JPH05282612A - Magnetic disk unit - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a peak shift correction table in a magnetic disk device, and refers to this peak shift correction table before writing data to write data of various patterns. It is characterized in that the peak shift amount can be always reduced by pre-shifting the write data according to the bit interval. [Structure] In a magnetic disk device of the present invention, a host CPU
20 to 1-7 RLL code write data and 1-7
Bit interval data regarding the bit interval of the RLL code is supplied to the controller 14. In the controller 14, the write data is supplied to the write circuit 13. Further, the peak shift correction table stored in the memory 15 is referred to based on the bit interval data, and the selection signal is output to the writing circuit 13 according to the reference result. The write circuit 13 preshifts the write data in a predetermined direction according to the selection signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device used as a data recording / reproducing device in a computer system or the like.

[0002]

2. Description of the Related Art Conventionally, a hard disk drive (HD
In order to correct the peak shift caused by the interference of the signal waveform, the writing circuit used in the magnetic disk device such as D) is opposite to the direction of the peak shift on the time axis before writing the data to the recording medium. A pre-shift circuit for pre-shifting write data in the direction of is provided.

[0003]

Generally, a method of correcting the peak shift by improving the frequency response of the reproducing circuit and increasing the gain in the high frequency region is used. In recent years, in hard disk drives, research and development has been carried out so that desirable characteristics can be obtained by maximizing the characteristics of the reproducing circuit described above while suppressing the characteristics of the magnetic head medium, which increases recording density and costs. Has been done. By the way, the correction of the peak shift by the reproducing circuit is performed by the waveform equalizing circuit, but if the circuit is provided corresponding to the characteristics of the magnetic head medium or the repetition frequency of the write signal, the circuit configuration becomes large. I will end up.

FIG. 4 is a diagram showing measurement results of peak shift amounts at various bit intervals when data of a random pattern by the 1-7 RLL code is recorded in a hard disk drive having a conventional waveform equalization circuit.
The vertical axis represents the peak shift amount (%). In this measurement, eight magnetic heads are used.

In the 1-7 RLL code, when the interval of 1-bit cells is T, the bit interval exists from 2T to 8T. 41, the leftmost result is data 10100001 of a pattern in which bit intervals 2T and 5T are repeated.
Shown is the peak shift amount in the bit interval 2T when recording 010000 ..., and the other results are the peak shift in the bit interval 2T to 8T existing in the 1-7RLL code when recording random pattern data. Shows the amount. Note that, for example, a bit interval of 2T means that there is one bit 0 between a certain bit 1 and the next bit 1, and a bit interval of 5T means a certain bit 1 This means that there are four bits 0 between the next bit 1 and the next bit 1.

As can be seen from FIG. 4, the bit interval is 2T.
In the above, the peak shift occurs in the direction in which the bit interval is widened due to the waveform interference, that is, in the forward direction (+ direction) in time. However, if the bit interval is 3T or more, conversely,
The peak shift occurs in the direction in which the bit interval becomes narrow, that is, in the time delay direction (-direction). Note that FIG. 4 shows the measurement results when data of a random pattern is recorded, so even if the bit interval is 3T, the bit interval is 2T.
-3T combination and bit interval 3T-4T 3T
Since there are two possible combinations of a long bit interval and a short bit interval, an accurate analysis cannot be made.

FIG. 5 is a diagram showing the measurement results of peak shift amounts for short bit intervals and long bit intervals in each repetitive pattern when data of a repetitive pattern having only a predetermined pattern is recorded. Here, the short bit interval means, for example, a bit interval 2T when the bit interval of the data of the repeating pattern is a combination of 2T-4T, and the long bit interval means the bit interval 4T in the case of this combination. means. In this measurement, four magnetic heads are used.

As can be seen from FIG. 5, in combination with other bit intervals when the short bit interval is 2T,
The peak shift occurs in the advancing direction (+ direction), that is, in the direction in which the bit interval increases. However, in the combination with other bit intervals when the short bit interval is 3T or more, peak shift occurs in the delay direction (-direction), that is, in the direction in which the bit interval becomes narrow.

Therefore, from the above results, when the above-described pre-shift circuit is used, the peak shift occurs in the advance direction in the data of the pattern with the bit interval 2T, so that the peak shift amount can be reduced. In the case of data having a pattern having a bit interval of 3T or more, peak shift occurs in the delay direction, so there is a problem that the peak shift amount increases in the delay direction.

