JP4145474B2 - Magnetic disk drive and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, when a servo data reading error in a magnetic disk device may cause a malfunction in timing generation for detecting the next servo data, specifically, when a head is switched or start bit detection times out. And a timing generation method for reading servo information of the same.
[0002]
[Prior art]
Conventionally, in a hard disk drive (HDD), a read head that reads servo information recorded on a media surface is driven by a rotary actuator. Therefore, when the read head seeks on the media surface, the head draws an arc orbit. Moving.
[0003]
When the read head is positioned with respect to the target track, the timing at which the read signal is generated to read the servo information is slightly shifted by the rotational fluctuation of the spindle motor. Depending on the seek direction, the time until the servo data area including the servo information reaches the read head differs. For this reason, it is known to adjust the timing generation of the read signal in accordance with the time until the servo data area reaches the read head during seek (for example, Japanese Patent Application No. 11-22371). .
[0004]
Generation of various timings for acquiring servo information is performed based on the time from detection of the start bit. The start bit is predetermined information existing in the servo data area, and is arranged near the head of each servo sector. The start bit is detected by the start bit detector, but this timing generation is performed in the time from the start bit detection one sample before. For this reason, when an unexpected timing occurs, such as when the start bit is not found, when the start bit is detected in the wrong place, or when the head is shifted when the head is displaced, There was a problem that the generation timing in the next sector was shifted.
[0005]
In the prior art, the interval of the previous servo data is measured according to the time fluctuation during the seek with reference to the start bit, and the time is dynamically set based on the measured interval. However, in such a system, the servo data interval (generation timing) used for the next sector when the reference star and bit are erroneously detected or lost, or when the head is switched, etc. There is a problem that once the timing is deviated, the start bit is repeatedly omitted, and the seek time of the entire magnetic disk device is extended.
[0006]
In other words, in the prior art, various timings for acquiring servo information are generated based on the previous servo data at the seek time, and the start bit is shifted due to erroneous start bit detection or head switching. If this happens, reading will start sooner than the servo data that should be read, or the servo data has arrived, but the time has not been reached, so the reading will be performed quickly. The problem that it does not occur. At this time, as in the prior art, even if the timing for servo data reading is dynamically set according to the time fluctuation during seeking, unexpected phenomena such as missing start bits and head switching as described above may occur. I couldn't respond to what happened.
[0007]
To explain with a specific example, the AGC gain is adjusted by the AGC area at the head of the servo data, and the AGC control signal is controlled by time so that the AGC gain is fixed in the subsequent erase area. These timings are generated based on the start bit detected in the servo area one sample before.
[0008]
In this way, even if the AGC control signal is controlled at a predetermined time in consideration of fluctuation due to seek, if the start bit is delayed and the arrival of servo data is early, the AGC area can be moved from the erase area to the AGC area. Gain adjustment starts.
[0009]
Conversely, if the start bit is advanced and the arrival of servo data is late, AGC gain adjustment is started from the user data area before the servo data.
[0010]
In either case, since the AGC gain adjustment is performed in a portion other than the AGC area, the gain is not adjusted correctly. As a result, in some cases, the servo data following the AGC area cannot be read correctly, and there is a possibility that a problem may occur in seek control.
[0011]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to detect the previous servo data when there is a possibility of erroneous detection of the servo data, such as when a start bit is erroneously detected, the start bit is missing, or the head is switched. By clearing the timing and stopping the timing generation by the interval until the next servo data interval is correctly obtained, it is possible to prevent the control from being lost due to the start bit missing state continuing.
[0012]
[Means for Solving the Problems]
In the present invention, when there is a possibility that the servo data reading timing may be incorrect, the servo data interval measured before that is not used so that the next servo data is not affected. The present invention relates to a magnetic disk device having a function of initializing a timer for newly measuring a servo data interval so as to stop timing generation.
[0013]
The magnetic disk apparatus of the present invention includes a timer, a count value holding means for holding a count value generated by the timer, and a servo information reading timing signal based on the time count value from the previous sector counted by the timer. In a sector servo type magnetic disk apparatus equipped with a timing generation means for generating, detection means for detecting the presence or absence of head switching, or the presence or absence of a start bit indicating the start position of a servo sector, and the detection means has switching of the head, Alternatively, when it is detected that the start bit detection exceeds a predetermined time, timing generation stop means for stopping generation of the next servo information reading timing signal based on the servo information reading timing one sample before; It is characterized by having .
