n3) in the error counter EC
Is set (step S17), and no processing regarding the generation of the data sector pulse is performed (step S3).

When the error counter EC is set to n2, EC> n1. Therefore, when the servo processing circuit 11 extracts the next servo sector number, the determination in step S5 becomes Yes, and the process proceeds to step S6. If there is no servo sector number decoding error, the content of the error counter EC is decremented by 1 (step S7). Then, the current correct servo sector number indicated by CSN is set in PSN (step S8), and no processing relating to the generation of the data sector pulse is performed (step S8).
3).

From the above, after it was detected in step S14 that the servo sector number was estimated n1 times in succession, no decoding error of the servo sector number occurred (n2-n1) times in succession. Then, the value of the error counter EC is n2- (n2-n1) = n1. As a result, when the servo sector number is decoded next, the determination result of step S5 becomes No (EC ≦ n1), the process proceeds to step S9, and the process necessary for generating the data sector pulse is performed.

In other words, after the estimation of the servo sector number is performed n1 times in succession, until the correct servo sector number is decoded from there (n2-n1) times in succession.
The process does not proceed from step S5 to step S9, and no processing regarding the generation of the data sector pulse is performed.

When a servo sector number decoding error occurs in the middle, the error counter EC is set to the specified value n.
Since 3 is set (step S2), as with the end of the seek operation, until the correct servo sector number is continuously decoded (n3-n1) times thereafter, no processing regarding the generation of the data sector pulse is performed. Not done Due to the above restrictions, the immediately preceding servo sector number indicated by PSN when the process related to the generation of the data sector pulse is guaranteed.

[0106]

As described in detail above, according to the present invention, servo code information for identifying the servo area is recorded at a predetermined position of each servo area recorded on the disk, By identifying the servo area based on the code information, the data corresponding to the identified servo area can be created without providing a specific area for recording the address mark on the disk and even if the servo sector pulse does not occur continuously. The head position of the sector can be detected accurately, and the data sector head position can be detected accurately even if the servo code information cannot be extracted correctly.

Further, according to the present invention, the determination of the data sector head position is suppressed until the error-free servo code information is continuously extracted a prescribed number of times, based on the end of the seek operation. Therefore, the head position of the data sector can be stably determined, and the servo code information serving as a reference for the estimation becomes reliable, so that the correct estimation is guaranteed.

Further, according to the present invention, a series of processes for determining the start position of the data sector (that is, whether or not the servo code information has been correctly extracted is checked, and when the servo code information has not been correctly extracted, the correct servo is obtained. A series of processes for estimating the code information and determining the head position of the data sector based on the estimated or correctly extracted servo code information)
Is configured to be suppressed during the seek operation in which the determination of the data sector head position is unnecessary, so that unnecessary processing is eliminated, and particularly when the above series of processing is performed by the CPU, the CPU load is reduced. Can be reduced.

Further, according to the present invention, by setting an upper limit on the number of times the servo code information is continuously estimated,
It is possible to prevent unstable servo code information estimation from being performed in an abnormal state of the system.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a hard disk device (HDD) according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a format of a servo area according to the embodiment.

FIG. 3 is a conceptual diagram showing a format of a servo area according to the embodiment.

FIG. 4 is a block diagram showing a configuration of a data sector pulse generation circuit according to the embodiment.

FIG. 5 is a timing chart for explaining the operation of the data sector pulse generation circuit according to the embodiment.

FIG. 6 is a flowchart for explaining the operation of the embodiment.

7 is a flowchart for explaining a data sector pulse generation circuit setup process in FIG.

FIG. 8 is a conceptual diagram for explaining a conventional head switching operation.

FIG. 9 is a conceptual diagram for explaining the configuration of a conventional servo area.

FIG. 10 is a conceptual diagram for explaining a conventional CDR disc format.

FIG. 11 is a conceptual diagram for explaining the configuration of a conventional servo area.

FIG. 12 is a signal waveform diagram for explaining a conventional data reproducing operation.

FIG. 13 is a conceptual diagram for explaining a conventional CDR disc format.

FIG. 14 is a conceptual diagram for explaining the configuration of a conventional servo area.

FIG. 15 is a conceptual diagram for explaining the configuration of a conventional ID area.

FIG. 16 is a conceptual diagram for explaining a conventional disc format.

[Explanation of symbols]

1 ... Disk, 2 ... Head, 3 ... Read / write circuit system, 11 ... Servo processing circuit, 12 ... CPU, 13 ... HD
C, 15 ... Host system, 17 ... Data sector pulse generation circuit, 40, 41 ... Register group, 40a, 41a ...
Initial value register, 40b, 41b ... Reload register,
40c, 41c ... Reload count register, 44 ... Control circuit, 46 ... Timer circuit.

