JPH11185211A - Magnetic disk device and processing method in seek error adapted to its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reading a cylinder code and preventing a seek error even when a seek error has been caused by reduction of an output of a read-signal and the like by adding newly retry-processing in seek error resulted from varying sense current quantity. SOLUTION: When seek error has been caused without being able to decode a cylinder code normally from a read-signal reproduced by a magnetic resistance effect type (MR) head 12a in seek operation in which a head (compound separation type head) 12 is sought to a target cylinder on a disk 11, a CPU 20 repeats retry-processing with the specified number of times as the upper limit. Nevertheless, when seek error cannot be dissolved, sense current adjusting processing utilizing a function adjusting sense current quantity supplied to the MR head 12a is repeated until seek error is dissolved increasing successively sense current quantity to the upper limit of an adjustable range of sense current quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic disk drive using a magnetoresistive head for reproducing data from a disk, and a seek error processing method applied to the magnetic disk drive.

[0002]

2. Description of the Related Art In a conventional magnetic disk device (hard disk device), a MIG (Metal In Gap) head and a thin film head are mainly used as heads for recording data on a disk as a recording medium and reproducing data from the disk. Met.

However, in recent years, in order to realize a higher recording density (higher capacity) of a magnetic disk drive, a magneto-resistive head (Magnet Resistive) head, that is, a read-only (reproducing) head called an MR head has been adopted. Magnetic disk drives are increasing.

The MR head can control a reproduction output value from the head amplifier circuit by setting a sense current from the head amplifier circuit (head amplifier IC). This output value is substantially proportional to (the current amount of) the sense current, and the more the sense current flows, the larger the output value. If the output value is small, a read error may occur at the time of data reproduction. Therefore, increasing the output value by flowing a large amount of sense current is convenient when reading data. However, on the other hand, the life of the MR head is shortened when a large amount of sense current is continuously supplied. Therefore, it is important to set an optimal amount of sense current.

On the other hand, JP-A-9-81909 discloses that
In a magnetic disk device using an MR head, if a read error occurs during data reproduction, the retry process is repeated a specified number of times, and then the sense current of the MR head is changed to execute the retry process. A setting technique (hereinafter referred to as prior art) is disclosed. According to this prior art, when a normal data reproducing operation can be performed by the retry process after the change of the sense current amount,
The changed sense current is stored in the memory as an optimum value, and from the next data reproduction, the stored sense current is reset to reduce the number of unnecessary retry processes, and as a result, the retry process is performed. We are trying to improve efficiency.

[0006]

However, the above prior art is a technique for setting a sense current in a retry process when a read error occurs, and the cylinder code is reduced due to a decrease in output of a read signal (reproduction output signal) or the like. A case where a seek error has occurred due to improper reading cannot be considered. For this reason, in a normal retry process at the time of a seek error, if the cause of the seek error is a decrease in the output of the read signal or the like, there is a problem that the seek error cannot be dealt with.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has as its object to provide a magnetoresistive head even when a seek error occurs due to a failure in reading a cylinder code due to factors such as a decrease in output of a read signal. By adding a new retry process at the time of seek error by changing the amount of sense current supplied to the disk, the cylinder code can be read, and the magnetic disk device and the device capable of seeking to the target cylinder can be used. An object of the present invention is to provide a seek error processing method to be applied.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a recording / reproducing head (composite separated type head) including a read-only MR head (magnetoresistive head) based on servo data including a cylinder code recorded on a disk. ) Is provided with a sense current setting means for setting the amount of a sense current supplied to the MR head, and amplifies a read signal reproduced by the MR head. During the seek operation of reading the cylinder code from the head amplifier circuit and the read signal amplified by the head amplifier circuit and moving the recording / reproducing head to the target cylinder on the disk based on the cylinder code, the cylinder code is normally If a seek error occurs during reading, the cylinder code will be read again. A retry processing means for repeating the processing a specified number of times as an upper limit, and changing the set value of the sense current setting means in the head amplifier circuit when the seek error is not eliminated even after the specified number of retry processings are repeated. And a sense current adjustment control means for restarting the retry processing means.

As described above, according to the present invention, as a retry process when a seek error occurs because the cylinder code cannot be read normally, a retry process for a seek error by changing the amount of sense current supplied to the MR head is newly performed. Even if a seek error occurs due to factors such as a decrease in the output of the read signal or a defect, the retry process is restarted with the sense current amount adjusted to compensate for the decrease in the output of the read signal. You. For this reason, it becomes possible to read the cylinder code normally, and it is possible to eliminate the seek error and seek to the target cylinder.

