JP2004127512A - Disk storage device and compensating method for deviation of a position of servo information - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable compensating discontinuity of servo information at the time of switching a head or the like. <P>SOLUTION: A servo processing circuit 21 generates an interruption signal with timing at which a servo mark is detected by a R/W channel 20. A CPU 24 starts interruption processing in accordance with this interruption signal, and performs servo control using either of a head position (calculated head position) calculated from a position information detected by the R/W channel 20 or this time head position (prediction head position) predicted from position information detected by the servo detecting means the previous time. Then, the CPU 24 switches such decision conditions that which head position is used the calculated head position or the prediction head position depending on the case in which the number of times of interruption from a head switching start time between at least different disks is within the prescribed number of times or the case except the above. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a disk storage device having a plurality of disks in which servo information is recorded in advance, and particularly to a disk storage device and a storage device suitable for compensating for discontinuity of servo information at the time of head switching or the like. The present invention relates to a displacement compensation method.

In a disk storage device using a disk as a storage medium, for example, a magnetic disk device, it is common to seek a head to a target track based on servo information recorded in advance on the disk and position the head within a target range of the track. It is.

Conventionally, servo information is written on a disk by assembling a head and a disk on which a disk is mounted (hereinafter referred to as an HDA), and then setting the HDA in a servo writing device called a servo track writer (STW). This was performed using the head of the HDA itself. However, this method is inefficient.

Therefore, in recent years, servo writers stack disks of a plurality of magnetic disk devices (HDAs) and apply servo information to each of the disks by using a dedicated head for writing servo information provided at each stack position. Information is to be written. By applying this servo information writing method (hereinafter, referred to as a pre-servo method), the efficiency of writing servo information to each disk is improved.

By the way, the magnetic disk device has a read / write (R) for executing various signal processes such as an A / D (analog / digital) conversion process for a read signal by a head, a write data encoding process, and a read data decoding process. / W) IC (R / W channel) is provided. This read / write IC has a function of reading (detecting) servo information. The servo information includes data such as a servo mark, a servo sector address, a cylinder address (cylinder code), and burst data. Therefore, conventionally, in order to read the servo information by the read / write IC, it was necessary to supply various timing signals to the read / write IC.

Therefore, in recent read / write ICs, only the timing of the servo gate is given due to the enhancement of functions with the improvement of the integrated circuit technology, and all the various timings necessary for reading the servo information are synchronized with the timing of the servo gate. It can be generated internally. Such a system in which the read / write IC can read the servo information only at the timing of the servo gate is called a synchronous servo system. In a magnetic disk device to which the synchronous servo system is applied, a servo gate provided to a read / write IC is generated by a servo processing circuit constituted by an ASIC (Application Specific Integrated Circuit).

As described above, in the pre-servo method in which a plurality of disks are stacked on the servo writer and servo information is written on each disk, the efficiency of writing servo information on each disk is improved. However, when an HDA is assembled using a plurality of disks on which the servo information is written and mounted on a magnetic disk device, there is a possibility that the servo position between the disks is physically shifted in the circumferential direction and the radial direction of the disks. .

On the other hand, in the magnetic disk drive to which the synchronous servo system is applied, it is necessary to synchronize the timing of starting the servo gate with the servo position. However, when the servo position is physically shifted between the disks due to the application of the pre-servo method, a shift occurs between the servo gate timing and the actual servo position when the head is switched. For this reason, conventionally, there is a problem that the servo gate timing does not match at the time of head switching or the like, and the seek time is extended, or the servo gate timing is erroneously caused by a missing servo pulse or an erroneous servo detection, resulting in a decrease in seek performance. Was.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has as its object to compensate for discontinuity of servo information at the time of head switching or the like and to minimize performance degradation at the time of head switching or the like. It is an object of the present invention to provide a storage device and a method for compensating for a displacement of servo information.

In the disk storage device according to one aspect of the present invention, servo information including position information, and servo information including a unique servo mark for identifying the servo information is previously recorded at equal intervals on the same circumference. A plurality of disks provided with the recording surfaces described above, a head provided for the respective recording surfaces of the plurality of disks and used for read / write for the corresponding disks, and a disk provided by the head A servo detecting means for detecting the servo mark and the position information from the read information read from the CPU, an interrupt generating means, and a control means.

(4) The interrupt generation means generates an interrupt signal at a timing when the servo mark is detected by the servo detection means. The control means starts interrupt processing in response to the interrupt signal, and calculates a head position (calculated head position) calculated from the position information detected by the servo detection means, or a position previously detected by the servo detection means. The servo control is executed using one of the current head position (predicted head position) predicted from the information. Here, the control means determines whether to use the calculated head position or the predicted head position as a condition for determining whether at least the number of times of interrupt processing from the start of head switching between different disks is within a specified number of times or not. Switch between and.

In the disk storage device having such a configuration, the condition for determining whether to use the calculated head position or the predicted head position for the servo control is that at least the number of interrupt processes from the start of head switching between different disks is within the specified number. And the other cases, that is, the case where (the recording position of) the servo information is discontinuous and the case where it is not. As a result, even if the servo information is discontinuous, the servo control is performed using the information of the head position suitable for the state, that is, the discontinuity of the servo information at the time of head switching (particularly, the discontinuity in the disk radial direction). ) Can be compensated.

According to the present invention, which of the head position calculated from the position information detected by the servo detection means or the current head position predicted from the position information previously detected by the servo detection means is used for the servo control. By switching the determination condition between when servo information is discontinuous, such as when switching heads, and when it is not, the discontinuity of servo information when switching heads can be compensated, and performance when switching heads, etc. Can be minimized.

Hereinafter, an embodiment in which the present invention is applied to a magnetic disk drive will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a magnetic disk drive according to one embodiment of the present invention.
In the magnetic disk device (hereinafter referred to as HDD) in FIG. 1, reference numerals 11a and 11b are disks (magnetic disk media) as recording media on which data is magnetically recorded. On each recording surface side of the disk 11i (i = a, b), a head (magnetic head) 12 used for data writing (data recording) on the disk 11i and data reading (data reproduction) from the disk 11i is provided. Each is provided. Here, it is assumed that servo information is recorded in advance on the two disks 11a and 11b by a pre-servo method. The number of disks need not be two, but may be any HDD in which a plurality of disks are stacked.

