JP3349392B2 - Storage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage device for recording information demodulated by partial response maximum likelihood detection (PRML) on a medium, and more particularly, to a write pre-compensation amount for compensating for a peak shift at the time of reading. And a storage device, such as a magnetic disk device, which automatically adjusts settings according to the conditions.

[0002]

2. Description of the Related Art In recent years, the capacity of magnetic disk drives has been increasing, and the bit density has been decreasing as the capacity has increased. In a conventional magnetic disk device, a write / read method using a partial response maximum likelihood detection method (hereinafter, referred to as a “PRML” method) which is strong in a high bit density is becoming mainstream, with a magnetization reversal interval becoming shorter with an increase in capacity. I have.

[0003] A PRML having an increased magnetic recording density as described above.
In a magnetic disk device that performs read / write of the system, FIG.
When the long magnetization reversal interval 100 and the short magnetization reversal interval 101 continue as in FIG.
11 (B) corresponding to the write current switching point (magnetization direction transition point) 103 which gives the boundary of the next magnetization reversal interval 102 due to insufficient magnetic recording. On the other hand, FIG.
Non-linear bit shift (NLTS) 1 which shifts like the read peak waveform 105 of FIG.
06 occurs.

[0004] This non-linear bit shift can be said to be a write effect usually caused by a magnetostatic interaction that occurs between closely spaced magnetic transitions. When such a non-linear bit shift occurs in the read waveform reproduced by the PRML method, the position of the sample point when the waveform equalization based on the partial response is performed is shifted, and the prediction by the maximum likelihood detection is deviated. cause.

Therefore, in the conventional apparatus, FIG.
12C, the shift amount of the non-linear bit shift 106 is measured in advance, and the write current switching point 103 before compensation in FIG. 12A is delayed by the non-linear bit shift 106 shift amount. Write pre-competition (writing pre-compensation). The read waveform of the magnetic recording that has been subjected to the compensation writing by the write pre-competition in FIG. 12B is as shown in FIG. 12C, and the reproduced waveform 108 of the delayed switching point 107 is shifted by being subjected to the non-linear bit shift. Then, a read waveform obtained at a position corresponding to the switching point before compensation in FIG. 12A and having a bit interval is reproduced,
Non-linear bit shift can be canceled.

[0006]

SUMMARY OF THE INVENTION However, PRM
The non-linear bit shift of the read waveform, which is a problem in the L-type reproduction process, is greatly affected by the temperature of the magnetic disk medium. This is because the hysteresis curve in the BH characteristic (magnetization characteristic) of the disk medium changes as shown in FIG.

That is, the BH curve of the magnetic disk medium is
It has hysteresis characteristics like the solid line at room temperature,
As the temperature decreases, the hysteresis increases as indicated by the broken line.
Here, the recording magnetic field H is proportional to the write current flowing through the write head, Br is the residual magnetic flux density, and Hc is the coercive force. The non-linear bit shift is also affected by a change in the flying height of the head depending on the temperature.

In order to cope with such a temperature-dependent hysteresis characteristic of the medium and a non-linear bit shift due to a change in the flying height of the head, an environmental temperature is measured by a temperature sensor and a specified magnetic recording density (residual magnetic flux density) is measured. It is conceivable to change the write current so as to obtain. For example, when the temperature is low, the hysteresis of the medium increases as shown by the broken line in FIG. 13, so if the write current is increased so that the write magnetic field H2 is changed from the write current of the write magnetic field H1 until then,
It is possible to maintain a constant magnetic recording density (residual magnetic flux density), and eliminate a state where magnetic recording which is a cause of the nonlinear bit shift is insufficient and cannot be completely written.

However, when the write current is increased, the writing spread of the magnetized area on the medium by the write head becomes large, causing a problem that data on an adjacent track is erased. To change the write current, a switch circuit for changing the current or a dedicated D / A converter is required, and there is a problem that the amount of circuits increases.

