JPH05135509A - Centering control system for data window - Google Patents

Abstract

PURPOSE:To exactly read data despite the variance of the head characteristic by performing the optimum shift of the position of a date window based on the phase difference between the data window and the allowable read clock signal of each head. CONSTITUTION:A measuring means 112 measures an allowable phase difference range set between a read clock signal and a date window for plural magnetic heads 101. A phase difference deciding means 113 decides the optimum phase difference between the read clock signal and the data window based on the range set for each head 101. A holder means 114 holds the obtained optimum phase difference. A phase shift means 115 shifts the data window by an extent equal to the corresponding phase difference held in the means 114 in response to an input of a read instruction. Then the demodulation processing is carried out by a demodulator means 111. In such a constitution, the phase shift extent is controlled in consideration of the variance of characteristics of the heads 101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data window centering adjustment method for adjusting a phase shift between a data window and data read from a magnetic head when reproducing data recorded on a recording medium such as a magnetic disk. Regarding

In the present specification, the data window means a section from the falling edge of the read clock signal to the next falling edge, and the decoder, which is the demodulating means of the magnetic disk device, reads from the magnetic head for each data window. Of the read data is detected, and the recorded data is demodulated.

On the other hand, with the recent increase in the scale of computer systems, there is a demand for larger capacity of magnetic disk devices, and it is necessary to record data at high density on a recording medium and reproduce the data without error. Is required. Therefore, there is a need for a technique for precisely adjusting the phase shift between the data window and the read data so that the rising position of the read data is at the center of the data window.

[0004]

2. Description of the Related Art FIG. 4 is an explanatory diagram of a reproducing process of data recorded on a magnetic disk. As shown in Fig. 4, two peaks due to magnetization reversal (shown by dotted lines in Fig. 4 (b)) corresponding to rising and falling of the pulse (see Fig. 4 (a)) applied to the magnetic head during recording. 4) interferes with each other, so that the peak position of the waveform of the read data is deviated from the original magnetization reversal position as shown by the solid line in FIG. 4 (b). Further, such a shift in the peak position changes depending on the pattern of the adjacent magnetization reversal and also changes depending on the characteristics of the magnetic head. Therefore, depending on the characteristics of the magnetic head, when reading data of a specific pattern There is a case that the phase shift between the read data and the data window becomes large and reproduction becomes impossible.

Therefore, conventionally, a phase shift range (hereinafter referred to as a reproducible range) in which any of a plurality of magnetic heads provided in a magnetic disk device can reproduce recorded data without error is obtained, and the phase is calculated. The phase shift amount of the data window was determined and set in the decoder so that both the lead side (EARLY) side and the phase lag side (LATE) side had the same phase margin. In this case, as shown in FIG. 5, the decoder performs reproduction processing by changing the duty ratio of the read clock signal to shift the data window position by the set phase shift amount.
If the characteristics of each magnetic head are almost the same, the data recorded on all magnetic disks can be reproduced without error.

In some cases, the phase margin is measured for each of the plurality of magnetic heads, and the phase shift amount determined based on the average value is set in the decoder.

[0007]

By the way, a plurality of magnetic heads provided in a magnetic disk device actually have their own characteristics. Due to variations in these characteristics, the optimum position of the data window is It is different for each magnetic head. When the recording density on the magnetic disk is low, the optimum position difference for each magnetic head is sufficiently smaller than the width of the data window. There is no problem in assuming that it is the characteristic of. However, as the recording density increases, the above-mentioned variation in the optimum position of the data window becomes a size that cannot be ignored as compared with the width of the data window.

Therefore, if a uniform phase shift amount is set in the decoder regardless of variations in the characteristics of each magnetic head, the phase margin to the EARLY side or the LATE side becomes extremely small depending on the magnetic head, and the magnetic Due to subtle fluctuations in the rotation speed of the disk and minute deviations in the magnetic head position, the synchronization between the data window and the read data may be lost, making it impossible to perform data reproduction processing.

It is an object of the present invention to provide a data window centering adjustment method for adjusting the phase shift of the data window in consideration of the difference in the characteristics of the plurality of magnetic heads.