As shown in FIGS. 2A and 2B, a plurality of servo areas 110 are arranged radially from the center of the disk and at equal intervals in the disk circumferential direction on each recording surface of each of the disks 11a and 11b. . In the servo area 110, servo information used for seek / positioning control and the like of the head 12 is recorded. A large number of concentric tracks 111 are also formed on each recording surface of each of the disks 11a and 11b. A user data area 112 is provided between the servo areas 110, and a plurality of data sectors are arranged in the data area 112.

As described above, servo information is recorded on the disks 11a and 11b by the pre-servo method. Therefore, it is assumed that the position of the servo area 110, that is, the servo position, is physically shifted in the disk circumferential direction between the disks 11a and 11b as shown in FIGS. 2 (a) and 2 (b). Further, the position of the head 12 in the disk radial direction, that is, the cylinder position and the position error may be shifted between the disks 11a and 11b.

2) The servo area 110 has a preamble area 113, a servo mark area 114, a gray code area 115, and a burst area 116, as shown in FIG. The preamble area 113 includes an AGC (Automatic Gain Control) area in which a signal of a certain frequency used for stabilizing the amplitude of the signal is recorded, and an erase unit. In the servo mark area 114, a unique mark (servo mark) for identifying (servo information recorded in the servo area) is recorded. Here, the servo mark is "14h" (h at the end indicates hexadecimal representation). In the gray code area 115, an address (servo sector address) unique to the corresponding servo area and a cylinder address (cylinder code) of the corresponding track are recorded in gray code. In the burst area 116, burst data (PES information) which is a position error signal (Positional Error Signal) for indicating a position error in a cylinder indicated by a cylinder address in the gray code area 115 by a waveform amplitude is recorded. . That is, the servo information recorded in the servo area 110 includes a servo mark, a servo sector address, a cylinder address as position information, and burst data.

Referring again to FIG. 1, the disk 11 i (i = a, b) is rotated at a high speed by a spindle motor (hereinafter referred to as SPM) 13. The head 12 is attached to an actuator (rotary head actuator) 14 as a head moving mechanism, and moves in the radial direction of the disk 11i according to the rotation (angular rotation) of the actuator 14. Thus, the head 12 is sought and positioned on the target track. The actuator 14 has a voice coil motor (hereinafter, referred to as VCM) 15 as a drive source of the actuator 14, and is driven by the VCM 15. A ramp mechanism (not shown) having a head retreat area (parking area) for each recording surface for retracting each head 12 when the HDD transitions to the idle state is provided on the outermost peripheral side of the disks 11a and 11b. ) Is arranged.

The SPM 13 is driven by a drive current (SPM current) supplied from the SPM driver 16. The VCM 15 is driven by a drive 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 one chip. A value (operating amount) for determining a drive current supplied from the SPM driver 16 to the SPM 13 and a drive current supplied from the VCM driver 17 to the VCM 15 are determined by the CPU 24, and are set to a D / A (digital / analog) converter (D / A A) It is provided via a D / A converter 18b.

The head 12 is connected to a head IC 19 mounted on a flexible printed wiring board (FPC).
The head IC 19 has a read amplifier that amplifies a read signal read by the head 12 and a write amplifier that converts write data into a write current. The head IC 19 is connected to a read / write IC (hereinafter, referred to as R / W channel) 20.

The R / W channel 20 performs various signal processes such as an A / D (analog / digital) conversion process on a read signal, a write data encoding process, and a read data decoding process.

The R / W channel 20 operates according to an operation mode (servo gate control mode) switched and set by the CPU 24. The operation mode includes a start-up mode (initial mode) corresponding to a servo information position interval, that is, a servo interval is shifted, and a normal mode (normal servo gate control mode) corresponding to a case where the servo interval is not shifted. There are two types. The R / W channel 20 has a function of generating an internal timing signal for detecting data constituting servo information in accordance with the rising (leading edge) timing of the servo gate SVGATE from the servo processing circuit 21 in the normal mode. And a function of detecting each data constituting servo information in accordance with the internal timing signal, that is, a servo mark, a gray code, and burst data. In the start-up mode, the R / W channel 20 starts an operation of searching for servo information and detecting a servo mark from the rising edge of the servo gate SVGATE, and when a servo mark is detected, the subsequent operation is performed at a timing determined by the detection timing. It has a function to detect gray code and burst data.

The R / W channel 20 classifies the quality of the servo mark detected by itself according to the detection level, that is, whether the servo mark is completely recognized as a servo mark or almost recognized as a servo mark. The servo mark quality information indicating the quality is serially transferred to the servo processing circuit 21 in synchronization with the servo mark detection, and the gray code and burst data (burst data after A / D conversion) detected after the servo mark are also transmitted. The servo processing circuit 21 has a function of performing serial transfer. Here, the servo mark quality information transferred from the R / W channel 20 to the servo processing circuit 21 is composed of 4 bits, and the first bit is “1”. The start bit “1” indicates the start of the transfer of the servo information from the R / W channel 20 to the servo processing circuit 21 (here, the gray code and the burst data following the servo mark).

The servo processing circuit 21 determines the start of the servo information transfer based on the first bit “1” of the servo mark quality information transferred from the R / W channel 20, and decodes the 4-bit quality information starting from the first bit, When the R / W channel 20 indicates that the servo mark (“14h” following several AGC bits) has been correctly detected, a function of outputting a start bit SB indicating a reference position of the servo area, A function of generating the servo gate SVGATE based on the result of the time measurement started at the timing of the bit SB. The servo processing circuit 21 also decodes the Gray code transferred from the R / W channel 20 to convert the Gray code into a servo sector address and a cylinder address, and converts these servo sector address, cylinder address and burst data into a servo register 221 described later. Has the function of holding

FIG. 3 shows the block configuration of the servo processing circuit 21. The servo processing circuit 21 is configured by an ASIC (Application Specific Integrated Circuit) such as a gate array. The servo processing circuit 21 detects that the servo mark (“14h”) in the servo information has been correctly detected in the R / W channel 20 by decoding the servo mark quality information transferred from the R / W channel 20. And a start bit detector (SB detector) 210 for outputting a start bit SB. Here, the fact that the servo mark (“14h”) is correctly detected may be referred to as “the start bit SB has been detected”.