[0014]
With such a configuration, when the start bit cannot be detected due to missing start bit or timing shift due to head switching, the servo gate is reset and the AGC is held so that the start bit can always be detected. Further, by setting a timer, the count of detection timing occurrence in the next sector is not affected by the previous timing value. As a result, it is possible to prevent the servo data from being taken in for an unexpected cause.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments in which the present invention is applied to a magnetic disk device will be described with reference to the drawings.
[0016]
FIG. 1 is a block diagram showing a configuration of a magnetic disk apparatus according to an embodiment of the present invention.
[0017]
In FIG. 1, 11 is a disk medium (magnetic disk) on which data is recorded, and 12 is a head (magnetic head) used for head writing to the disk medium 11 and data reading from the disk medium 11. The head 12 is provided corresponding to each surface (recording surface) of the disk medium 11. 1 assumes a magnetic disk device in which two disk media 11 are stacked.
[0018]
A number of concentric tracks are formed on both recording surfaces of the disk medium 11 as shown in FIG. A so-called sector servo system (embedded servo system) format is applied to the format of the disk medium 11, and each track is equally divided into a plurality of sectors (servo sectors) 100. Each servo sector 100 includes a servo area 110 in which servo data is recorded, and a user data area 120 in which data (user data) is recorded (constituting a plurality of data sectors). The servo areas 110 are arranged radially at equal intervals across the tracks from the center on the disk medium 11.
[0019]
As shown in FIG. 3, the servo area 110 is used to identify and determine the reference position of the AGC area 111, the erase area 112, and the servo area 110 in which data of a certain frequency is recorded in order to stabilize the amplitude of the signal. A reference signal area 113 in which a reference signal to be used is recorded, a cylinder address (cylinder code) indicating a cylinder number, and burst data for detecting a head position (position error) in the cylinder indicated by the cylinder address are recorded. Address / burst area 114.
[0020]
The head 12 is attached to a rotary head actuator 13 as a head moving mechanism, and an arc 200 is drawn in the radial direction of the disk medium 11 as shown in FIG. 2 according to the rotation (angular rotation) of the head actuator 13. Moving. As a result, the head 12 is seeked and positioned on the target track.
[0021]
The disk medium 11 is rotated at high speed by a spindle motor (hereinafter referred to as SPM) 14. The head actuator 13 has a voice coil motor (hereinafter referred to as VCM) 15 that is a drive source of the head actuator 13, and is driven by the VCM 15.
[0022]
The SPM 14 is driven by a control current (SPM current) supplied from the SPM driver 16. The VCM 15 (having the head actuator 13) is driven by a control current (VCM current) supplied from the VCM driver 17. In the present embodiment, the SPM driver 16 and the VCM driver 17 are realized by a driver IC 18 integrated on a single chip. A value (control amount) for determining a control current supplied from the SPM driver 16 to the SPM 14 and from the VCM driver 17 to the VCM 15 is determined by the CPU 25 and is converted into a D / A (digital / analog) converter (D / A) is given via 18a and D / A converter 18b.
[0023]
The head 12 seeks and positions on the target track, and then scans the track by rotating the disk medium 11. Further, the head 12 sequentially reads the servo data of the servo areas 110 arranged at equal intervals on the track by scanning. The head 12 reads / writes data from / to the target data sector by scanning.
[0024]
The head 12 is connected to a head amplifier circuit (head IC) 19 mounted on a flexible printed wiring board (FPC). The head amplifier circuit 19 controls switching of the head 12 (in accordance with control from the CPU 25), input / output of read / write signals with the head 12, and the like. The head amplifier circuit 19 amplifies an analog output (read signal of the head 12) read by the head 12, and outputs a predetermined signal to write data sent from a read / write circuit (hereinafter referred to as R / W circuit) 20. It is processed and sent to the head 12.
[0025]
The R / W circuit 20 reads a read signal (head read waveform) read from the disk medium 11 by the head 12 and amplified by the head amplifier circuit 19 by an AGC (automatic gain control circuit) amplifier (not shown). An AGC function that amplifies the voltage, a decoding function (read channel) that performs signal processing necessary to decode the read signal amplified by the AGC function into, for example, NRZ code data, and data recording on the disk medium 11 An encoding function (write channel) for performing necessary signal processing, a pulsing function for pulsing the read signal and outputting it as pulsed read data to enable extraction of servo data from the read signal, and the following Servo according to a predetermined timing signal (burst timing signal) from the servo processing circuit 21 And a function of extracting the burst data in over data. The burst data is sent to the CPU 25 via an A / D (analog / digital) converter (A / D) 24 and used for positioning control for positioning the head 12 at the target position of the target track.