[0010]

FIG. 1 is a block diagram showing the principle of the present invention. According to the present invention, in response to the input of a read instruction designating one of the plurality of magnetic heads 101, the demodulation means 111 causes the designated magnetic head 101 for each data window having a predetermined phase relationship with the read clock signal.
A plurality of magnetic heads 1 are used in a disk controller that detects read data from a disk and demodulates data recorded on the magnetic disk 102 corresponding to the magnetic head 101.
For each 01, in order to make it possible to demodulate the data recorded on the corresponding magnetic disk 102, a measuring means 112 for measuring the range of the phase difference allowed between the read clock signal and the data window, and a plurality of magnetic fields. Head 1
01, the phase difference determination means 113 for determining the phase difference that the read clock signal and the data window should have based on the range obtained respectively, and the phase difference determination corresponding to each of the plurality of magnetic heads 101. Means 113
The holding means 114 for holding the phase difference obtained in step (1) and the phase to be used for demodulation processing by the demodulation means 111 by shifting the data window by the corresponding phase difference held in the holding means 114 in response to the input of the read instruction. And a shift means 115.

[0011]

According to the present invention, the measuring means 112 obtains the measurement result reflecting the characteristics of each magnetic head 101, and the phase difference determining means 113 optimizes the read clock signal and the data window corresponding to the magnetic head 101. The phase difference is determined and held in the holding means 114. Therefore, according to the read instruction, the phase shift means 115 shifts the data window by the phase difference obtained by searching the holding means 114, and the corresponding magnetic head 101.
It is possible to automatically adjust the phase shift of the data window in accordance with the characteristic of (3), and the demodulation means 111 can be provided with the data window shifted to the optimum position.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows an embodiment configuration of a disk control device to which the data window centering adjustment method of the present invention is applied.

In FIG. 2, a magnetic disk device 201
Includes a plurality of magnetic disks 102 and a magnetic head 101 corresponding to these magnetic disks 102.

Further, the disk control unit 210 includes an encoder 213 and a decoder in accordance with a write command and a read command input from a host computer (not shown) by the microprocessor (MPU) 211 via the interface circuit 212. 214 and magnetic head drive unit 215
Is controlled to access the magnetic disk device 201.

The above-mentioned magnetic head drive unit 215 moves the designated magnetic head 101 to the designated cylinder position in accordance with an instruction from the microprocessor 211, and outputs the output of the encoder 213 in response to a writing instruction. Is sent to the designated magnetic head 101, and the read data from the corresponding magnetic head 101 is sent to the decoder 214 according to the read instruction.

Further, the phase shift circuit 216 adjusts the duty ratio of the read clock signal according to an instruction from the microprocessor 211 (see FIG. 5) and supplies the obtained read clock signal to the decoder 214. The data window used for reproducing the read data is shifted.

Since an LSI device for data demodulation having the function of the phase shift circuit 216 is commercially available,
This LSI element may be used as the decoder 214 and the phase shift circuit 216 described above.

In FIG. 2, the RAM 217 is connected to the microprocessor 211 so that it can be accessed. Further, the comparison unit 218 compares the demodulated data obtained by the above-described decoder 214 with the data held in the register 219 and determines whether or not they match with each other by the microprocessor 2
11 is notified.

A method of measuring the reproducible ranges of a plurality of magnetic heads 101 and obtaining the optimum phase shift Ss indicating the optimum data window position from the reproducible ranges will be described below.

FIG. 3 is a flow chart showing the reproducible range measuring process and the phase shift determining process. Here, for the evaluation of the reproducible range, it is appropriate to use a bit pattern that is highly likely to be unable to be accurately demodulated. As such a bit pattern, a peak shift due to interference from an adjacent pattern (indicated by symbol ΔX in FIG. 5) and a magnetization reversal interval (indicated by symbol b in FIG. 5) are provided for each encoding method. The worst pattern that maximizes the ratio ΔX / b is empirically known. Therefore, this worst pattern may be held in the worst pattern holding area 221 of the RAM 217, and the worst pattern may be set in the register 219 via the microprocessor 211.

When the magnetic head 101 reads data from an arbitrary cylinder of the corresponding magnetic disk 102, the interference from not only the pattern recorded in the cylinder but also the data recorded in the surrounding cylinders. Since it is also affected, the optimum phase shift is the magnetic disk 1
It is different for each 02 cylinder. Therefore, in the following processing, in addition to the variation in the characteristics of the magnetic heads 101, the influence of the magnitude of the data interference at each cylinder position of the magnetic disk 102 is also evaluated.