The present invention also provides the above head amplifier circuit,
Built-in waveform distortion detection means for detecting vertical asymmetry in which the waveform of the read signal amplified by the head amplifier circuit is asymmetric on the positive side and the negative side, signal processing required for data reproduction from the read signal, and A read / write circuit for performing signal processing necessary for data recording of the disk, reading a cylinder code from data reproduced by the read / write circuit, and moving a recording / reproducing head to a target cylinder on a disk based on the cylinder code. If a seek error occurs during the moving seek operation and a cylinder code cannot be read normally, the retry processing means for repeating the retry processing for rereading the cylinder code up to the specified number of times and the retry processing for the specified number of times are repeated. The seek error is not eliminated, and the waveform distortion detection means detects vertical asymmetry of the waveform If it is set, the adjustment process of changing the set value of the sense current setting means in the head amplifier circuit and restarting the retry processing means is performed by alternately changing the set value up and down within the settable range of the sense current setting means. A first sense current adjustment control unit that repeats until the seek error is eliminated while sequentially changing the seek error; a seek error is not eliminated even if the retry process is repeated a specified number of times; If the detection value is not detected, the adjustment process of changing the set value of the sense current setting means in the head amplifier circuit and restarting the retry processing means is sequentially performed up to the upper limit of the settable range of the sense current setting means. A second sense current adjustment control unit that repeats the increase in seek error until the seek error is eliminated.

As described above, according to the present invention, as a retry process when a seek error occurs because a cylinder code cannot be read normally, a retry process for a seek error by changing the amount of sense current supplied to the MR head is newly performed. And applying a sense current adjustment method according to the presence or absence of waveform distortion such as vertical asymmetry of the read signal waveform. If there is waveform distortion, the sense current adjustment process is performed It repeats until the seek error is eliminated while changing the sense current amount alternately up and down within the adjustable range of the above, and when there is no waveform distortion,
By repeating the adjustment process of the sense current amount until the seek error is eliminated while sequentially increasing the upper limit of the adjustable range of the sense current amount, the seek operation can be performed due to factors such as a decrease in the output of the read signal, waveform distortion, and defects. Even if an error occurs, the retry process is restarted in a state where the sense current amount is adjusted to compensate for the decrease in the output of the read signal or the waveform distortion is reduced. For this reason, it becomes possible to read the cylinder code normally, and it is possible to eliminate the seek error and seek to the target cylinder.

The above description is not limited to the retry processing when an error (seek error) occurs in a seek operation for seeking a recording / reproducing head (composite separated type head) to a target cylinder. Can be applied to retry processing when an error (first seek error) occurs in the first seek for moving from the specific zone where is located to the data zone.

The present invention is also characterized in that the sense current is returned to an initial value when a seek error (fast seek error) can be avoided as a result of adjusting the sense current.

In this manner, the state where the amount of sense current is increased despite the fact that the seek error (first seek error) is caused by a temporary factor continues to shorten the life of the MR head. Such a problem can be prevented.

[0015]

Embodiments of the present invention will be described below 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 FIG. 1, reference numeral 11 denotes a disk (magnetic disk) which is a medium on which data is recorded, and 1
Reference numeral 2 denotes a head (magnetic head) used for writing data to the disk 11 (data recording) and reading data from the disk 11 (data reproduction). Here, it is assumed that a single disk 11 is provided, but there is also a case where a plurality of disks 11 are provided. Head 12 is MR
MR as read-only head constructed using elements
This is a recording / reproducing separation type head (composite separation type head) having a head 12a and an inductive type thin film head 12b as a recording head, and is provided corresponding to each data surface of the disk 11.

A large number of concentric tracks are formed on both surfaces of the disk 11, and each track is used for positioning control or the like (a cylinder code indicating a cylinder number, and a waveform representing a position error in the cylinder indicated by the cylinder code). A plurality of servo areas in which servo data is recorded (including burst data for indicating the amplitude of the data) are arranged at equal intervals. These servo areas are radially arranged on the disk 1 from the center over each track. A data area (user area) is provided between the servo areas, and a plurality of data sectors are set in the data area.