[0026]
The servo processing circuit 21 detects a reference signal 113 following the erase area 112 based on the read pulse output from the R / W circuit 20, generates a start bit, and performs various types for acquiring servo data based on the start bit. It has a function of generating a timing signal and a function of extracting a cylinder address in servo data and using it for seek control by the CPU 25. For the various timing signals, in order to make the R / W circuit 20 operate optimally, (1) a servo gate (servo gate signal) that distinguishes the servo area 110 and the user data area 120, and (2) servo There are an AGC / HOLD signal which is a signal for turning on / off the AGC function for setting the AGC amplifier gain of the R / W circuit 20 suitable for data reading, and (3) a burst timing signal indicating the reading timing of burst data. .
[0027]
The servo processing circuit 21 includes a timer 210 used for generating various timing signals based on the start bit.
[0028]
The buffer memory 22 temporarily stores data (write data) transferred from the host (host system) and written to the disk medium 11 and data (read data) read from the disk medium 11 and transferred to the host. Used. The buffer memory 22 is composed of, for example, a RAM (Random Access Memory) as a rewritable memory.
[0029]
The disk controller 23 manages commands (write command, read command, etc.) with the host, data communication, buffer control, and data transfer control with the disk medium 11.
[0030]
The CPU 25 controls the entire apparatus (HDD) in accordance with a control program stored in a flash ROM (Read Only Memory) 26 as a rewritable nonvolatile memory, for example, the cylinder address and R / W extracted by the servo processing circuit 21. The head 12 seek / position control based on the burst data extracted by the circuit 20, read / write control by the disk controller 23 in accordance with a read / write command from the host, and the like are executed. A RAM 27 that provides a work area for the CPU 25 is connected to the CPU 25. Note that a flash ROM (hereinafter referred to as FROM) 26 and a RAM 27 may be built in the CPU 25.
[0031]
Next, the operation of the disk device of FIG. 1 will be described.
[0032]
First, it is assumed that the servo data recorded in the servo area 110 on the disk medium 11 is read by the head 12. The head read waveform (read signal) of the servo data read by the head 12 is amplified by the head amplifier circuit 19, further amplified to a constant voltage by the AGC amplifier by the R / W circuit 20, and then pulsed.
[0033]
The servo processing circuit 21 detects the reference signal 113 following the erase area 112 of the servo area 110 from the data of the read signal (head read waveform) pulsed by the R / W circuit 20, and generates a start bit. Various timing signals such as a servo gate, an AGC / HOLD signal, and a burst timing signal are generated that represent timings for reading various data in the servo data with reference to the start bit.
[0034]
The servo processing circuit 21 extracts the cylinder code in the address / burst area 114 from the head read waveform data pulsed by the R / W circuit 20 based on the start bit, and sends it to the CPU 25.
[0035]
The R / W circuit 20 performs AGC gain adjustment based on information in the AGC area 111 by using the AGC function at the timing of the AGC / HOLD signal generated by the servo processing circuit 21. In addition, the R / W circuit 20 performs signal processing necessary for decoding, for example, NRZ code data on the head read waveform from the user data area 120 at the timing of the servo gate generated by the servo processing circuit 21. Further, the R / W circuit 20 extracts burst data for the head read waveform from the servo area 110 (internal address / burst area 114) in accordance with the burst timing signal generated by the servo processing circuit 21. This burst data is converted into a digital value by the A / D converter 24 and sent to the CPU 25.
[0036]
The CPU 25 specifies the current position (track position) of the disk medium 11 of the head 12 from the cylinder address extracted by the servo processing circuit 21, and calculates a control amount corresponding to the difference from the target track. Then, the CPU 25 provides the calculated control amount to the VCM driver 17 via the D / A converter 18b, and performs seek control to move the head 12 to the target track by controlling the drive of the VCM 15 (having the head actuator 13). .
[0037]
When the CPU 25 seeks the head 12 to the target track, the CPU 25 calculates a positioning error from the target position of the target track based on burst data extracted by the R / W circuit 20 and sent via the A / D converter 24. Then, the control amount is calculated from the positioning error, and the VCM 15 (the head actuator 13) having the control amount is driven and controlled by the control amount, thereby performing positioning control (on-track control) for positioning the head 12 at the target position.
[0038]
Here, the servo processing circuit 21 generates various timings for reading servo data (necessary for seek / positioning control by the CPU 25), that is, timings for extracting cylinder addresses, burst data, etc. in the servo data. Specific operations for generating signals, servo gates, AGC / HOLD signals, and the like will be described with reference to the timing charts of FIGS. 4 to 6 and the flowcharts of FIGS. .
[0039]
Conventionally, when the servo processing circuit 21 detects a reference signal (113) following the erase area (112) as shown in FIG. 4, it generates a signal called a start bit and starts the internal timer 210 (step S21, S22).