Claims (11)

[Claims] 1. A data recording / reproducing apparatus for positioning and controlling a head for recording / reproducing data at a designated position on the disk based on servo data recorded in each servo area set on the disk, Based on the servo code information extracted by this extracting means, which is specific information recorded at a predetermined position in each servo area, and which extracts servo code information for identifying each servo area, Determining means for determining a head position of one or more data sectors corresponding to the servo area identified by the servo code information, and the servo code information is stored every time the servo code information is extracted by the extracting means. An erroneous extraction detecting means for determining whether the servo code information is correctly extracted, When the erroneous extraction of the servo code information is detected by the erroneous extraction detecting means, the correct servo code information is estimated based on the preceding servo code information obtained last time, and the estimated servo code information is used as the erroneous value. A data recording / reproducing apparatus, characterized in that, in place of the detected servo code information, there is provided an estimating means used by the determining means for determining the start position of the data sector. 2. A data recording / reproducing apparatus for controlling the positioning of a head for recording / reproducing data at a designated position on the disk, based on servo data recorded in each servo area set on the disk, Storage means for storing format information relating to positions of one or more data sectors respectively corresponding to each servo area, and specific information recorded at a predetermined position of each servo area for identifying each servo area Corresponding to the servo area based on the format information in the storage means corresponding to the servo area identified by the servo code information extracted by the extracting means, Determining means for determining the start position of each of the data sectors, and Each time the servo code information is extracted, it is determined whether or not the servo code information is correctly extracted, and an erroneous extraction detecting means for detecting erroneous extraction of the servo code information; When erroneous extraction of code information is detected, the correct servo code information is estimated based on the preceding servo code information obtained last time, and the estimated servo code information is used as the servo code information in which the erroneous extraction is detected. In place of the above, the data recording / reproducing apparatus is provided with an estimating means used for determining the start position of the data sector by the determining means. 3. When the erroneous extraction means determines that the servo code information has been correctly extracted, the servo code information correctly extracted by the extraction means is held and the erroneous extraction detection means holds the servo code information. When erroneous extraction of information is detected, it further comprises a holding means for holding the servo code information estimated by the estimating means, wherein the estimating means calculates the servo code information held in the holding means. 3. The data recording / reproducing apparatus according to claim 1, wherein correct servo code information is estimated based on the original. 4. The number of times that the erroneous extraction is not continuously detected by the erroneous extraction detecting means from the end of the seek operation is counted, and until the number of times reaches a predetermined value, the deciding means stores the data sector 4. The data recording / reproducing apparatus according to claim 3, further comprising position determination inhibiting means for inhibiting the determination of the head position. 5. The data recording / reproducing apparatus according to claim 4, wherein the position determination inhibiting means inhibits the determination of the head position of the data sector by the determining means during a seek operation. 6. The method further comprises an estimation deterring means for counting the number of times the servo code information is successively estimated by the estimating means, and suppressing the estimation by the estimating means when the number of times reaches a predetermined value. Claim 1 characterized by the above.
Alternatively, the data recording / reproducing apparatus according to claim 2. 7. The servo code information for identifying the servo area, which is recorded at a predetermined position of each servo area set on the disk, is extracted, and the servo code information is extracted based on the extracted servo code information. Servo applied to a data recording / reproducing apparatus for determining the start position of one or more data sectors corresponding to the servo area identified by the code information and recording / reproducing data for the designated data sector. A processing method, wherein each time the servo code information is extracted from the servo area, a first step of determining whether or not the servo code information is correctly extracted, and the servo code in the first step A second step of estimating the correct servo code information based on the preceding servo code information obtained last time when erroneous extraction of information is determined. If it is determined that the servo code information is correctly extracted in the first step, it is determined that the servo code information is erroneously extracted in the first step based on the correctly extracted servo code information. If so, the third step of determining the head position of the data sector corresponding to the servo area identified by the servo code information based on the servo code information estimated in the second step. And a servo processing method. 8. If it is determined in the first step that the servo code information is correctly extracted, the correctly extracted servo code information is held as the preceding servo code information, and the second servo code information is stored. When the estimation is performed in stages, the estimated servo code information is retained as the preceding servo code information, so that the estimation is performed when the servo code information is not correctly extracted from the servo area next time. 8. The servo processing method according to claim 7, wherein the servo processing method is applicable to the above. 9. From the end of the seek operation, the number of times that erroneous extraction is not detected in the first step is counted continuously, and the third step is suppressed until the number reaches a predetermined value. 9. The servo processing method according to claim 8, wherein: 10. The servo processing method according to claim 9, wherein the third step is suppressed during a seek operation. 11. The number of times the servo code information is estimated in succession in the second step is counted, and if the number of times reaches a predetermined value, the second step is suppressed. The servo processing method according to claim 7.