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

The spindle motor 13 and the voice coil motor 15 are connected to a motor driver 16. The motor driver 16 drives the motor 13 by supplying a control current to the spindle motor 13 and drives the motor 15 by supplying a control current to the voice coil motor 15. The value of the control current (operation control amount) is determined by a calculation process of the CPU (microprocessor) 20, and is given as an analog value via a D / A (digital / analog) converter (not shown).

Each head 12 is connected to a head amplifier circuit (head IC) 17 mounted on, for example, a flexible printed wiring board (FPC). The head amplifier circuit 17 controls input / output of a read / write signal to / from the head 12 and the like. The head amplifier amplifies the analog output read by the head 12 and the head amplifier circuit 17 which is sent from the read / write circuit 18. Head 12 according to incoming write data
And a write driver (both not shown) for outputting a write signal (write current). The head amplifier circuit 17 also includes a sense current source circuit for supplying a sense current to (the MR element of) the MR head 12a, and a sense current setting register (for setting the amount of sense current output from the sense current source circuit). (Both are not shown).

Read / write circuit (read / write I
C) 18 receives an analog output (read signal of the head 12) read from the disk 11 by the head 12 and amplified by the head amplifier in the head amplifier circuit 17, and performs a signal process necessary for data reproduction operation A function (read channel), an encode function (write channel) for performing signal processing required for recording data on the disk 11, and a process for extracting burst data from servo data required for servo processing such as head positioning control are performed. And a signal processing function. The read / write circuit 18 also includes an adjustment circuit for adjusting the amount of the sense current output from the sense current source circuit in the head amplifier circuit 17 according to control data (sense current amount setting data) from the CPU 20, and a head. A detection circuit (not shown) for asymmetry of the waveform of the read signal output from the amplifier circuit 17 is provided.

The servo processing circuit 19 receives the data reproduced by the read / write circuit 18 and executes signal processing necessary for servo processing. That is, the servo processing circuit 19 has a timing generation function of generating various timing signals such as servo gates that are valid only during the servo area from the data reproduced by the read / write circuit 18. It has a decoding function of extracting and decoding the cylinder code. The servo processing circuit 19 also has an A / D conversion function of A / D (analog / digital) converting burst data (analog signal) extracted by the read / write circuit 18 and outputting the converted data to the CPU 20.

The CPU 20 is, for example, a one-chip microprocessor. The CPU 20 forms a main control device that controls each unit in the magnetic disk device according to a control program stored in the ROM 21. That is, CPU
Reference numeral 20 denotes a cylinder code in the servo data extracted by the servo processing circuit 19 and a burst data in the servo data extracted by the read / write circuit 18 (the voice coil motor 1 via the motor driver 16).
Well-known control processing such as seek / positioning control for moving the head 12 to a target position (by controlling the driving of the head 5) and transfer control of read / write data by controlling the HDC 24 are performed. In addition, the CPU 20 performs a process at the time of a seek error. The process at the time of the seek error includes a process of adjusting the amount of the sense current supplied to the MR head 12a, which is related to the present embodiment.

The CPU 20 includes a ROM (Read Only Memory) 21 for storing a control program for controlling each unit in the magnetic disk device, and a RAM (Random Access Memory) for providing a work area of the CPU 20 and the like.
22 and an EEPROM (Electrically Erasable and Programmable) as a rewritable nonvolatile memory used for storing parameters for controlling the magnetic disk drive.
capable Read Only Memory) 23 is connected.

The CPU 20 is also connected to an HDC (disk controller) 24. The HDC 24 controls communication of commands and data with a host device (not shown), and controls data communication with the read / write circuit 18 (via the disk 11). The HDC 24 is connected to a buffer memory (buffer RAM) 25 that stores read / write data in a cache system, for example, a RAM or the like, and a host interface 26. Host interface 26
Interfaces between the HDC 24 and the host device. The HDC 24 communicates commands and data with the host device via the host interface 26.

Next, seek processing and seek error processing in the magnetic disk drive having the configuration shown in FIG. 1 will be described with reference to flowcharts shown in FIGS. It is assumed that the CPU 20 has started a seek process (seek operation) for moving the head 12 to a target cylinder on the disk 11 in order to execute a disk read / write specified by the host device.

In this state, the data (servo data) of the servo area recorded on the disk 11 is read by the MR head 12a, and the read output (read signal) is amplified by the head amplifier circuit 17 and read / write circuit 18 Supplied to

The read / write circuit 18 reproduces data from the read signal amplified by the head amplifier circuit 17. The servo processing circuit 19 receives the data reproduced by the read / write circuit 18, and extracts and decodes a cylinder code in the servo data recorded in the servo area. Then, if the cylinder code can be decoded normally (read normally), if the decoded cylinder code cannot be decoded normally, a read error (seek Error) to the CPU 20.

