JPH0668657A - Information memory - Google Patents

Abstract

PURPOSE:To eliminate a stand-by time after identifying an ID part and to reduce an unused part between the ID part and a data part by properly selecting a distance between a recording head and a reproducing head and a detection delay time in a maximum likelihood decoder. CONSTITUTION:After a signal from the reproducing head is amplified by a reproduction amplifier 5, is equalized to a waveform of a partial response by an equalizer, 6. A recording code series whose error from an ideal waveform becomes a minimum is selected. The selected recording code series is converted to a data series by a demodulator 8. A distance between a gap center in the recording head and the gap center of the reproducing head is defined (x), a relative speed between the head 3 and a recording medium 4 as (v), a total time from when recording data on the medium 4 is read by the reproducing head to delay time of the equalizer 6 as T. Then, when T>x/v is satisfied, though recording is started immediately after ID identification is ended, the ID part is not rewritten.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information storage device such as a magnetic disk, and particularly to an information storage using a head in which a recording head and a reproducing head are separated and a maximum likelihood decoding method as a reproduction data detecting method. Regarding the device.

[0002]

2. Description of the Related Art As one of the techniques for increasing the density of a magnetic disk, an MR head capable of reproducing information on a medium at a high track density is known. MR
Since the head is exclusively for reproduction, it is necessary to use an inductive recording head together. Normally, the recording head is provided separately from the reproducing MR head in the rear of the traveling direction of the recording medium (Japanese Society of Applied Magnetics, Vol. 15, No. 2, p. 141, issued in April 1991, or 1990). IEEE TRANSACT issued in September
IONS ON MAGNETICS Vol. MAG
-26 No. 51689).

Another technique for increasing the density is
The method of equalizing the reproduced signal from the head into the partial response waveform, detecting the most probable recording code from the equalized waveform using the maximum likelihood decoding method, and reproducing the data from the code by the demodulator is the conventional method. It is known that data can be reproduced from a signal having an S / N lower than that of the peak detection method (IEEE TRA, issued in May 1985).
NSACTIONSON COMMUNICATION
S Vol. COM-34 No. 5 454 pages, or US Patent 4,6, issued February 1987.
44,564).

Further, when recording information on a magnetic disk, the ID section in which the address information of the sector is recorded is read and identified, and when it matches the target sector, the information is recorded in the data section immediately after that. Record.

[0005]

When recording information on a magnetic disk having a structure in which the recording head is separately provided behind the reproducing head in the traveling direction of the recording medium,
When the reproducing head identifies the ID information of the sector and the recording head performs recording immediately after that, the position of the recording head at that time may still be in the ID section and the information in the ID section may be rewritten. There was a problem that they had to be matched.

In a magnetic disk drive using the maximum likelihood decoding method, a plurality of types of possible code sequences must be stored in a path memory, so that the read head reads the information on the medium before the maximum likelihood. It takes a relatively long time for the decoder to detect the recorded code, and the sector ID
When the section is identified, the head moves away from the ID section and I
There is a problem that an unused area is formed between the D section and the data section.

An object of the present invention is to provide an information storage device in which a recording head and a reproducing head are separately provided and which uses a maximum likelihood decoder, and a distance between the recording head and the reproducing head and a detection delay of the maximum likelihood decoder. By selecting the time appropriately, ID
An object of the present invention is to provide an information storage device capable of reducing the unused area between the ID section and the data section without waiting time after identifying the section.

[0008]

In the information storage device of the present invention, the recording head is provided separately from the reproducing head at the rear of the traveling direction of the recording medium, and the reproduced signal from the reproducing head has a desired waveform. To the maximum likelihood decoder that detects the most probable recording code from the output of this equalizer, the demodulator that converts the output code of this maximum likelihood decoder into data, and the demodulator An information storage device comprising an ID identifier for identifying the ID information of a sector in the output data, wherein the distance between the recording head and the reproducing head is x, the relative speed between the head and the medium is v, and the reproducing head is on the medium. When the total delay time of the equalizer, maximum likelihood decoder, demodulator, and ID discriminator after reading the recorded data is T, a relation of T> x / v is established between them. To do.

[0009]

Next, the operation of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an information storage device of the present invention.
2 is an enlarged view of the head / recording medium portion of the information storage device of FIG. In these figures, 1 is a modulator, 2 is a recording amplifier, 3 is a magnetic head, 4 is a recording medium, 5 is a reproduction amplifier, 6 is an equalizer, 7 is a maximum likelihood decoder, 8 is a demodulator, and 9 is a demodulator.
Indicates an ID discriminator.

The magnetic head 3 is composed of a recording head and a reproducing head, and the recording head is arranged behind the reproducing head with respect to the medium running direction. The recording head and the reproducing head are independently designed for recording and reproducing, and are suitable for higher density than recording and reproducing with the same head. In particular, it is more preferable to use an MR head as the reproducing head because reproduction with high sensitivity is possible.