The present invention has been made for the above reasons, and an object of the present invention is to magnetically write data of various patterns which can be pre-shifted so as to always reduce the peak shift amount. It is to provide a disk device.

[0011]

A magnetic disk device according to the present invention comprises a recording medium, a storage means for storing a shift code indicating a shift direction of a peak shift corresponding to a combination of bit intervals of write data, and a writing means. When the embedded data is recorded on the recording medium, a shift code is read from the recording medium according to a bit interval of the write data, and a pre-shift direction of the write data is determined according to the read shift code, and the determined pre-shift direction. And a means for pre-shifting the write data and a means for recording the pre-shifted write data on a recording medium.

[0012]

With the above-described structure, a peak shift correction table is prepared, and the correction table is referred to before writing the data so that the write data can be written in correspondence with the bit intervals of the write data of various patterns. By pre-shifting, the peak shift amount can always be reduced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing the configuration of a magnetic disk device according to an embodiment of the present invention. In FIG.
The magnetic disk device includes a recording medium 10 and a magnetic head 1.
1, read circuit 12, write circuit 13, controller 14,
And a memory 15.

The recording medium 10 is, for example, a magnetic disk and records various data. The magnetic head 11 writes / reads data to / from the recording medium 10. The data recorded on the recording medium 10 is read as a reproduction signal by the magnetic head 11 and supplied to the reading circuit 12. In the read circuit 12, the reproduction signal from the magnetic head 11 is differentiated, the zero cross point of the differentiated signal is detected,
As a result, read pulse data is generated as read data. This read data is sent to the host CP included in a host system (not shown) via the controller 14.
It is output to U20.

When writing data to the recording medium 10, the host CPU 20 outputs to the controller 14 the write data according to the 1-7 RLL code and the bit interval data regarding the bit interval of the 1-7 RLL code.

Under the control of the host CPU 20, the controller 14 controls the entire magnetic disk device, transmits / receives data to / from the host system, and the like. Further, the controller 14 allows the host C
The write data by the 1-7 RLL code output from the PU 20 and the bit interval data regarding the bit interval of the write data are received. The write data based on the 1-7 RLL code is supplied to the write circuit 13. Further, the peak shift correction table stored in the memory 15 is referred to based on the bit interval data, and the selection signal is output to the writing circuit 13 according to the reference result.

As described above, the memory 15 writes the write data so as to reduce the peak shift amount in accordance with the bit interval of the write data of various patterns by the 1-7 RLL code when writing the data. A peak shift correction table used for pre-shifting is stored (see FIG. 2). In FIG. 2, n represents the number of bits 0 between a predetermined bit 1 of the write data and a bit 1 existing immediately before it, and m represents a predetermined bit 1 of the write data and the next bit. It indicates the number of bit 0 existing between the bit 0 and the bit 0 existing in.

When the code E (EARLY) is referred to, since the shift direction of the peak shift is the time advance direction, the pre-shift is performed so as to shorten the bit interval of the write data. If the code N (NORMAL) is referred to, no preshift is performed. Code L
When (LATE) is referred to, the shift direction of the peak shift is delayed in time, so pre-shift is performed so as to lengthen the bit interval of the write data.
This peak shift correction table is preset or defined by the user. Also, it can be configured to be rewritable.

In the peak shift correction table shown in FIG. 2, the short bit interval is 2T (T is a bit cell) in the write data combination pattern based on the measurement results of FIGS. 4 and 5. Bit cell)
That is, when n = 1, the code is set so that the pre-shift is performed so as to shorten the bit interval, and when the bit interval is other than that, the pre-shift is performed so that the bit interval is increased. The code is set.

The write circuit 13 has a pre-shift circuit 13a and supplies a write current to the magnetic head 11 based on write data from the controller 14. Pre-shift circuit 13
The a pre-shifts the bit interval of the write data according to the selection signal from the controller 14.

FIG. 3 is a block diagram showing the structure of the preshift circuit 13a. In FIG. 3, the pre-shift circuit 1
3a is composed of delay circuits 30 and 31 and a selection circuit 32. In response to the selection signal from the controller 14,
Delay circuits 30 and 31 are selected. The delay circuit 30 outputs an EARLY signal for shortening the bit interval of the write data to the selection circuit 32. The delay circuit 31 also outputs a LATE signal for lengthening the bit interval of the write data to the selection circuit 32. The selection circuit 32 is the delay circuit 3
EARLY signal or LATE from 0 or 31
1-7 supplied from the controller 14 according to the signal
The write data by the RLL code is pre-shifted in the direction of delay (-direction) or the direction of advance (+ direction) with respect to time.