The servo processing circuit 21 also has a main counter 211 for measuring the servo interval in synchronization with the clock CLK based on the start bit SB, and a servo interval (actual servo interval) measured by the main counter 211. The real servo interval register 212 includes a synchronization circuit 213 that generates a timing for holding the real servo interval in the real servo interval register 212 from the start bit SB and the clock CLK.

The servo processing circuit 21 also has a start bit continuous detector 214 for detecting that the start bit SB has been detected a plurality of times, for example, twice in succession. The start bit continuous detector 214 detects a missing start bit SB (SB missing detector) 215 from the value of the main counter 211 and the number of times the start bit SB is continuously detected in the startup mode. , And an OR gate (OR) 217 that generates a signal for clearing the value of the SBCNT 216. The OR gate 217 has a signal 218 indicating that the start bit SB missing has been detected by the SB missing detector 215, a signal 219 indicating that the clearing of the SBCNT 216 has been instructed by the CPU 24, and a calculation unit 226 described later. The signal 220 indicating the abnormal servo gate timing and the state signal of the startup mode flag SUMF are input.

The servo processing circuit 21 also has a servo register 221 for holding a servo sector address, a cylinder address, and burst data, and a mode selection register (RFLDFG) 222. The mode selection register 222 is used to set a flag (startup mode flag) SUMF for mode switching regarding servo gate control in the servo processing circuit 21. There are two types of modes that can be switched by the flag SUMF: the start-up mode (initial mode) and the normal mode.

The servo processing circuit 21 also includes a servo gate set register 223 and a servo gate reset register 224 for forcibly turning on / off the servo gate SVGATE by the CPU 24, and a start bit counter for forcibly clearing the start bit counter 212. And a clear register (SBCNT clear register) 225.

The servo processing circuit 21 also provides the R / W channel 20 with an arithmetic unit 226 that calculates a correction value required to correct the servo gate timing reflecting the servo interval variation based on the value of the actual servo interval register 212. It has a servo gate generator 227 for generating a servo gate SVGATE, and an interrupt generator (EOS generator) 228 for generating an interrupt signal (servo interrupt signal) EOS for each servo to the CPU 24. The servo gate generator 227 generates the servo gate SVGATE based on the calculation result of the arithmetic unit 217 in the normal mode, and generates the servo gate SVGATE according to the instruction of the CPU 24 in the start-up mode. Therefore, the servo gate generator 227 is configured so that the servo gate SVGATE is not turned on / off by the value of the main counter 211 in the startup mode. The EOS generator 228 generates a servo interrupt signal EOS according to the start bit SB. The EOS generator 228 also generates a servo interrupt signal EOS according to the value of the main counter 211. Note that the EOS generator 228 may generate the servo interrupt signal EOS only in response to the start bit SB.

Referring again to FIG. 1, the buffer memory 22 stores data (write data) transferred from the host (host system) to be written to the disk 11i and data (read data) read from the disk 11i and transferred to the host. Used for temporary storage. The buffer memory 22 is composed of, for example, a RAM (Random Access Memory) as a rewritable memory.

The disk controller 23 controls commands (write command, read command, etc.) with the host, data communication, control of the buffer memory 22, data transfer control with the disk 11i, and the like.

The CPU 24 controls the entire device (HDD) according to a control program (hereinafter, referred to as FW (Firmware)) stored in a flash ROM (Read Only Memory) (hereinafter, referred to as FROM) 25 as a rewritable nonvolatile memory, for example. , Read / write control by the disk controller 23 in accordance with a read / write command from the host, and control for seeking and positioning the head 12 to the target track. For this seek / positioning control, the CPU 24 acquires the cylinder address and burst data held in the servo register 213 of the servo processing circuit 21 by reading the register. In addition to the FW, the FROM 25 stores in advance parameter values, which will be described later, necessary for determining whether to apply the predicted value of the head position at the time of head switching. The CPU 24 is connected to a RAM 26 that provides a work area and the like for the CPU 24. Note that a configuration in which the FROM 25 and the RAM 26 are built in the CPU 24 is also possible.

Next, the operation of the HDD of FIG. 1 will be described.
First, an overview of servo gate control in the HDD of FIG. 1 will be described.

In this embodiment, servo information is recorded on the two disks 11a and 11b mounted on the HDD in FIG. 1 by a pre-servo method. Therefore, the physical servo position may be shifted between the disks 11a and 11b as shown in FIGS. That is, the servo gate timing may not be synchronized between the disks 11a and 11b. Therefore, in the present embodiment, assuming that the servo position is shifted between the disks 11a and 11b, servo gate control for absorbing the shift is performed. This control is basically performed by (the ASIC for realizing) the servo processing circuit 21.

To determine the timing of the servo gate, it is necessary to know the interval between two consecutive physical servo positions, that is, the servo interval. Therefore, the servo processing circuit 21 detects the servo mark twice in succession to obtain the initial value of the servo interval for the first time, and can shift from the startup mode to the normal mode. In the normal mode, the servo gate SVGATE is automatically generated by the servo processing circuit 21 (the servo gate generator 227 therein) according to the servo interval measured by the servo processing circuit 21.

On the other hand, when the head 12 is moved from the ramp mechanism onto the disk 11i during a first seek, when a head is switched (particularly, when a head is switched between different disks), or when a servo mark detection error occurs continuously, a servo When the gate timing is lost, that is, when the servo gate timing is shifted, it is determined that the condition for switching to the start-up mode is satisfied by the processing (FW processing) of the CPU 24 according to the control program stored in the FROM 25 and the servo processing is performed. The circuit 21 is switched to the start-up mode. In the start-up mode, the servo gate SVGATE is generated from the servo processing circuit 21 (the servo gate generator 227 therein) at a timing determined by the processing (FW processing) of the CPU 24.