If the cylinder code can be read normally in the cylinder code reading operation (steps S1 and S2), the CPU 20 compares the cylinder code with the target cylinder and moves the head 12 to the target cylinder position. It is checked whether or not it has been performed (step S3).

If the head 12 has not reached the target cylinder position, the CPU 20 calculates an operation control amount corresponding to the difference between the current cylinder position of the head 12 indicated by the read cylinder code and the target cylinder position, The control amount is supplied to a motor driver 16 through a D / A converter to drive the voice coil motor 15 so that the head 1
2 is moved (step S4). And CPU 20
Returns to step S1, and performs the operation of reading the next cylinder code using the servo processing circuit 19.

If the cylinder code cannot be read normally in this cylinder code reading operation (step S2), the CPU 20 determines that a seek error has occurred and performs an error process (a process at a seek error) (step S2).
5). The CPU 20 performs this seek error process in FIG.
Is executed as follows in the procedure shown in the flowchart of FIG.

First, the CPU 20 performs a retry process for reading the cylinder code again (step S11). If the retry process is successful, that is, if the cylinder code is normally read by reading the cylinder code again (step S12), the process exits the seek error process and proceeds to step S3 in the flowchart of FIG.

On the other hand, if the retry process fails,
The CPU 20 sets the specified number of times as an upper limit (step S1).
3) Until the retry process succeeds (step S1)
2), repeat the retry process of step S11.

If the cylinder code cannot be read normally even after the specified number of retries, the CPU
20 performs a characteristic process described below. First, CPU2
0 is a read / write circuit (read / write IC) 18
Utilizing the function of detecting the vertical asymmetry of the waveform of the read signal provided by the head amplifier circuit 17
Whether the amplitude of the waveform of the read signal by the R head 12a is asymmetric (vertical asymmetry) beyond a certain reference value on the positive side and the negative side (in other words, the cylinder code is normal because the vertical asymmetry of the waveform is large) It is checked whether a read error has occurred and a seek error has occurred) (step S14).

If the waveform of the read signal is vertically asymmetric, that is, if there is a waveform distortion, the CPU
Reference numeral 20 denotes the value of the sense current setting register in the head amplifier circuit (head IC) 17, for example, +1 TAP (tap)
After changing the reproduction output from the MR head 12a by adjusting (the amount of current) the sense current supplied from the sense current source circuit in the head amplifier circuit 17 to the MR head 12a (step S16). The retry process with the specified number of times as the upper limit is repeated (steps S11 to S11).
13). If the retry still fails,
U20 sets the value of the sense current setting register to -1T this time.
By adjusting the sense current by changing the AP (step S16), the reproduction output from the MR head 12a is reduced, and then the retry process is repeated up to a specified number of times (steps S11 to S13). If the retry still fails, the CPU 20 adjusts the sense current by changing the value of the sense current setting register by +2 TAP this time (step S16) to further increase the reproduction output from the MR head 12a. The retry process with the specified number of times as the upper limit is repeated (steps S11 to S13).

That is, the CPU 20 changes the value of the sense current setting register to +1 TAP → − until the retry succeeds.
1TAP → + 2TAP → -2TAP → + 3TAP → -3
The amplitude of the reproduction output from the MR head 12a is changed by changing the TAP number alternately between positive and negative and sequentially increasing the absolute value as in TAP → (step S16). Repeat the retry while doing.

If the retry succeeds in the sense current adjustment within the settable range (sense current adjustable range) of the sense current setting register, the CPU 20 exits the seek error processing and returns to the step in the flowchart of FIG. Proceed to S3. On the other hand, if the retry is not successful even after adjustment to the boundary of the settable range of the sense current setting register (step S15), the CPU 20 returns an error to the host device and ends the error.