As the reproduction signal processing, a partial response and a maximum likelihood decoding method which can reproduce data from a low S / N signal with high reliability are used. The signal from the reproducing head is amplified by the reproducing amplifier 5 and then equalized by the equalizer 6 into a partial response waveform. From the equalized waveform, the maximum likelihood decoder 7 selects a recording code sequence that minimizes the error between the possible recording code sequence and the ideal waveform. The selected recording code sequence is converted into a data sequence by the demodulator 8. In the process of this reproduction signal processing, in order to select the optimum recording code especially in the maximum likelihood decoder, it is necessary to store a plurality of possible recording code sequences in the path memory. It takes a relatively long time from the reading of the information of 1 to the detection of the recording code by the maximum likelihood decoder.

On the recording medium 4, sector address information is recorded in the ID portion of each sector according to a predetermined format. When recording information in the data part of a sector, the sector address information of the ID part is read and the ID discriminator 9 judges whether or not the address information is equal to the specified sector address. To record.

The distance between the gap center of the recording head and the gap center of the reproducing head is x, the relative velocity between the head and the medium is v, and the equalizer, maximum likelihood decoder, after the recording data on the medium is read by the reproducing head, Let T be the total delay time of the demodulator and the ID discriminator. When the reproducing head reaches the end position of the ID section on the recording medium, the recording head moves a distance x
In front. When the determination as to whether the address information of the ID portion is equal to the designated sector address is finished (when ID identification is finished), the time T is delayed from the time when the reproducing head reaches the end position of the ID portion on the recording medium. When T> x / v (1) holds, the recording head is positioned vT-x behind the end position of the ID portion of the recording medium when the ID identification is completed. Therefore, if the condition of Expression (1) is satisfied, the ID portion is not rewritten even if recording is started immediately after the ID identification is completed.

In the case of a magnetic disk device, the relative speed v differs depending on the radius of the recording track. There is also known a method of increasing the storage capacity of the magnetic disk by increasing the recording frequency on the outer peripheral side of the track, but in this case, the delay time T differs depending on the recording track radius. In such a case, it is necessary that the condition of Expression (1) is satisfied for all track radii.

Within the range where the condition of the expression (1) is satisfied, the smaller T is, the smaller the unused area can be. But,
If the delay time in the maximum likelihood decoder is shortened, it may happen that the code must be output before the accurate judgment can be made, so it is not preferable to make it too short. Therefore, it is more preferable to select T as small as possible within the range where the condition (1) is satisfied and the performance of the maximum likelihood decoder can be maintained.

[0016]

EXAMPLES Examples of the present invention will be described in detail below. In the magnetic disk device having the configuration of FIG. 1, as the magnetic head 3, a shield type MR head and an inductive thin film head are laminated. The distance x between the reproducing MR head gap center and the recording head gap center is 10 μm.
m. A 3.5-inch disk is rotated at 3600 rpm, and the relative speed v at the innermost circumference is 8.5 m / s,
The data transfer rate was 4 MB / s. The modulation method used was 8/9 modulation, which converts 8 bits of data into 9 code words.
The equalizer 6 uses a digital transversal filter after A / D conversion of the signal after reproduction and amplification,
Equalized to partial response waveform. As the maximum likelihood decoder, a Viterbi decoder that determines the recording code from the difference between the two-state path metrics is used. Delay time at the equalizer is 167
ns, the maximum likelihood decoder has a delay time of 555 ns, the demodulator has a delay time of 250 ns, and the ID discriminator has a delay time of 2
50 ns, and the total T of these delay times is 1.22.
The relationship of T> x / v (= 1.176 μs) is established at 2 μs. Under this condition, even if data was recorded immediately after ID identification from the innermost circumference to the outermost circumference, the ID part was not rewritten. Further, in the innermost circumference, the unused area between the ID part and the data part was 0.387 μm, which was sufficiently small.

[0017]

As described above, the information storage device of the present invention discriminates the ID part by appropriately selecting the distance between the recording head and the reproducing head and the detection delay time of the maximum likelihood decoder. There is no waiting time, and the unused area between the ID part and the data part can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an information storage device of the present invention.

FIG. 2 is an enlarged view of a head / recording medium portion of the information storage device of FIG.

[Explanation of symbols]

 1 modulator 2 recording amplifier 3 magnetic head 4 recording medium 5 reproducing amplifier 6 equalizer 7 maximum likelihood decoder 8 demodulator 9 ID discriminator

Claims (1)

[Claims] 1. An equalizer, wherein a recording head is provided separately from a reproducing head at a rear side in a traveling direction of a recording medium, and an equalizer for converting a reproduced signal from the reproducing head into a desired waveform.
A maximum likelihood decoder for detecting the most probable recording code from the output of this equalizer, a demodulator for converting the output code of this maximum likelihood decoder into data, and a sector ID in the data at the output of this demodulator In an information storage device including an ID identifier for identifying information, the distance between the recording head and the reproducing head is x, the relative speed between the head and the medium is v, and the above-mentioned after the recording data on the medium is read by the reproducing head. An information storage device characterized in that when the total delay time of the digitizer, the maximum likelihood decoder, the demodulator and the ID discriminator is T, a relation of T> x / v is established between them.