Next, details of the servo gate control in the HDD of FIG. 1 will be described with reference to the timing charts of FIGS. 4 and 5 and the flowchart of FIG.

In the normal mode, the R / W channel 20 detects each data constituting the servo information in synchronization with the rising timing of the servo gate SVGATE automatically generated by the servo gate generator 227 in the servo processing circuit 21. Generates an internal timing signal. The R / W channel 20 reads each data constituting servo information from the read data read by the head 12 and amplified by the head IC 19 in accordance with the internal timing signal, that is, servo marks, gray codes, and burst data. Is detected. As described above, in the normal mode, the R / W channel 20 detects each data in the servo information by the synchronous servo method.

On the other hand, in the start-up mode (initial mode), the R / W channel 20 starts a search operation described below from the time when the servo gate SVGATE generated by the servo gate generator 227 rises at the timing specified by the CPU 24. That is, the R / W channel 20 starts a search operation for monitoring read data read by the head 12 and amplified by the head IC 19 and detecting a servo mark from the read data. If the servo mark is detected within a predetermined period, the R / W channel 20 detects the subsequent gray code and burst data at a timing determined by the timing of the servo mark detection. Classifies the servo mark detected by itself into quality according to the detection level, and serially transfers 4-bit servo mark quality information indicating the quality to the servo processing circuit 21. The first bit (first bit) of the 4-bit servo mark quality information is “1”, which indicates the start bit SB. The second bit of the servo mark quality information is "1" indicating that the servo mark was detected, and "0" indicating that the servo mark was not detected. The third bit of the servo mark quality information indicates the quality of the detected servo mark. "0" indicates high quality (for example, an error of 1 bit or less), and "1" indicates low quality (for example, an error of 2 bits or more). Is shown. The description of the fourth bit of the quality information is omitted because it is not directly related to the present invention. When the R / W channel 20 detects a gray code and burst data following the servo mark following the servo mark, the R / W channel 20 serially transfers the detected data to the servo processing circuit 21. However, the burst data is A / D converted and transferred.

(4) The SB detector 210 in the servo processing circuit 21 decodes 4-bit servo mark quality information starting from logic "1" in data serially transferred from the R / W channel 20. When the decoded quality information is a predetermined 4-bit value, for example, “1101”, the SB detector 210 indicates that the quality information is high quality, and the servo mark is correctly detected in the R / W channel 20. As a result, a start bit SB is output each time. When the quality information is “110 ×” or “11xx” (× may be “0” or “1”), the start bit SB may be output from the SB detector 210. Absent.

(4) The main counter 211 in the servo processing circuit 21 performs a counting operation at the timing of the internal clock CLK. When the start bit SB is output from the SB detector 210, the main counter 211 stops the counting operation. At this time, the count value of the main counter 211 is latched in the actual servo interval register 212 at the timing generated by the synchronization circuit 213, that is, at the timing of the next clock CLK after the start bit SB is output from the SB detector 210. You. Then, the count value of the main counter 211 is reset at the timing of the next clock CLK, and the counting operation is restarted again at the timing of the clock CLK. Therefore, the actual servo interval register 212 holds the count value between the two start bits SB, that is, the measured value of the actual servo interval.

The EOS generator 228 in the servo processing circuit 21 uses the start bit SB output from the SB detector 210 in response to the servo mark detection as long as the servo mark is correctly detected by the R / W channel 20. After a certain period of time, a servo interrupt signal EOS to the CPU 24 is output.

The CPU 24 performs a servo interrupt process (FW process) according to the flowchart of FIG. 6 in accordance with the servo interrupt signal EOS from the EOS generator 228 as follows.
First, the CPU 24 determines whether the operation mode of the servo processing circuit 21 (and the R / W channel 20) is the startup mode or the normal mode (step S1).

If the mode is the normal mode, the CPU 24 determines whether or not the condition for switching to the startup mode is satisfied (step S2). Here, it is assumed that the condition for switching to the start-up mode is satisfied when the servo gate timing is lost, such as at the time of a first seek, at the time of head switching, or when a servo mark detection error occurs continuously. .

When the condition for switching to the start-up mode is satisfied, the CPU 24 sets a valid (here, logic “1”) start-up mode flag SUMF in a mode selection register (RFLDFG) 222 in the servo processing circuit 21, thereby setting the relevant servo. The processing circuit 21 is set to the start-up mode (step S3). Further, the CPU 24 determines that the servo gate timing does not match the actual position of the servo area 110 on the disk 11i, that is, the physical servo position until the count value of the SBCNT 216 in the start bit continuous detector 214 becomes “2”. , R / W channel 20 are also set to the startup mode (initial mode) (step S4). Accordingly, in the R / W channel 20, an operation of searching for servo information and detecting a servo mark is performed. Here, step S4 may be executed prior to step S3.

After executing steps S3 and S4, the CPU 24 controls the servo gate generator 227 by accessing the servo gate set register 223 after, for example, a second fixed time based on the rising edge (leading edge) of the servo interrupt signal EOS. Then, the servo gate SVGATE is turned on (step S5). As a result, in the R / W channel 20, the servo information is detected in the startup mode, and the servo mark quality information, the gray code, and the burst data (PES information) are serially transferred to the servo processing circuit 21 sequentially. A decoder (not shown) in the servo processing circuit 21 decodes the Gray code transferred from the R / W channel 20 and converts the Gray code into a servo sector address and a cylinder address. These servo sector addresses, cylinder addresses, and burst data are held in the servo register 221. The CPU 24 performs positioning control for positioning the head 12 in a target range of a target track based on the cylinder address and the burst data held in the servo register 221. Details of this positioning control will be described later.