The present invention has been made in view of such problems, and focuses on the fact that the amount of non-linear bit shift varies depending on the medium temperature, and focuses on non-linear bit shift (peak shift) during reading. On the other hand, there is provided a recording apparatus in which the influence of non-linear bit shift is canceled and the error rate is improved by changing the write pre-compensation amount for shifting the switching point of the write current in the reverse direction according to the environmental temperature. The purpose is to:

[0011]

FIG. 1 is a diagram illustrating the principle of the present invention. First, the present invention is directed to a storage device such as a magnetic disk device that writes information for demodulation by partial response maximum likelihood detection (PRML) on a medium. FIG. 18A shows such a storage device according to the present invention.
The timing of the switching point of the write current (the transition point of the magnetization direction) which gives the boundary between the long magnetization reversal interval and the next magnetization reversal interval following the short magnetization reversal region is previously delayed by a predetermined write pre-competition amount. By doing so, the write pre-competition circuit 1 for compensating the peak position of the read signal shifted at the time of reading to the correct position, and the write pre-competition circuit 1 according to the environmental temperature T detected by the temperature sensor 3 -It is characterized in that a setting processing unit 2 for setting the pre-competition amount WP to an optimum value is provided.

The setting processing unit 2 has a table 4 in which the optimum value of the write pre-competition amount corresponding to the environmental temperature is stored in advance, and refers to the table 4 based on the environmental temperature detected by the temperature sensor 3 to determine the write pre-competition amount. The optimum value is read out and set in the write pre-competition circuit 1. Further, the setting processing unit 2 writes the data on the medium when the environmental temperature changes.
It is also possible to write the test data while changing the pre-competition amount, read it out, measure the error rate, measure the error rate, find the write pre-competition amount that gives the best error rate, and set it in the write pre-competition circuit 1. Further, the temperature sensor is installed on a disk enclosure or a printed circuit board.

According to the storage device of the present invention, even if the hysteresis characteristic of the medium changes due to the temperature and the nonlinear bit shift at the time of reading deteriorates, the environmental temperature is monitored using the temperature sensor, and the environmental temperature is monitored. By changing the write pre-competition amount in accordance with the above, it is possible to avoid an adverse effect on an adjacent track due to an increase in write current or the like, and to avoid a read error due to a temperature change peculiar to the PRML method without increasing the circuit amount. it can.

[0014]

FIG. 2 shows an embodiment of a storage device according to the present invention, taking a magnetic disk device known as a hard disk drive (HDD) as an example. This magnetic disk device includes a disk enclosure 10 and a control circuit board 11. The disk enclosure 10 has an R / W mounted as a head IC circuit.
A preamplifier circuit 12, a head assembly 14, a voice coil motor (hereinafter referred to as "VCM") 15, a spindle motor 16, and a temperature sensor 3 for detecting an environmental temperature in the apparatus are provided.

The R / W preamplifier circuit 12 is multifunctional so that head selection, write current setting, MR head sense current setting, and the like can be performed by register setting by serial data transfer from the control circuit board 11 side. The head assembly 14 is provided with a plurality of composite heads each of which integrates a write head using an inductive head and a read head using an MR head, for example, in a number corresponding to the block surface of the magnetic disk medium. Of course, the head assembly 16 is supported at the tip of a head actuator driven by the VCM 15, and is moved in a direction crossing the track of the magnetic disk medium.

The control circuit board 11 has an MCU
(Micro control unit) 18, read channel circuit (RDC) 20, oscillator 22, hard disk controller (HDC) 24, flash PEROM
26, a data buffer 28 using a DROM, a servo controller 30, and an interface connector 36 with a higher-level device are provided.

When the MCU 18 receives a write access from, for example, a host device, the MCU 18 transfers the NRZ write data received through the interface connector 36 to the data buffer 28.
Then, the hard disk controller 24 outputs a write gate signal WG to the read channel circuit 20 to put it in a write operation state, and after performing a predetermined write format on the NRZ write data read from the data buffer 28, 20.

The read channel circuit 20 responds to the NRZ write data from the hard disk controller 24 by, for example, the PR4ML system (partial response class 4).
In order to perform the maximum likelihood detection method, the R / W preamplifier of the disk enclosure 10 after performing an 8/9 conversion precode and a precompetition (write precompensation) for canceling the nonlinear bit shift targeted by the present invention. Circuit 12
To a write current by a write driver,
At this time, writing is performed on the magnetic disk medium by the write head in the currently selected head assembly 10.