Next, the operation of the magnetic disk device of the present embodiment having the above configuration will be described.

At the time of writing data to the recording medium 10, the write data by the 1-7 RLL code and the bit interval data regarding the bit interval of the 1-7 RLL code are output from the host CPU 20 to the controller 14.

In the controller 14, the host CPU 20
The write data and the bit interval data of the write data according to the 1-7 RLL code output from are received. The write data based on the 1-7 RLL code is supplied to the write circuit 13. Also, based on the bit interval data, the memory 1
The peak shift correction table stored in 5 is referred to, and the selection signal is output to the writing circuit 13 according to the reference result. That is, when the code E (EARLY) is referred to by the bit interval data, the preshift circuit 1
The selection signal is output to the delay circuit 30 of 3a. Further, when the code L (LATE) is referred to by the bit interval data, the selection signal is output to the delay circuit 31 of the preshift circuit 13a.

In the pre-shift circuit 13a in the writing circuit 13, either one of the delay circuits 30 and 31 operates according to the selection signal output from the controller 14. That is, when the selection signal is supplied to the delay circuit 30, the EAR
The LY signal is output to the selection circuit 32. On the other hand, when the selection signal is output to the delay circuit 31, the LATE signal is output to the selection circuit 32.

The selection circuit 32 receives the EARLY signal or the LATE signal from the delay circuit 30 or 31. When the EARLY signal is received, the write data according to the 1-7 RLL code supplied from the controller 14 is pre-shifted in the direction delayed in time (-direction). As a result, the bit interval of the write data becomes narrow. On the other hand, when the LATE signal is received, the write data based on the 1-7 RLL code supplied from the controller 14 is pre-shifted in the forward direction (+ direction). This widens the bit interval of the write data.

The write data pre-shifted by the selection circuit 32 is written on the recording medium 10 by the magnetic head 11.

As described above, the peak shift correction table used for determining the pre-shift direction according to the bit intervals of the write data of various patterns is prepared, and the peak shift correction table is referred to when writing the data. By pre-shifting the write data in the predetermined direction, the peak shift amount can be always reduced.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention.

In this embodiment, only the peak shift direction is set in the peak shift correction table, but the peak shift amount can also be set, thereby further reducing the peak shift amount. be able to.

[0032]

As described above, according to the present invention, a peak shift correction table is prepared in the magnetic disk device, and the correction table is referred to before writing the data.
By preshifting the write data corresponding to the bit intervals of the write data of various patterns, it is possible to always reduce the peak shift amount.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a magnetic disk device that is an embodiment of the present invention.

FIG. 2 is a diagram showing the contents of a peak shift correction table stored in a memory of the magnetic disk device of this embodiment.

FIG. 3 is a block diagram showing the configuration of a pre-shift circuit included in the write circuit of the magnetic disk device of this embodiment.

FIG. 4 is a diagram showing a measurement result of a peak shift amount at each bit interval when data of a random pattern is recorded by a 1-7 RLL code in a hard disk drive having a conventional waveform equalization circuit.

FIG. 5 is a diagram showing measurement results of peak shift amounts for short bit intervals and long bit intervals in each repetitive pattern when data of a repetitive pattern having only a predetermined pattern is recorded.

[Explanation of symbols]

10 ... Recording medium, 11 ... Magnetic head, 12 ... Readout circuit,
13 ... Write circuit, 13a ... Pre-shift circuit, 14 ... Controller, 15 ... Memory, 20 ... Host CPU, 30,
31 ... Delay circuit, 32 ... Selection circuit.

Claims (2)

[Claims] 1. A recording medium, a storage means for storing a shift code indicating a shift direction of a peak shift corresponding to a combination of bit intervals of the write data, and a writing means for writing the write data in the recording medium. A shift code is read from the recording means according to a bit interval of the data, a means for determining a preshift direction of the write data according to the read shift code, a means for preshifting the write data according to the determined preshift direction, and a preshift And a means for recording the write data on a recording medium. 2. When the write data is composed of a 1-7 RLL code, the write data is pre-shifted so as to narrow the bit interval when the bit interval of the write data is twice the bit cell, and the write data is 2. The magnetic disk drive according to claim 1, wherein the write data is pre-shifted so as to widen the bit interval except when the bit interval is twice the bit cell.