In the servo processing circuit 21, when the mode is switched to the startup mode as a result of setting the startup mode flag SUMF of logic "1" in the mode selection register (RFLDFG) 222, the state signal of the startup mode flag SUMF is output via the OR gate 217. Is input to the clear terminal CLR of the SBCNT 216. Thereby, the SBCNT 216 is cleared, and the count value becomes “0”. Thereafter, the SBCNT 216 is incremented by one each time the start bit SB is detected by the SB detector 210.

In the servo processing circuit 21, the start-up mode continues until the count value of the SBCNT 216 becomes "2". In this start-up mode, when the start bit SB is detected by the SB detector 210 and the servo interrupt signal EOS is output from the EOS generator 228 to the CPU 24 in response to the detection of the start bit SB, the CPU 24 starts the servo operation according to the flowchart of FIG. Interrupt processing (FW processing) is performed as follows.
First, since the operation mode of the servo processing circuit 21 (and the R / W channel 20) is the start-up mode (step S1), the CPU 24, for example, performs the first fixed time (for the first time) based on the servo interrupt signal EOS. After a certain time <the second certain time, the servo gate generator 227 is controlled by accessing the servo gate reset register 224 to turn off the servo gate SVGATE (step S6). Thereafter, the CPU 24 turns on the servo gate SVGATE by the servo gate generator 227 by accessing the servo gate set register 223 after the second fixed time based on the servo interrupt signal EOS (step S5). Then, the CPU 24 performs servo control for seeking and positioning the head 12 on the target track based on the servo information detected by the R / W channel 20 while the servo gate SVGATE is on.

Eventually, when the count value of the SBCNT 216 switches from “1” to “2”, that is, when the start bit SB is detected continuously for two servos, the mode selection register (RFLDFG) 222 is reset and held in the register 222. The startup mode flag SUMF is switched to “0”. As a result, the operation mode of the servo processing circuit 21 is automatically switched from the startup mode to the normal mode. The CPU 24 reads the start-up mode flag SUMF held in the mode selection register 222 by FW processing, and detects that the operation mode of the servo processing circuit 21 has been switched to the normal mode. In this case, the CPU 24 switches the operation mode of the R / W channel 20 from the startup mode (initial mode) to the normal mode.

When the count value of the SBCNT 216 becomes “2” and the operation mode of the servo processing circuit 21 is switched to the normal mode, the count operation of the SBCNT 216 is disabled. As a result, the count value of the SBCNT 216 is held at 2 even when the start bit SB is detected by the SB detector 210. The count value of the SBCNT 216 may be cleared to “0” by the CPU 24 accessing the SBCNT clear register 225 and outputting a valid logical “1” signal from the OR gate 217 to the clear terminal of the SBCNT 216. Absent.

By the way, in the start-up mode, the servo mark may not be detected by the R / W channel 20 while the servo gate SVGATE is open under the control of the CPU 24. In this case, servo mark quality information whose second bit is “0”, that is, servo mark quality information indicating that no servo mark was detected is transferred from the R / W channel 20 to the servo processing circuit 21. In this case, the SB detector 210 in the servo processing circuit 21 does not output the start bit SB based on the first bit of the servo mark quality information. This situation is represented by a start bit SB51 in the timing chart of FIG. In FIG. 5, the start bit SB51 is represented by a broken line, and indicates that the start bit SB is not actually output, that is, the start bit SB is not detected.

By the way, when the start bit SB is not detected by the SB detector 210, that is, when the detection of the servo mark fails, the main counter 211 continues the counting operation up to a predetermined upper limit value. Therefore, the missing SB detector 215 compares the count value of the main counter 211 with a predetermined reference value, and determines that the start bit SB is missing when the count value becomes larger than the reference value. As the reference value, a value corresponding to a time sufficient for detecting a servo mark is used.

In this case, the SB missing detector 215 outputs a signal “218” of logic “1” indicating that the start bit SB missing has been detected. This signal 218 is input to the clear terminal CLR of the SBCNT 216 via the OR gate 217. Thereby, the SBCNT 216 is cleared, and the count value becomes “0”. That is, the count value of the SBCNT 216 is cleared to “0” when the start bit SB missing is detected. With this mechanism, the SBCNT 216 in the start bit continuous detector 214 can count the number of start bits SB detected continuously.

In the present embodiment, when the count value of the main counter 211 exceeds a predetermined value, the EOS generator 228 generates and outputs a pseudo servo interrupt signal EOS. Thus, even when the start bit SB is missing, the CPU 24 can perform the FW process as shown in the timing chart of FIG.

Calculator 226 calculates a correction value required to correct the servo gate timing reflecting the servo interval variation, and calculates the servo gate timing using the correction value. The calculation in the calculator 226 is performed regardless of the operation mode of the servo processing circuit 21. However, the operation result is actually used for generating the servo gate SVGATE only in the normal mode. In the start-up mode, the arithmetic unit 226 determines whether the arithmetic result in the arithmetic unit 226 is appropriate. If the operation result in the operation unit 226 is not appropriate, the operation unit 226 outputs a signal 220 of logic “1”. This signal 220 is input to the clear terminal CLR of the SBCNT 216 via the OR gate 217. Thereby, the SBCNT 216 is cleared, and the count value becomes “0”. It should be noted that the validity of the correction value calculated by the arithmetic unit 226 is determined only when the value of the SBCNT 216 becomes “2”, and when the value is not valid, the value of the SBCNT 216 is decremented by one. That is, the value of the SBCNT 216 may be set to “1”.

As described above, in the present embodiment, the start-up mode (first mode) is set when there is a possibility that the timing of the servo gate is shifted, for example, at the time of head switching. In this start-up mode, the R / W channel 20 starts the operation of detecting the servo mark from the read information by monitoring the read information from the time when the servo gate is opened. At the determined timing, the operation of detecting the subsequent position information (cylinder address and burst data) from the read information, that is, the operation of detecting the servo mark and the position information without applying the synchronous servo method is performed. Then, when the start bit continuation detector 214 detects that the servo mark has been continuously detected a plurality of times in the startup mode, that is, when the discontinuity of the servo position is resolved, the mode is switched to the normal mode. In the normal mode, the R / W channel 20 performs an operation of detecting servo marks and position information by a synchronous servo method.