On the other hand, when the MCU 18 receives a read access from the host device, it activates the hard disk controller 24 and outputs a read gate signal RG to the read channel circuit 20 to perform a read operation. In this state, the read signal from the selected MR head in the head assembly 14 of the disk enclosure 10 is R
After being amplified by the preamplifier in the / W preamplifier circuit 12, the signal is supplied to the read channel circuit 20.

The read channel circuit 20 demodulates the read data by executing a Viterbi algorithm for maximum likelihood detection after performing waveform equalization on the input read signal for generating, for example, an ideal PR4 waveform, and finally executing 8/9
After performing inverse conversion to convert to NRZ data, the data is output to the hard disk controller 24. After performing ECC processing on the read data from the read channel circuit 20, the hard disk controller 24 transfers the read data to the higher-level device via the data buffer 28.

At the time of write access and read access by the MCU 18, the servo controller 30 seeks the head assembly 14 to the cylinder address determined by the access address so as to perform on-track operation.
The CM 15 is driven to perform head positioning control. FIG. 3 is a block diagram of the read channel circuit 20 provided on the control circuit board 11 of FIG. In the read channel circuit 20, first, the write modulation unit is an 8/9 encoder 42 provided following the parallel interface 40,
Precoder 44, write / pre-competition circuit 1, write F
F48. The control at the time of read / write in the read channel circuit 20 is performed by setting signals for the ports P5 to P8 of the read channel control logic 50.

That is, register setting data by serial transfer for setting the operation state of the read channel circuit 20 is supplied from the MCU 18 to the port P5. Port P
6, P7 and P8 have a hard disk controller 24
The read gate signal RG, the write gate signal WG, and the servo gate signal SG are supplied. Further, the read channel control logic 50 determines the number of delay clocks for canceling the non-linear bit shift with respect to the write pre-competition circuit 1 by register setting by serial transfer from the port P5 while the write gate signal WG is supplied to the port P7. The write / pre-competition amount WP given by is set.

The write operation by the write modulator is as follows. From port P1 to parallel interface 40
Is converted into an 8/9 code by the 8/9 encoder 42, and the PR4
After precoding 1+ (1 + D) ^m for ML,
The write pre-compensation circuit 1 delays by setting the write pre-competition amount for canceling the non-linear bit shift, and after dividing the frequency by the write FF 48, the port
4 to the disk enclosure 10 side, and magnetically writes and records on the magnetic disk medium by the write head.

The read demodulation unit of the read channel circuit 20
It is divided into a servo demodulator and a data demodulator. A read signal from the disk enclosure 10 is input to a port P9, amplified by an AGC amplifier 52, and then input to a programmable filter 54. Programmable filter 5
4 implements a function as a low-pass filter and a function as a differentiator circuit for the read signal from the AGC amplifier 52. The signal passed through the low-pass filter is applied to port P11
At the same time, it is supplied to the full-wave rectifier circuit 56 and the adaptive equalizer 60 on the data demodulation unit side.

The differentiated signal from the port P 10 by the differentiating function of the programmable filter 54 is given to a servo pulse detector 68. The servo pulse detector 68 is
The peak of the low-pass filter output signal from the port P11 is detected at the zero-cross timing of the differential signal from the port P10, and the cylinder information included in the servo information is detected and output from the port P13.

The read signal from the port P11, which is the output of the low-pass filter of the programmable filter 54, is rectified by the full-wave rectifier circuit 56 to extract the amplitude component, and is input to the servo demodulator circuit 70. A two-phase servo pattern is recorded in the servo area of the magnetic disk medium. As a result, the servo demodulation circuit 70 outputs position signals A,
B, C, and D are output from the port P12.

On the other hand, the data demodulation unit comprises an adaptive equalizer 60 for inputting a low-pass filter output signal from the port P11 of the programmable filter 54, maximum likelihood detectors 62 and 8
/ 9 decoder 64. That is, the read signal input from the disk enclosure to the port P9 is AGC
After being amplified by the automatic gain control in the amplifier 52, the signal is input to the adaptive equalizer 60 through the low-pass filter of the programmable filter 54, and after the waveform equalization conforming to PR4 is performed, the maximum likelihood detector 62 Demodulates the read data by the maximum likelihood detection according to the Viterbi algorithm.