On the other hand, when the waveform of the read signal is not vertically asymmetric, there is another cause of a seek error (a cause that the cylinder code could not be read normally even after executing the retry process a specified number of times) ( If the reproduction output of the MR head 12a is small, if the cylinder code portion on the disk 11 has a defect, or the like (step S14), C
The PU 20 changes the value of the sense current setting register in the head amplifier circuit (head IC) 17 by, for example, +1 TAP, and changes the value from the sense current source circuit in the head amplifier circuit 17 to M
By adjusting (the amount of current) the sense current supplied to the R head 12a (step S18), the MR head 12a
After increasing the reproduction output from, the retry process with the specified number of times as the upper limit is repeated (steps S11 to S13).
If the retry still fails, the CPU 20
Sets the value of the sense current setting register to +21 TAP
The sense current is adjusted by changing (step S1).
8) After the reproduction output from the MR head 12a is further increased, the retry process is repeated up to a specified number of times (steps S11 to S13).

That is, the CPU 20 changes the value of the sense current setting register to +1 TAP → +
By increasing the sense current by 1 TAP at a time to the upper limit of the settable range of the sense current setting register, as in 2TAP → + 3TAP →... (Steps S17, S1)
8) Retry is repeated while gradually increasing the amplitude of the reproduction output from the MR head 12a.

If the retry succeeds in adjusting the sense current within the settable range of the sense current setting register, the CPU 20 exits the seek error processing and proceeds to step S3 in the flowchart of FIG. On the other hand, if the retry is not successful even after adjusting the upper limit of the settable range of the sense current setting register (step S1).
7), the CPU 20 returns an error to the host device and terminates with an error.

As described above, the retry is performed by adjusting (the amount of) the sense current supplied to the MR head 12a, whereby the output of the reproduction output from the MR head 12a is reduced, the waveform is distorted, and the cylinder code portion is slightly damaged. Therefore, even if a seek error occurs due to the above, the seek error can be eliminated, and the reliability of the apparatus can be improved.

The inventor has come to recognize that the cause of the seek error may be temporary. For this reason, it is useless to fix the value of the sense current supplied to the MR head 12a to the value adjusted in step S16 or S18 in view of the life of the MR head 12a.

Therefore, in the present embodiment, as shown in the flowchart of FIG. 2, when the head 12 can be sought to the target cylinder (step S3), if the sense current amount has been adjusted (step S6), Head amplifier circuit 1
7, the value of the sense current setting register is returned to the initial value (step S7).

In the above embodiment, the disk 11
Although the seek processing for moving the head 12 to the upper target cylinder has been described, the present invention can be similarly applied to the first seek.

The first seek means that no servo data is recorded on the disk 11 when the magnetic disk device is in a non-operation state (rotation state of the disk).
The head 12 located in a specific zone, which is a non-data zone generally called a CSS (Contact Start Stop) zone, escapes from the specific zone when the apparatus is started up and moves to the data zone (servo data is recorded). It means to let.

In the first seek, the cylinder code is read from the servo data recorded in the data zone only after the head 12 escapes from the specific zone to the data zone. Therefore, if the cylinder code cannot be read for some reason, it is not known whether the head 12 is still in the specific zone or has escaped to the data zone. Therefore, as a simple method, it is assumed that the head 12 is on the data zone after a certain period of time has elapsed, and that if a cylinder code cannot be read in that state, a first seek error has occurred. .

[0047]

As described above in detail, according to the present invention, as a retry process when a seek error occurs because a cylinder code cannot be read normally, a seek operation by changing the amount of sense current supplied to the MR head is performed. By adding the retry processing at the time of error, even if a seek error occurs due to factors such as a decrease in the output of the read signal or a defect, the cylinder code can be read normally.
The seek cylinder can be sought by eliminating the seek error.

Further, according to the present invention, as a retry process when a seek error occurs because a cylinder code cannot be read normally, a retry process for a seek error by changing the amount of sense current supplied to the MR head is newly performed. Add
Moreover, the sense current adjustment method is applied in accordance with the presence or absence of waveform distortion such as vertical asymmetry of the read signal waveform, and the adjustment processing of the sense current amount is performed. Iteratively changing the sense current amount up and down repeatedly until the seek error is eliminated.If there is no waveform distortion, the sense current amount is sequentially increased to the upper limit of the adjustable range of the sense current amount. By repeating until the seek error is eliminated while increasing, even if the read signal output drops, waveform distortion,
Even if a seek error occurs due to a defect or the like, the sense current is adjusted to compensate for the decrease in the output of the read signal, or the retry process is restarted with the waveform distortion reduced, so the cylinder code is normal. Thus, the seek cylinder can be sought and the seek cylinder can be sought.