(4) As a result, even if a physical displacement of the servo position occurs at the time of head switching or the like, the displacement can be compensated for, and a decrease in performance at the time of head switching or the like can be minimized.

Here, the calculation of the servo gate timing by the arithmetic unit 226 will be described with reference to FIG. 7 while taking a seek operation for moving the head 12 to a target track on the disk 11i as an example.

Calculator 226 executes three types of calculations for calculating timings SGSTS, SGCLRS, and SGSTS2 as calculations for correcting servo interval fluctuation during the seek operation. The timing SGSTS indicates the timing of opening the next servo gate based on the position of the start bit SB. The timing SGCLRS is a timing used when the start bit SB is missing, and indicates a timing at which the servo gate is closed based on the preceding start bit SB. The timing SGSTS2 is a timing used when the start bit SB is missing, and is a timing at which the servo gate closed at the timing SGCLRS is opened again. Here, the standard timing of opening the servo gate with reference to the start bit SB is SGST, and the standard timing of closing the servo gate is SGCLR. The interval between two consecutive servo areas 110, that is, one servo interval is SMITV. The theoretical count value of the main counter 211 in one servo interval is SMITVS, and the actual count value of the main counter 211 in one servo interval, that is, the value of the real servo interval register 212 is SMITVM. SGST, SGCLR, SMITV, and SMITVS are fixed values.

In this case, the arithmetic unit 226 calculates the deviation DELTAT from the theoretical value of the count value of the main counter 211 in one servo interval as follows: DELTAT = SMITVM-SMITVS (1)
It is calculated by:

The arithmetic unit 226 uses this DELTAT to calculate the timing SGSTS, SGCLRS, SGSTS2 by the following equation: SGSTS = SGST + DELTAT (2)
SGCLRS = SGCLR + SMITVM-SMITVS + SMITV
= SGCLR + DELTAT + SMITV (3)
SGSTS2 = SGST + (SMITVM-SMITVS) * 2
+ SMITV
= SGST + DELTAT * 2 + SMITV (4)
Calculated according to When the start bit SB is first detected at the time of the initial startup, the calculation is performed with SMITVM = 0.

Next, an overview of servo control at the time of head switching in the HDD of FIG. 1 will be described.

Normally, in servo control, based on continuous servo information, a position where servo information that can be obtained next is recorded is predicted from the operation amount. In the case of the conventional method of writing servo information with the head of the HDA, a mechanical deviation such as a carriage deviation between heads is caused by a deviation of a physical servo position including a deviation in a disk radial direction which a mechanical unit has in advance. It corresponds to. Therefore, the continuity of the servo position between the heads, that is, the continuity of the position information is ensured. Due to this continuity, in the seek and positioning (track following) control in the servo interrupt processing by the CPU 24, the position calculated from the cylinder address and the burst data as the position information actually obtained and the predicted position are used. , The reliability of the calculated position can be determined. If it is determined that the calculated position has poor reliability, it is possible to perform high-accuracy servo control by using a predicted value instead of the calculated position.

に 対 し て On the other hand, when the servo information is written by applying the pre-servo method, there is a high possibility that the continuity of the position information is broken between the heads of different disks. In this case, the reliability of the predicted value itself becomes a problem. Therefore, it is necessary to pay attention to the application of the predicted value of the head position when switching the head.

In the present embodiment, regarding the application of this predicted value,
(1) A method of limiting the application of the predicted value of the head position at the time of head switching (2) A method of expanding the applicable range while limiting the application of the predicted value of the head position at the time of switching the head (3) Manufacturing of HDD Sometimes, a difference in position information between the heads is detected, and a dedicated head position predicted value parameter immediately after head switching determined by the difference is stored in the FROM 25, and based on the value of the parameter, the reliability of the calculated position is determined. Either one of the methods for determining the condition (prescribed range) used for the determination of gender is used, or at least two methods are used in combination. By adding an algorithm for applying the head position prediction value at the time of head switching, it is possible to secure the reliability of the acquired head position and to cope with the case where the continuity of position information between heads is lost. Become.

Hereinafter, the servo control to which the above method (1) is applied will be described with reference to the flowchart of FIG.
As described above, the CPU 24 performs the servo interrupt processing according to the flowchart of FIG. 6 according to the servo interrupt signal EOS from the EOS generator 228 in the servo processing circuit 21. The CPU 24 performs servo control for seeking and positioning the head 12 on the target track based on the servo information detected by the R / W channel 20 in the interrupt processing as follows in accordance with the flowchart of FIG. .

First, the CPU 24 reads the cylinder address and burst data (position error data) required for servo control, that is, head position information, from the servo register 221 in the servo processing circuit 21 (step S11). Then, the CPU 24 calculates the current position of the head 12 from the read position information (step S12).

Next, the CPU 24 determines whether or not the number of servo interrupt processes executed since the start of head switching has exceeded a specified number (step S13). If the number of times of servo interrupt processing is equal to or less than the specified number, the CPU 24 determines that the reliability of the predicted value is poor due to the discontinuity of the position information between before and after head switching, and therefore, in step S12. It is determined that the application of the prediction value should be suppressed regardless of the position calculation result. In this case, the CPU 24 calculates an operation amount (VCM operation amount) for determining a drive current required to drive the VCM 15 based on the position information calculated in step S12 (step S14). By setting the calculated operation amount in the VCM driver 17, a drive current of a corresponding magnitude is supplied from the VCM driver 17 to the VCM 15, and the VCM 15 is driven.

On the other hand, if the number of times of servo interrupt processing exceeds the specified number, the influence of the discontinuity of the position information between before and after head switching is reduced, and the reliability of the predicted value is high. Judge. In this case, the CPU 24 determines that the position calculated at step S12 (currently calculated position) is a specified range (normally specified) based on the current head position (predicted value) calculated (predicted) from the previously acquired position information. (Step S15). Here, the normal specified range (first specified range) is a range of ± α based on a predicted value calculated from the previously acquired position information.