For example, when installing the magnetic disk device 201 and the disk control device 210, the microprocessor 211 first reads the worst pattern from the RAM 217 and sets it in the encoder 213. In addition, the i-th magnetic head 1 is connected to the magnetic head driver 215.
01 (hereinafter referred to as the magnetic head 101 _i ) and the j-th cylinder position are designated, and the magnetic head drive unit 21
5 and the encoder 213 are instructed to perform a write operation, and the modulated data corresponding to the worst pattern is written on the corresponding magnetic disk 102 (step 301). Here, the microprocessor 211 sets the variables i and j indicating the order of the magnetic head 101 and the cylinder position to, for example,
The initial value “1” may be set in advance.

After that, the microprocessor 211 makes the EA
The maximum phase shift S _maxE to the RLY side is _set to the phase shift circuit 21.
6, the data window is shifted (step 302), the magnetic head 101 _i and the j-th cylinder position are designated, the magnetic head drive unit 215 and the decoder 214 are instructed to perform a read operation, and data is read. (Step 303).

In response to this, the read data from the magnetic head 101 _i is input to the decoder 214 via the magnetic head drive unit 215, and the demodulation result by the decoder 214 is sent to the comparison unit 218 and held in the register 219. It is compared with the worst pattern that was done.

If the comparison unit 218 determines that the demodulation result and the worst pattern do not match, step 30
4 becomes a negative determination, and the microprocessor 211
Is a new phase shift S obtained by subtracting a predetermined change α from the phase shift S, sets the updated phase shift S in the phase shift circuit 216 (step 305), and returns to step 303.

As described above, when the data read operation is performed while the phase shift S is sequentially reduced and the worst pattern is obtained as the demodulation result, the affirmative determination is made in step 304. In this case, the microprocessor 211
Holds the phase shift S at this time as the maximum allowable EARLY-side allowable phase shift Se when the magnetic head 101 _i reproduces the data recorded in the j-th cylinder (step 306).

Next, the microprocessor 211 obtains and holds the allowable phase shift Sl on the LATE side in the same manner as in steps 302 to 305 (step 307).
In this way, the allowable phase shifts Se and LA on the EARLY side are
As the allowable phase shift Sl on the TE side, a reproducible range in which the data recorded in the j-th cylinder can be accurately demodulated by using the magnetic head 101 _i can be obtained. That is, the worst pattern holding area 221 of the encoder 213, the decoder 214, the phase shift circuit 216, and the RAM 217.
The functions of the measurement unit 112 are realized by the respective units of the comparison unit 218 and the register 219 operating according to an instruction from the microprocessor 211.

Next, the microprocessor 211 operates as the phase difference determining means 113 and finds the optimum phase shift Ss for setting the data window at the center of the above-mentioned reproducible range (step 308). At this time, the microprocessor 211 sets the sign of the allowable phase shift Se on the EARLY side as positive and the sign of the allowable phase shift Sl on the LATE side as negative, and averages the above-mentioned allowable phase shift Se and allowable phase shift Sl. Calculate the value and use this average value as the optimum phase shift
You can use Ss. Further, the RAM 217 stores the holding means 11
4, a phase shift table 222 is provided, and the microprocessor 211 corresponds to the magnetic head 101 and the cylinder position, and the optimum phase shift described above is performed.
Ss may be held in this phase shift table 222.

Next, the variable j is incremented (step 309) and it is judged whether or not the value of the variable j exceeds the total number M of the cylinders of the magnetic disk 102 (step 31).
0), the above-described steps 301 to 310 are repeated until the affirmative determination is made in step 310. On the other hand, in the case of affirmative determination in step 310, the variable i is incremented (step 311), it is determined whether or not the value of the variable i exceeds the total number N of the magnetic heads 101 (step 312), and this step 312 The above-described steps 301 to 312 are repeated until the affirmative determination is made, and when the affirmative determination of step 312 is made, the process may be ended.

As a result, when each magnetic head 101 is located at each cylinder position on the magnetic disk 102, the optimum phase shift Ss that gives the phase difference that the data window and the read clock signal should have is obtained, and the phase shift table 22 is obtained.
2 can be held corresponding to the magnetic head 101 and the cylinder position.