According to the present invention, when a seek error can be avoided as a result of adjusting the amount of sense current, the amount of sense current is returned to an initial value. It is possible to prevent a problem that the state in which the amount of sense current is increased despite the occurrence of the phenomenon and the life of the MR head is shortened.

[Brief description of the drawings]

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

FIG. 2 is a flowchart for explaining a seek process in the embodiment.

FIG. 3 is a flowchart for explaining a process at the time of a seek error in step S5 in FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Disk 12 ... Head (recording / reproducing head) 12a ... MR head (magnetoresistance effect type) 17 ... Head amplifier circuit (sense current setting means) 18 ... Read / write circuit (waveform distortion detection means) 19 ... Servo processing circuit 20 ... CPU (retry processing means, sense current adjustment control means, first sense current adjustment control means, second sense current adjustment control means)

Claims (8)

[Claims] 1. A magnetic disk drive for seeking and positioning a recording / reproducing head including a read-only magnetoresistive head to a designated position on a disk based on servo data including a cylinder code recorded on the disk. A head amplifier circuit incorporating sense current setting means for setting a current amount of a sense current supplied to the magnetoresistive head, and amplifying a read signal reproduced by the magnetoresistive head; During a seek operation for reading the cylinder code from the amplified read signal and moving the recording / reproducing head to a target cylinder on the disk based on the cylinder code, the cylinder code cannot be read normally and a seek error occurs. If it occurs, retry processing to re-read the cylinder code Retry processing means for repeating a fixed number of times as an upper limit, and if the seek error is not eliminated even after repeating the specified number of times of retry processing, the set value of the sense current setting means in the head amplifier circuit is changed and A magnetic disk drive comprising: a sense current adjustment control unit for restarting a retry processing unit. 2. A magnetic disk drive for performing seek / position control of a recording / reproducing head including a read-only magnetoresistive head to a specified position on a disk based on servo data including a cylinder code recorded on the disk. A head amplifier circuit incorporating sense current setting means for setting a current amount of a sense current supplied to the magnetoresistive head, and amplifying a read signal reproduced by the magnetoresistive head; Built-in waveform distortion detection means for detecting vertical asymmetry in which the amplified read signal waveform is asymmetric on the positive side and the negative side, and performs signal processing necessary for data reproduction from the read signal and data recording on the disk. A read / write circuit for performing necessary signal processing; and the data read by the read / write circuit. During a seek operation of reading a Linder code and moving the recording / reproducing head to a target cylinder on the disk based on the cylinder code, if a seek error occurs without reading the cylinder code normally, the cylinder code Retry processing means for repeating a retry process of re-reading a specified number of times as an upper limit, seek error is not eliminated even if the specified number of retry processes are repeated, and the waveform distortion detecting means detects vertical asymmetry of the waveform. If it is determined that the setting value of the sense current setting means in the head amplifier circuit is changed and the retry processing means is restarted, the adjustment processing is performed within the settable range of the sense current setting means. First sense current adjustment that is repeated alternately up and down until the seek error is eliminated Control means, if the seek error is not eliminated even if the retry process is repeated the specified number of times, and if the waveform distortion detecting means does not detect the vertical asymmetry of the waveform, the sense current in the head amplifier circuit Adjustment processing for changing the set value of the setting means and restarting the retry processing means,
A magnetic disk drive comprising: a second sense current adjustment control unit that repeats until the seek error is eliminated while sequentially increasing the set value up to the upper limit of the settable range of the sense current setting unit. 3. The apparatus according to claim 2, further comprising an initialization unit for returning the set value of said sense current setting unit to an initial value when said seek error is eliminated and said recording / reproducing head can be moved to a target cylinder. Claim 1 or Claim 2
The magnetic disk device according to the above. 4. A data zone in which servo data including a cylinder code is recorded and a specific zone for keeping a recording / reproducing head including a read-only magnetoresistive head in a non-operating state are secured. A disk, and seek / read the recording / reproducing head to a designated position on the disk based on servo data recorded on the disk;
In a magnetic disk drive for performing positioning control, a head amplifier incorporating sense current setting means for setting a current amount of a sense current supplied to the magnetoresistive head, and amplifying a read signal reproduced by the magnetoresistive head A first seek means for causing the recording / reproducing head to escape from the specific zone and move to the data zone when the apparatus is started; and When the first seek error occurs because the cylinder code cannot be read normally from the read signal amplified by the head amplifier circuit in a state where the head has escaped, a retry process of rereading the cylinder code is performed up to a specified number of times. Retry processing means to be repeated, and the specified number of times If the first seek error is not resolved even after repeating the retry processing, the sense current adjustment control means for changing the set value of the sense current setting means in the head amplifier circuit and restarting the retry processing means; A magnetic disk drive comprising: 5. A data zone in which servo data including a cylinder code is recorded, and a specific zone for keeping a recording / reproducing head including a read-only magnetoresistive head in a non-operating state. A disk, and seek / read the recording / reproducing head to a designated position on the disk based on servo data recorded on the disk;