If the current calculation position is within the normal specified range, the CPU 24 determines that the reliability of the current calculation position is high and calculates the VCM operation amount based on the calculated position (step S14).

On the other hand, if the current calculation position is out of the normal specified range, that is, despite the fact that the influence of the discontinuity of the position information between before and after head switching is reduced, the current calculation position is reduced. Is outside the normal specified range, the CPU 24 determines that the reliability of the current calculation position is low and applies a predicted value instead of the current calculated position (step S16), and determines the VCM operation amount based on the predicted value. It is calculated (step S14).

As described above, in the present embodiment, among the servo interrupt processes executed after the start of head switching, the application of the predicted value is suppressed in the interrupt process until the number of interrupt processes exceeds the specified number. . Thus, it is possible to prevent an erroneous predicted value from being applied due to the effect of the discontinuity of the head position immediately after the head switching.

Next, servo control to which the above method (2) is applied will be described with reference to the flowchart in FIG.
The CPU 24 reads the head position information from the servo register 221 in the servo processing circuit 21 as in step S11 in FIG. 8 (step S21). Then, the CPU 24 calculates the current position of the head 12 from the read position information (step S22).

Next, the CPU 24 determines whether or not the number of servo interrupt processes executed since the start of head switching has exceeded a specified number (step S23). If the number of times of servo interrupt processing exceeds the specified number, steps S24 to S26 similar to steps S14 to S16 in FIG. 8 are performed.

On the other hand, if the number of times of servo interrupt processing is equal to or less than the specified number, the CPU 24 determines whether or not the position calculated in step S22 (currently calculated position) is within a specified range immediately after head switching (step S27). . Here, the specified range immediately after the head switching (second specified range) is ± β based on the current head position (predicted value) calculated from the previously acquired position information (where β is β> α). ) Range. As is evident, the specified range immediately after the head switching is wider than the normal specified range.

If the current calculation position is within the dedicated range immediately after the head switching, the CPU 24 determines that the reliability of the current calculation position is high and calculates the VCM operation amount based on the calculated position (step S24).

On the other hand, if the current calculation position is outside the specified range immediately after head switching, that is, considering that the number of times of servo interrupt processing is equal to or less than the specified number, the specified range wider than the normal specified range (specified range immediately after head switching) ), The CPU 24 determines that the reliability of the current calculation position is low and applies the predicted value instead of the current calculation position (step S26). The VCM operation amount is calculated based on the predicted value (Step S24).

As described above, in the present embodiment, of the servo interrupt processing executed after the start of head switching, the number of times of the interrupt processing is not more than the specified number (here, about 1 to 3), and is unconditionally set. Instead of applying the predicted value, a dedicated range immediately after head switching that is wider than the normal specified range is used, and the predicted value is not applied only when the current calculated position is within the dedicated specified range. Thus, it is possible to prevent the erroneous predicted value from being applied due to the discontinuity of the head position immediately after the head switching, while expanding the range of application of the predicted value.

Next, servo control to which the above method (3) is applied will be described with reference to the flowchart of FIG. Note that the flowchart of FIG. 10 is not limited to the time of head switching but is common to servo control in servo servo interrupt processing.

First, in the embodiment to which the method (3) is applied, a difference in position information between heads, that is, a difference in head position is detected at the time of manufacturing the HDD in FIG. 1, and a dedicated value immediately after head switching of a value determined by the difference is detected. The head position predicted value parameter (first predicted value parameter) is stored in the FROM 25. The FROM 25 also stores a normal head position prediction value parameter (second prediction value parameter) for the same head (disk surface) that ensures continuity of position information. It is also possible to store these parameters on the disk 11i and load them into the RAM 26 when the HDD is initialized.

The CPU 24 reads the head position information from the servo register 221 in the servo processing circuit 21 as in step S11 in FIG. 8 (step S31). Then, the CPU 24 calculates the current position of the head 12 from the read position information (step S32).

(4) Next, the CPU 24 determines whether or not it is immediately after the head switching (servo interrupt processing) (step S33). If the head has just been switched, the CPU 24 reads a dedicated head position parameter immediately after the head switching from the FROM 25 (step S34). On the other hand, if it is not immediately after the head switching, the CPU 24 reads the normal head position predicted value parameter from the FROM 25 (step S35). It should be noted that instead of determining whether or not the head has just been switched, whether or not the number is equal to or less than a predetermined number of servo interrupt processes may be determined. As is apparent, the case where the predetermined number of times of the servo interrupt process is 1 corresponds to immediately after the head switching.

After executing step S34 or S35, the CPU 24 uses the current head position (predicted value) calculated from the value of the head position predicted value parameter read in step S34 or S35 and the previously acquired position information as a reference. It is determined whether or not the position calculated in step S12 (currently calculated position) is within the specified range (step S36).

If the current calculation position is within the specified range, the CPU 24 determines that the reliability of the current calculation position is high and calculates the VCM operation amount based on the calculated position (step S37).

On the other hand, if the current calculation position is out of the specified range, the CPU 24 determines that the reliability of the current calculation position is low and applies a predicted value instead of the current calculated position (step S38), and based on the predicted value. The VCM operation amount is calculated (Step S37).

As described above, in the present embodiment, a dedicated head position parameter immediately after head switching reflecting the head position difference between the heads is stored in the FROM 25 (nonvolatile storage device), and immediately after head switching, It is determined whether or not the reliability of the head position (currently calculated position) calculated from the currently obtained position information is high using a specified range determined from the value of the parameter and the previously obtained position information. are doing. For this reason, highly accurate determination is possible.

In the embodiment described above, it is assumed that there is a possibility that the servo position (the position of the servo area 110) may physically deviate between the respective heads. Has been described. However, between one head (recording surface) and the other head (recording surface) of the same disk, there is very little possibility that the servo position is physically shifted. Therefore, the above specific processing may be performed only when the head is switched between different disks. In this case, “head switching” in the above embodiment may be read as “head switching between different disks”.