[0040]
When the timer value of the internal timer 210 reaches a preset value t1 (YES in step S23), the magnetic head reaches the data area (120) from the servo area (110) by the rotation of the magnetic disk. The servo gate is changed from a high level (set (Hi) state) to a low level (reset (Lo) state) (steps S23 and S24).
[0041]
Then, the servo gate is set to the high level (set (Hi) state) at the time point t2 when the servo area arrives again (YES in step S25) after passing the user data area (120). Furthermore, the AGC operation of the R / W channel is turned on in the servo unit (the AGC / HOLD signal is set to a high level (set (Hi) state). If the AGC operation is turned on in the erase area, the AGC gain increases. At a timing t3 before the erase area, AGC / HOLD is set to a low level (hold (Lo) state) (YES in step S27, S28) The R / W channel set to the optimum gain in the AGC area is the following reference. Signals, address signals, etc. can be read correctly.
[0042]
When the reference signal is detected again and a start bit is generated, the internal counter is reset and restarted. (This operation is shown in a flowchart in FIG. 8.)
However, when performing a seek operation with head switching, the timing of the data to be read is shifted if there is a positional shift due to an attachment error during manufacturing between the head before switching and the head after switching. As shown in FIG. 5, the case where the head after switching is delayed as compared with the head before switching is described as an example.
[0043]
t1, t2, and t3 are the same as those in FIG. 4, and are normal timings before switching the head. Since the servo mark (reference signal) has already been detected before the head switching, the servo mark (reference signal) is switched at the timings t1, t2, and t3 preset by the head before switching. However, there is a misalignment between the heads before and after switching due to mounting errors during manufacturing. In practice, data cannot be correctly reproduced unless t1 is t4, t2 is t5, and t3 is t6. It will be.
[0044]
If the timing before switching is used as it is, there is a possibility that the address cannot be taken to the end, and it is not adjusted to the correct gain because the AGC gain is adjusted outside the AGC area, and the servo mark (reference signal) is not The possibility that it cannot be detected increases.
[0045]
In the next sector, the timing based on the servo data interval in the previous sector is used as it is, so that t4 = t1, t5 = t2, t6 = t3, and AGC is set after entering the AGC area. Therefore, the AGC gain cannot be correctly adjusted, and the start bit is also lost in this sector.
[0046]
Even if head switching occurs in this way, if the timing of generating internal signals is simply switched over time, the timing will be repeated even if the timing is unexpected even once. May occur.
[0047]
Therefore, in the embodiment of the present application, processing as shown in the timing chart shown in FIG. 6 and the flowchart shown in FIG. 7 is executed.
[0048]
It is determined whether or not the head is switched during the head seek (step S3). If the head is switched (YES in step S3), use of the servo data interval immediately before the head switching is stopped and the servo gate is raised. By setting the level state (set (Hi) state) and keeping AGC in the hold state (hold (Lo) state), the start bit can be detected immediately after the head is switched, and the timer is cleared. Until the time point, the counted inappropriate count value is reset to return to a normal state (step S4).
[0049]
A conventional processing flow will be described with reference to FIG.
[0050]
These are processes performed for each sector and are repeated.
[0051]
First, the timer value is initialized (step S21).
[0052]
When the start bit is detected (NO in step 22), when t1 has elapsed from the start bit detection (YES in step S23), the servo gate is reset (set to the Lo state) to reach the data area from the servo area. (Step S24). After that, when t2 from the start bit (YES in step S25), the servo gate for reaching the servo area is set again (in the Hi state), and at the same time, the AGC is set to adjust the gain in the AGC area. Set (set to Hi state) (step S26). When t3 elapses from the start bit (YES in step S27), the AGC area is passed, so the AGC is held (step S28).
[0053]
Next, the processing flow of the present embodiment will be described with reference to FIG.
[0054]
The process newly added to the flow of FIG. 6, which is the prior art, is a process in the case where the start bit cannot be detected due to missing start bit or timing deviation due to head switching. If the presence / absence / start bit detection is not detected within the predetermined time (timeout occurs) (YES in step S3), the servo gate is set, the AGC is held, and the start bit can be always detected. At the same time, by resetting the timer (step S4), the count in the next sector is not affected by the previous count, and the servo data can be prevented from being taken in for an unexpected reason. .
[0055]
In this embodiment, the head switching is taken as an example. However, the same applies when the start bit is not found. From the time when the start bit is not found and a timeout (a predetermined time elapses) is reached. It will be delayed compared to when it can be detected. In addition, even when the start bit is mistakenly detected in another place, the start bit may be shifted and the same phenomenon as when the head is switched may occur.