In a magnetic disk drive for performing positioning control, a head amplifier incorporating sense current setting means for setting a current amount of a sense current supplied to the magnetoresistive head, and amplifying a read signal reproduced by the magnetoresistive head Circuit, and a built-in waveform distortion detecting means for detecting vertical asymmetry in which the waveform of the read signal amplified by the head amplifier circuit is asymmetric on the positive side and the negative side, and performing signal processing necessary for data reproduction from the read signal. A read / write circuit for performing signal processing necessary for data recording on the disk; and performing a first seek for moving the recording / reproducing head out of the specific zone and moving to the data zone when the apparatus is started. First seek means; and the recording / reproducing head escapes to the data zone in the first seek. If a first seek error occurs because the cylinder code cannot be read normally from the data reproduced by the read / write circuit in this state, a retry process for rereading the cylinder code is repeated up to a specified number of times. Processing means, if the first seek error is not eliminated even if the retry processing of the specified number of times is repeated, and the waveform distortion detecting means detects vertical asymmetry of the waveform,
The adjustment process of changing the set value of the sense current setting unit in the head amplifier circuit and restarting the retry processing unit is performed by sequentially changing the set value up and down within a settable range of the sense current setting unit. A first sense current adjustment control unit that repeats until the first seek error is eliminated, and a first seek error is not eliminated even if the retry process is repeated the specified number of times, and the waveform distortion detection unit repeats the first seek error. When the vertical asymmetry is not detected, the adjustment process of changing the set value of the sense current setting unit in the head amplifier circuit and restarting the retry processing unit is performed by adjusting the setting range of the sense current setting unit. A second sense current adjustment that is repeated until the first seek error is eliminated while sequentially increasing the set value to the upper limit. A magnetic disk drive comprising a control unit. 6. An initialization means for returning a set value of said sense current setting means to an initial value when said first seek has been canceled and said recording / reproducing head can be moved to a target cylinder. The magnetic disk drive according to claim 4 or 5, wherein: 7. A magnetic disk drive that seeks and positions a read / write head including a read-only magnetoresistive head at a specified position on a disk based on servo data including a cylinder code recorded on the disk. A read error signal read by the magnetoresistive head, and reads and writes the recording / reproducing head to a target cylinder on the disk based on the cylinder code. When a seek error occurs because the cylinder code cannot be read normally during the moving seek operation, a step of repeating a retry process of rereading the cylinder code up to a specified number of times, and repeating the retry process of the specified number of times. However, if the seek error has not been resolved, Seek error when processing method characterized by by changing the sense current supplied to the de and a step of restarting the retry processing. 8. A function for performing seek / positioning control of a recording / reproducing head including a read-only magnetoresistive head to a designated position on a disk based on servo data including a cylinder code recorded on the disk; A seek error processing method applied to a magnetic disk drive having a function of detecting a vertical asymmetry in which a waveform of a read signal reproduced by a resistance effect type head is asymmetrical on a positive side and a negative side, wherein the magnetoresistive effect type During a seek operation of reading the cylinder code from a read signal reproduced by a head and moving the recording / reproducing head to a target cylinder on the disk based on the cylinder code, the cylinder code cannot be read normally and a seek operation is performed. When an error occurs, the retry process for re-reading the cylinder code is limited to the specified number of times. Repeating, and determining whether or not vertical asymmetry of the waveform of the read signal has been detected if the seek error has not been resolved even after repeating the retry process the specified number of times. In this case, the adjustment process for changing the amount of sense current supplied to the magnetoresistive head and restarting the retry process is performed alternately with the amount of current up and down within the adjustable range of the amount of sense current. And repeating the above until the seek error is eliminated, and when no vertical asymmetry is detected, changing the amount of sense current supplied to the magnetoresistive head and restarting the retry process Until the seek error is eliminated while sequentially increasing the current amount up to the upper limit of the adjustable range of the sense current amount. And a repetition step.