Subsequently, after the read data detected by the 8/9 decoder 64 with the maximum likelihood is converted into the original NRZ data by performing the 8/9 inverse conversion, the port P1 is transmitted from the parallel interface 40 to the port P1.
To the hard disk controller 24 shown in FIG. Also, during the data demodulation operation, the adaptive equalizer 6
The read signal from P0 functions as a data separation circuit.
It is input to the LL circuit 66 and generates a read clock synchronized with a read signal from the disk medium. The read clock is read from the port P2 via the adaptive equalizer 60, the 8/9 decoder 64, and the parallel interface 40. The clock RCLK is output.

FIG. 4 is a functional block diagram of a write / pre-competition process according to the environmental temperature for canceling a non-linear bit shift occurring in a read signal in the magnetic disk drive of the present invention. In FIG. 4, a setting processing unit 2, a temperature sensor 3, and a table 4 are provided for the write pre-competition circuit 1. The functions of the setting processor 2 and the table 4 are realized by the MCU 18 provided on the control circuit board 11 shown in FIG. 2 and the read channel control logic 50 provided in the read channel circuit 20 shown in FIG.

The write pre-compensation circuit 1 has a write current switching point (magnetization direction transition point) which gives a boundary between a long magnetization reversal interval and a short magnetization reversal interval as shown in FIG. The timing is then set by the setting processing unit 2
Is delayed by the pre-competition amount WP set by
In writing by the delay of the switching point (magnetization direction transition point) of the write current, the non-linear bit shift generated at the time of reading is compensated so as to be at the position of the correct bit interval.

The detection signal of the environmental temperature T from the temperature sensor 3 provided in the disk enclosure 10 as shown in FIG. Setting processing unit 2
Determines whether the environmental temperature T detected by the temperature sensor 3 has exceeded a predetermined temperature slice value. If the environmental temperature T has exceeded the temperature slice value, the table 4 is referred to and the write / pre-competition amount corresponding to the changed slice value is determined. WP is read and the set value for the write / pre-competition circuit 1 is changed.

FIG. 5 shows the result of measuring the error rate with respect to the write pre-competition amount WP in the magnetic disk device of the present invention, using low, normal, and high environmental temperatures as parameters. For example, at room temperature T2,
Increasing the pre-competition amount WP also improves the error rate. After the peak value, the error rate deteriorates when the write pre-competition amount WP is further increased.

The relationship of the error rate with respect to the magnitude relationship of the write pre-competition amount WP is that when the environmental temperature is low temperature T1, it is necessary to increase the write pre-competition amount WP with respect to the normal temperature T2. Sometimes it is necessary to reduce the write pre-competition amount WP with respect to the normal temperature T2. Thus, the error rate of the write pre-competition WP differs depending on the environmental temperature.

Therefore, based on the relationship shown in FIG. 5, in the present invention, the write pre-competition amount WP with respect to the environmental temperature T as shown in FIG. 6 is set. That is, in FIG. 5, the low temperature is T1, the normal temperature is T2, the high temperature is T3, and the write / pre-competition amount WP when the error rate is the best is W, respectively.
Assuming that P1, WP2, and WP3, the characteristic of the write pre-competition amount WP with respect to the temperature T indicated by the straight line in FIG. 6 is obtained.

Therefore, in the table 4 of FIG.
Based on the above characteristic, for example, as shown in FIG. 7, the slice pre-compression amount is stored in advance with the slice temperature value as a reference address. In this table contents,
The slice temperature value is divided into n regions T1, T2, T3,... Tn, and the median value of the region determined by the slice temperature value of each region is the write pre-competition amount WP0, WP1, WP.
2,... WPn are registered in advance.