[0056]
The possibility that the start bit is erroneously detected in another place must be detected after the AGC area, so it is difficult to think in normal operation, and is generally not high. However, in order to increase the efficiency of servo control, if the start bit is not in the start-up state, the error tolerance is switched so that it can be detected even if the start bits do not match at all, that is, up to about one bit error. For this reason, there is a possibility that the start bit detection timing is delayed, the burst data is erroneously detected as the start bit, and the start bit can be taken at another place.
[0057]
Even in such a case, as described above, when the start bit cannot be detected, when a timeout is detected (YES in step S3), the servo gate is forcibly set (in the Hi state) and the AGC is in the hold state. By leaving (Lo state), the start bit can always be detected. Here, by resetting the timer (step S4), the count in the next sector can be prevented from being affected by the previous count, and the servo data can be prevented from being taken in for an unexpected cause. .
[0058]
【The invention's effect】
As described above in detail, according to the present invention, the timing for servo data reading is cleared when the start bit is erroneously detected, the start bit is missing, or when the servo data interval is wrong during head switching. Then, by stopping the timing generation by the time interval one sample before until the next servo data interval can be correctly obtained, it is possible to prevent the start bit from being lost and the head positioning control from being disabled.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a magnetic disk device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a format example of the disk medium 11 in FIG. 1 and a locus of a head 12 during seek.
3 is a conceptual diagram showing a format example of a servo area 110 in FIG.
FIG. 4 is a timing chart for explaining the relationship between a head readout waveform at the time of head positioning and various timings for servo data reading.
FIG. 5 is a timing chart for explaining problems of the conventional timing in the embodiment.
FIG. 6 is a timing chart for explaining the relationship between a read waveform at the time of head positioning and various timings for servo data reading in an embodiment of the present invention.
FIG. 7 is a flowchart for explaining a generation operation of servo data reading timing in the embodiment;
FIG. 8 is a flowchart for explaining a conventional generation operation of servo data reading timing.
[Explanation of symbols]
11 ......... Disc medium
12 ……… Head
13 ……… Head actuator
14 ......... SPM (spindle motor)
15 ... VCM (voice coil motor)
17 ... VCM driver
20: R / W circuit (read / write circuit)
21 ... Servo processing circuit (timing generation circuit)
25 ... …… CPU
26 .... FROM (flash ROM, storage means)
110 …… Servo area
111 …… AGC area
112 …… Erase area
113 …… Reference signal area
114 …… Address / burst area
120 …… User data area
210 …… Timer (time measuring means)

Claims (4)

A timer, a count value holding means for holding a count value generated by the timer, and a timing generation means for generating a servo information reading timing signal based on the time count value from the previous sector counted by the timer In sector servo type magnetic disk drive,
Detection means for detecting the presence or absence of head switching;
When the detecting means detects the switching of the head, the generation of the next servo information reading timing signal based on the servo information reading timing one sample before is stopped, and a servo gate for reading the next servo information is set. set, and a magnetic disk device characterized by having a control means to an automatic gain control which holds the amplitude value of the read information in a predetermined width on hold. A timer, a count value holding means for holding a count value generated by the timer, and a timing generation means for generating a servo information reading timing signal based on the time count value from the previous sector counted by the timer In sector servo type magnetic disk drive,
Detection means for detecting the presence or absence of head switching;
When the detecting means detects the switching of the head, the servo gate for reading the next servo information is set, the automatic gain control for holding the amplitude value of the read information within a predetermined width is set to the holding state, and the timer is reset. And a control means for controlling the magnetic disk drive. A timer, a count value holding means for holding a count value generated by the timer, and a timing generation means for generating a servo information reading timing signal based on the time count value from the previous sector counted by the timer a control how the magnetic disk device of sector servo system,
Detecting the presence or absence of switching of f head,
When detecting the switching of heads, one sample before on the basis of the detection intervals of the servo data stop the timing generation by the step of generating the next servo data detection timing, sets the servo gate for reading the next servo information And a timing generation method for servo information reading of a magnetic disk device, comprising: setting an auto gain control for holding an amplitude value of read information within a predetermined width . A timer, a count value holding means for holding a count value generated by the timer, and a timing generation means for generating a servo information reading timing signal based on the time count value from the previous sector counted by the timer a control how the magnetic disk device of sector servo system,
Detecting the presence or absence of switching of f head,
When a head change is detected, a servo gate for reading the next servo information is set, an automatic gain control for holding the amplitude value of the read information within a predetermined width is set to a holding state, and the timer is reset. control how the magnetic disk device, characterized in that.

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