In the above-described embodiment, the case where the present invention is applied to an HDD (magnetic disk device) has been described. However, the present invention is not limited to this, and the present invention relates to a disk storage device other than HDD such as a magneto-optical disk device. Is also applicable.

Note that the present invention is not limited to the above-described embodiment, and can be variously modified in an implementation stage without departing from the scope of the invention.

FIG. 1 is a block diagram showing a configuration of a magnetic disk drive according to one embodiment of the present invention. 1 shows the concept of the format of each of the disks 11a and 11b, the physical displacement of the position of the servo area 110 recorded on each of the disks 11a and 11b, and the concept of the data format of the servo area 110. FIG. FIG. 2 is a block diagram illustrating a configuration of a servo processing circuit 21 in FIG. 1. 3 is a timing chart for explaining servo gate control in the embodiment. 4 is a timing chart for explaining servo gate control when a start bit is missing in the embodiment. 9 is a flowchart for explaining a servo interrupt process by the CPU 24 in the embodiment. FIG. 4 is a view for explaining calculation of servo gate timing by a calculator 226 in the embodiment. 9 is a flowchart for explaining servo control executed in a servo interrupt process by the CPU 24 in the embodiment. 9 is a flowchart for explaining a modified example of the servo control executed in the servo interrupt processing by the CPU 24 in the embodiment. 9 is a flowchart for explaining another modified example of the servo control executed in the servo interrupt processing by the CPU 24 in the embodiment.

Explanation of reference numerals

11a, 1b: disk, 12: head, 15: VCM (voice coil motor), 19: head IC, 20: R / W channel (first detecting means, servo detecting means), 21: servo processing circuit, 24: CPU (control means), 25 FROM (flash ROM), 210 start bit detector (SB detector, specific pulse output means), 211 main counter (first counter), 212 actual servo interval register, 214 ... Start bit continuous detector (second detecting means), 215 ... Start bit missing detector (SB missing detector, third detecting means), 216 ... Start bit counter (SBCNT, second counter), 221 ... Servo register.

Claims (5)

Servo information including position information, a plurality of disks having a recording surface on which servo information including a unique servo mark for identifying the servo information is recorded in advance on the same circumference at equal intervals,
A head provided corresponding to each recording surface of the plurality of disks and used for read / write for the corresponding disks;
Servo detection means for detecting the servo mark and the position information from the read information read from the disk by the head,
Interrupt generation means for generating an interrupt signal at a timing when the servo mark is detected by the servo detection means,
An interrupt process is started in response to the interrupt signal, and the position of the head calculated from the position information detected by the servo detection unit, or the current position of the head predicted from the position information detected last time by the servo detection unit. A control unit that performs servo control using one of the head positions, and determines whether to use any of the calculated head position or the predicted head position, at least between different disks. A disk storage device, comprising: control means for switching between a case where the number of times of the interrupt processing from the start of head switching is within a specified number and a case where the number of times is other than that. The control unit may be configured such that at least the number of times of the interrupt processing from the start of head switching between the different disks is within a specified number of times and the number of times of the interrupt processing from the start of head switching exceeds the specified number of times. The position of the head calculated from the position information detected by the servo detecting means is within a specified range determined by the current position of the head predicted from the position information detected last time by the servo detecting means. In the case, the servo control is executed using the calculated head position, the number of times of the interrupt processing from the start of the head switching exceeds the specified number, and the calculated head position is within the specified range. If the distance is out of the range, servo control is executed using the predicted head position. The disk drive in claim 1. The control means is configured to determine at least the number of times of the interrupt processing from the start of head switching between the different disks within a specified number of times and the position of the head calculated from position information detected by the servo detection means, The number of times of the interrupt processing from the start of the head switching is equal to or less than the specified number of times when the value falls within a first specified range determined by the current position of the head predicted from the position information detected last time by the means. If the calculated head position exceeds the first specified range determined by the predicted head position and exceeds the first specified range, the calculated head position is calculated using the calculated head position. Servo control is performed, and the number of times of the interrupt processing from the start of the head switching is within the specified number of times and the calculated The head position is out of the first specified range, and the number of times of the interrupt processing from the start of the head switching exceeds the specified number of times, and the calculated head position is in the second specified range. 2. The disk storage device according to claim 1, wherein when the value is out of the range, the servo control is performed using the predicted head position. At least a first predicted value parameter determined by a difference in position information between heads used for predicting a head position immediately after head switching between different disks, and a first predicted value parameter used for predicting a head position except immediately after head switching A non-volatile storage device in which two predicted value parameters are stored in advance;
The controller reads the first predicted value parameter from the nonvolatile storage device at least in the interrupt processing in which the number of times of the interrupt processing from the start of head switching between the different disks is within a specified number. In the interrupt processing, the second predicted value parameter is read from the non-volatile storage device, and the position of the head calculated from the position information detected by the servo detecting means is determined by the read parameter value and the servo detection value. If the head is within a specified range determined by the current position of the head predicted from the position information detected last time by the means, the servo control is performed using the calculated head position, and the calculated head position is calculated. If the head position is out of the specified range, servo control is performed using the predicted head position. Disk storage device according to claim 1, wherein the control is executed. A plurality of disks each having a recording surface on which servo information including position information, and servo information including a unique servo mark for identifying the servo information is previously recorded at equal intervals on the same circumference; And a head provided for the respective recording surfaces of the plurality of disks and used for read / write for the corresponding disks. A method for compensating for positional deviation of servo information for compensating for
Detecting the servo mark and the position information from the read information read from the disk by the head;
Generating an interrupt signal at a timing when the servo mark is detected;
An interrupt process is started in response to the interrupt signal, and the position of the head calculated from the detected position information, or the current position of the head predicted from position information detected last time prior to the position information Performing servo control using one of the positions, and determining whether to use the calculated head position or the predicted head position by using at least a head switching start between different disks. A step of switching between a case where the number of times of the interrupt processing from the time is within a specified number and a case where the number of times is other than the specified number.

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