FIG. 8 is a flowchart of the write pre-competition process according to the embodiment of FIG. First, step S1
The environment temperature T detected by the temperature sensor 3 installed in the disk enclosure 10 is monitored every predetermined time cycle. In step S2, the monitored environment temperature T refers to the table 4 in FIG. Then, it is checked whether or not the temperature slice value in the table corresponding to the currently set write pre-competition amount has been exceeded.

If the detected environmental temperature T exceeds the temperature slice value of the pre-compensation amount currently set in the table, the process proceeds to step S4, and the write / pre-competition amount of the temperature slice value to which the detected environmental temperature T belongs is stored in the table. 4 to change the set amount for the write / pre-competition circuit 1. The processing of steps S1 to S4 is
This is repeated until there is a device stop instruction in step S5.

FIG. 9 shows another embodiment of the write pre-compensation processing of the present invention for canceling the non-linear bit shift. When the ambient temperature exceeds a predetermined slice value, the write pre-competition amount is changed on the magnetic disk medium. While writing and reading test data, the amount of write / pre-competition at which the error rate is the best is actually measured and the setting is changed.

In FIG. 9, the setting processing section 2 includes a test write / read instructing section 5, an error rate measuring section 6, and an optimum value setting section 7. The detection signal of the environmental temperature T from the temperature sensor 3 provided on the disk enclosure 10 side is given to the test write / read instruction unit 5. The test write / read instructing unit 5 sets a temperature range based on a slice temperature value, for example, as shown in Table 4 of FIG. 7, and when the current environmental temperature changes to another slice temperature range, the test write is performed. Perform a read instruction.

This test write / read instruction is issued at the timing of a standby state in which access from the host device is not performed. If a command from the host device is received during the write / pre-compensation amount measurement by the test write / read instructing unit 5, the measurement process is interrupted, the access from the host device is executed, and the process returns to the write / pre-competition amount measurement process again. .

The test data is written by the test write / read instructing unit 5 by repeatedly writing test data having a long magnetization reversal interval and a short magnetization reversal interval as shown in FIG. Reading is performed after writing the value while changing it by a predetermined amount ΔWP from a predetermined minimum value (WPmin) to a maximum value (WPmax) at a time.

The error rate measuring unit 6 measures the error rate of the read data of the test data written while changing the write / pre-competition amount. Optimal value setting section 7
Calculates the optimal value of the write pre-competition amount WP at which the error rate becomes the best from the measurement result of the error rate measuring unit 6, sets the optimal value in the write pre-competition circuit 1, and changes the value up to that.

FIG. 10 shows the write / write mode in the embodiment of FIG.
It is a flowchart of a pre-competition process. First, in step S1, the environmental temperature T monitored by the temperature sensor 3 provided in the disk enclosure 10 is monitored every predetermined time cycle. If the monitored environmental temperature T exceeds the predetermined slice value in step S2, the process proceeds to step S3. The head is positioned at a predetermined measurement sector determined in advance.

As the measurement sector, it is desirable to use a cylinder in the outermost or innermost system area of the magnetic disk medium. In addition, it goes without saying that a specific cylinder in the user area may be used.
Next, in step S4, the write pre-competition amount WP is set to an initial value WP1 such as a predetermined minimum value, and in step S5, after writing to a measurement sector, reading is performed to measure an error rate.

In step S6, it is checked whether the set value of the write pre-competition amount is the final set value. If not, the write pre-competition amount is set to Δ in step S7.
After updating by WP, the measurement of the error rate by writing and reading to the measurement sector in steps S4 and S5 is repeated. If it is determined in step S6 that the processing has ended based on the final set value of the write pre-competition amount, step S8 is performed.
Then, the best write pre-competition amount among the measured error rates is set as the optimum value, and the value of the write pre-competition circuit is changed to this optimum value. Such processing of steps S1 to S8 is repeated until there is a device stop instruction in step S9. The change processing by measuring the optimum value of the write pre-competition amount in steps S1 to S8 is performed for each of the plurality of composite heads provided in the head assembly 14 in FIG.