Next, the access processing performed by the disk control device 210 with respect to the magnetic disk device 201 in response to an instruction from the host computer will be described. When a write command is input from the host computer via the interface circuit 212, the microprocessor 211 responds to the write command to instruct a data write operation as in the conventional case, and responds to this. Encoder 21
The output of No. 3 is written in the designated cylinder by the corresponding magnetic head 101.

On the other hand, when a read command is input, the microprocessor 211 first refers to the phase shift table 222 of the RAM 217 and refers to the optimum phase shift corresponding to the magnetic head 101 and the cylinder position designated by the read command.
After searching Ss and setting it in the phase shift circuit 216,
As in the conventional case, the corresponding magnetic head 101 and cylinder position are designated and a read operation is instructed. Accordingly
The read data from the corresponding magnetic head 101 is input to the decoder 214, and demodulation processing is performed using the data window whose phase is shifted by the phase shift circuit 216.

In this way, the phase shift circuit 216
However, the decoder 2 corresponding to the demodulation means 111 operates by operating in accordance with an instruction from the microprocessor 211.
It is possible to provide 14 with a data window provided with a phase shift corresponding to the magnetic head 101 and cylinder position designated by the read instruction. That is, the function of the phase shift means 115 is realized by the phase shift circuit 216 and the microprocessor 211, and as a whole, the phase shift of the data window is automatically adjusted in consideration of the characteristics of the magnetic head 101. Is possible.

As a result, the position of the data window can be adjusted to the optimum position when the arbitrary magnetic head 101 is located at the arbitrary cylinder position. It is possible to guarantee the synchronization between the data window and the read data regardless of the magnitude of the interference. Therefore, the data recorded at a high density on the magnetic disk can always be correctly reproduced, so that the magnetic disk device 2
01 reliability can be improved.

If the difference in the magnitude of interference from the peripheral cylinders at each cylinder position is sufficiently small as compared with the variation in the characteristics of the magnetic head 101, the measuring means 112.
Is the magnetic disk 1 to which each magnetic head 101 corresponds.
The measurement process described above may be performed at any of the cylinder positions 02, and the measurement result may be applied to all the cylinder positions.

[0036]

As described above, according to the present invention, when each of the plurality of magnetic heads reproduces the data recorded on the magnetic disk, it is based on the allowable phase difference between the read clock signal and the data window. Since the data window position used for the demodulation process of the read data from each magnetic head can be automatically set to the optimum position, even if there are variations in the characteristics of the magnetic head, the data recorded at high density can be accurately recorded. Therefore, the reliability of the magnetic disk device can be improved.

[Brief description of drawings]

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

FIG. 2 is a block diagram of an embodiment of a disk control device to which the system of the present invention is applied.

FIG. 3 is a flowchart showing a reproducible range measuring operation and an optimum phase shift determining operation.

FIG. 4 is an explanatory diagram of a reproduction process of data recorded on a magnetic disk.

FIG. 5 is an explanatory diagram of a data window shift process.

[Explanation of symbols]

 101 magnetic head 102 magnetic disk 111 demodulation means 112 measurement means 113 phase difference determination means 114 holding means 115 phase shift means 201 magnetic disk device 210 disk control device 211 microprocessor (MPU) 212 interface circuit 213 encoder 214 decoder 215 magnetic head drive unit 216 Phase shift circuit 217 RAM 218 Comparison unit 219 Register 221 Worst pattern holding area 222 Phase shift table

Claims (1)

[Claims] 1. A demodulating means (11) in response to an input of a read instruction designating one of a plurality of magnetic heads (101).
1) designates a designated magnetic head (10) for each data window having a predetermined phase relationship with the read clock signal.
1) detecting read data from the magnetic head (1)
01) in a disk controller for demodulating data recorded on a magnetic disk (102), the data recorded on the corresponding magnetic disk (102) is demodulated for each of the plurality of magnetic heads (101). Measuring means (112) for measuring the range of the phase difference allowed between the read clock signal and the data window, and the range obtained corresponding to each of the plurality of magnetic heads (101). Corresponding to each of the plurality of magnetic heads (101), the phase difference determining means (113) for obtaining the phase difference between the read clock signal and the data window,
Holding means (114) for holding the phase difference obtained by the phase difference determining means (113), and the holding means (114) in response to the input of the read instruction.
A data window centering adjustment method comprising: a phase shift means (115) for shifting the data window by the corresponding phase difference held in the step (1) and performing the demodulation processing by the demodulation means (111).