In the above embodiment, the case where the temperature sensor 3 for detecting the environmental temperature T is provided in the disk enclosure 10 as shown in FIG. 1 is taken as an example, but the temperature sensor 3 is connected to the control circuit board 11. It is needless to say that the environmental temperature T may be detected by installing on the printed circuit board. Further, as another embodiment of the present invention, since the characteristic of the write pre-competition amount WP with respect to the environmental temperature T is given by, for example, a straight line as shown in FIG. 6, the relational expression WP = AT + B of this straight line is determined. The write pre-competition amount WP may be obtained by calculation for the temperature T and set in the write pre-competition circuit 1.

[0047]

As described above, according to the present invention, even if the hysteresis curve of the magnetic disk medium changes due to the temperature and influences the non-linear bit shift and the error rate deteriorates, the apparatus using the temperature sensor can be used. The PRML method is used to monitor the ambient temperature of the PML system and change the write pre-competition amount to the optimum value according to the temperature, without causing adverse effects on adjacent tracks or increasing the amount of circuits due to changing the write current. The non-linear bit shift affected by the temperature change can be surely canceled to avoid a read error.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a block diagram of a magnetic disk drive to which the present invention is applied;

FIG. 3 is a block diagram of a write modulation unit, a read demodulation unit, and a servo demodulation unit provided in the read channel circuit of FIG. 2;

FIG. 4 is a functional block diagram of an embodiment of the present invention for changing a write pre-competition amount using table information.

FIG. 5 is a characteristic diagram of a write pre-competition amount and an error rate with respect to an environmental temperature.

FIG. 6 is a characteristic diagram of a write / pre-competition amount with respect to an environmental temperature;

FIG. 7 is an explanatory diagram of table contents in FIG. 4;

FIG. 8 is a flowchart of a write pre-competition process of FIG. 4;

FIG. 9 is a functional block diagram of another embodiment of the present invention in which test data is written to a magnetic disk medium to measure and change a write pre-competition amount;

FIG. 10 is a flowchart of a write / pre-competition state in FIG. 9;

FIG. 11 is an explanatory diagram of a conventional non-linear bit shift that occurs at the time of writing and recording and at the time of reading;

FIG. 12 is an explanatory diagram of a nonlinear bit shift compensated by a conventional write pre-competition.

FIG. 13 is an explanatory diagram of a history curve of a magnetic disk medium that changes with temperature.

[Explanation of symbols]

 1: write / pre-competition circuit 2: setting processing unit 3: temperature sensor 4: table 5: test write / read instruction unit 6: error rate measurement unit 7: optimum value setting unit 10: disk enclosure 11: control circuit board 12: R / W preamplifier circuit 14: Head assembly 15: Voice coil motor (VCM) 16: Spindle motor 18: MCU (micro controller unit) 20: Read channel circuit (RDC) 22: Oscillator 24: Hard disk controller (HDC) 26: Flash PEROM 28: Data buffer 30: Servo controller 32, 34: FPC 36: Interface connector 40: Parallel interface 42: 8/9 encoder 44: Precoder 48: Write FF 50: Read channel Your Logic 52: AGC amplifier 54: programmable filter 56: full-wave rectifying circuit 58: AGC charge pump circuit 60: Adaptive equalizer 62: maximum likelihood detector 64: 8/9 decoder 66: PLL circuit

Claims (3)

(57) [Claims] 1. A storage device for writing information to be demodulated by partial response maximum likelihood detection on a medium, wherein a write current switching point for providing a next magnetization reversal interval following a long magnetization reversal interval and a short magnetization reversal interval. The write pre-compensation circuit compensates for the peak position of the read signal shifted at the time of reading by delaying the timing of the read signal by a predetermined write pre-competition amount in advance, and the environmental temperature detected by the temperature sensor. A setting processing unit for setting the write pre-competition amount of the write pre-competition circuit to an optimum value in response to the setting. 2. The storage device according to claim 1, wherein said setting processing unit has a table in which an optimum value of a write pre-competition amount corresponding to said environmental temperature is stored in advance, and said table is detected by said temperature sensor. A storage device, wherein an optimum value of a write pre-competition amount is read by referring to the table according to an environmental temperature and set in a write pre-competition circuit. 3. The storage device according to claim 1, wherein the temperature is
Degree sensor is mounted on the disk enclosure or print base.
A storage device characterized by being installed on a plate .