JPH05347076A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To realize a device preventing mis-judgment even when S/N becomes wrong and having a privacy function by selecting the format of interleaving operation with a cipher code and selecting the format of inverse-interleaving operation with a decipher code. CONSTITUTION:When by an interleaving means 2, convolution coded data is interleaved with various kinds of formats, the format is selected by the cipher code from a cipher code input means 3 and recorded through a write amplifier 4. Further, at a reproducing time, a regenerative signal amplified by a read amplifier 5 is inverse-interleaved with various kinds of formats by an inverse- interleaving means 6. In such a case, the format is selected by the decipher code from a decipher code input means 7 and by a maximum likelihood decoding means 8, regenerative data is decoded while being error-corrected by a maximum likelihood decoding method. Thus, the mis-judgment due to viterbi equalization is prevented even when the S/N becomes wrong and the privacy function is effective for a person who knows no decipher code.

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, and more particularly to a magnetic disk device which decodes a reproduced signal from a magnetic head by using a maximum likelihood decoding method while performing error correction, and a secret process during error correction processing. The present invention relates to a magnetic disk device. In recent years, the S / N ratio of recording / reproducing signals has deteriorated and the intersymbol interference has increased with the downsizing and increasing the capacity of magnetic disk devices. In order to realize a highly reliable magnetic disk device under such severe conditions, an error correction technology for recording data is indispensable, and a magnetic disk device excellent in error correction for recording data is desired. .. Further, there is also a demand for confidential processing in which recorded data being error-corrected cannot be read by a third party without permission.

[0002]

2. Description of the Related Art Conventionally, intersymbol interference in magnetic recording and reproduction is regarded as a convolutional code, and demodulation is performed by a maximum likelihood decoding method, for example, a Viterbi decoding method. FIG. 7 shows the configuration of a conventional magnetic disk device. Recorded data is RL
It is encoded by an L (Run Length Limited Code) encoder 61, recorded on a magnetic disk 64 by a write amplifier 62 and a head 63, read by a head 65 during reproduction, amplified by a read amplifier 66, and then Viterbi equalized. The demodulated data was obtained by the converter 67 and the RLL combiner 68. In this Viterbi decoding method, the inter-code interference of the read signal from the magnetic disk 64 is equalized to reduce the data error.

However, in this Viterbi decoding method, if the S / N ratio of the read signal from the magnetic disk becomes poor, the number of erroneous determinations in the Viterbi equalization increases, so that the error propagates to the opposite side. There was a problem that the error rate was worse than that. Therefore, the present inventor writes the recorded data once by a convolutional code, writes it by using an interleave operation for changing the order of the time series of the code for each block, and corrects the Viterbi equalized reproduction signal by the reverse interleave operation at the time of reading. By returning to the time-series convolutional code and performing error correction decoding with a Viterbi decoder or a sequential decoder, even if the S / N ratio of the read signal from the magnetic disk deteriorates, an erroneous determination occurs in Viterbi equalization. I proposed a hard disk drive.

By the way, if the magnetic disk device is connected via a network, the recorded data may be read by a third party without permission. Therefore, in order to prevent the recorded data from being stolen, it is necessary to encrypt the recorded data in secret. Conventionally, the encryption and decryption program is used to process the data in software by using encryption. I was going.

[0005]

However, in the conventional confidential data processing in which software is used by using the recording data encryption and decryption program, the processing takes time, and the memory and data for performing the confidential data processing are required. There is a problem that a file for saving the file is required, the device becomes large and the cost increases.

Therefore, according to the present invention, the recording data is once encoded by a convolutional code, and the write signal is written by using an interleave operation in which the order of the time series of the code is changed for each block, and the read signal subjected to the Viterbi equalization is read by the deinterleave operation. In the magnetic disk device that returns to the correct time series convolutional code by the error correction decoding with the Viterbi decoder or the sequential decoder, the interleave processing that replaces the time series without using the encryption and decryption programs for the confidential processing,
By performing the secret story processing using the reverse interleave processing, even if the S / N ratio of the read signal from the magnetic disk becomes poor, it is unlikely that an erroneous determination will occur in Viterbi equalization, and the secret story processing is applied to eavesdropping. An object of the present invention is to provide a magnetic disk device that is free from the risk of being damaged.

[0007]

FIG. 1 shows the configuration of a magnetic disk device according to the present invention which achieves the above object. As shown in this figure, the present invention is a magnetic disk device which reproduces data recorded on a magnetic disk D by a magnetic head H and decodes a reproduced signal by a maximum likelihood decoding method. Convolutional encoding means 1 for converting into a convolutional code, and for the convolutionally encoded data,
An interleaving means 2 capable of performing an interleaving operation corresponding to a channel corresponding to a symbol of a convolutional code in various formats, and an encryption code input means 3 for inputting an encryption code for selecting a format in the interleaving operation to the interleaving means 2. A write amplifier 4 that amplifies the interleaved data and inputs it to the head H prepared for the channels, a read amplifier 5 that amplifies a reproduction signal from the head H prepared for the channels, and a read amplifier 5. Deinterleaving operation is performed on the reproduction signal from the device in various formats to return the reproduction signal to the convolutionally encoded reproduction data, and the decoding code for selecting the format in the deinterleaving operation is the deinterleaving means. Decoding to enter in 2 And over de input means 7, relative to the convolutional coded reproduced data, characterized by comprising a maximum likelihood decoding section 8 for decoding while the error correction by the maximum likelihood decoding method.

In the magnetic disk device, the recording data switching means 9 for time-dividing the recording data existing for the channels corresponding to the symbols of the convolutional code and transmitting the time-divided recording data to the interleaving means 2 for one channel, and the deinterleaving. It may further include multiplexer means 10 for returning the reproduction signal from the means 5 to the convolutional code for the channel in time division in synchronization with the operation of the recording data switching means 9.

[0009]

According to the magnetic disk device of the present invention, the error propagating at the time of Viterbi equalization is diffused by the operation of interleaving and approaches a random error. Then, strong error correction is performed in the decoding stage of the convolutional code, and by performing the interleave operation in this way, the defect of the convolutional code, which is weak against burst errors, is compensated, and the deterioration of the error correction capability is minimized. ..
Then, the interleave operation can be performed in various formats, the format selection in the interleave operation is performed by the encryption code, and the format selection of the deinterleave operation is performed by the decryption code. The secret story function is additionally achieved.

[0010]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 is a block circuit diagram showing the configuration of an embodiment of the magnetic disk device of the present invention. First, the recording data writing system will be described. Reference numeral 20 denotes a convolutional encoder, which includes three-stage shift registers 21, 22, 23 and two exclusive OR circuits 24, 25. The convolutional encoder 20 is an encoder having a coding rate of 1/2 for outputting 2-bit data with respect to 1-bit data input. Reference numeral 30 is an interleave operation circuit, and shift registers 31, 3
2, 37, 38 and M × M series (4 × 4 series in FIG. 2)
Matrix circuits 33 and 34 and matrix circuit 3
A plurality of conversion tables 35, 36, which are M × M series matrix circuits for storing the converted data of the data stored in 3, 34, and provided between the conversion tables 35, 36 and the shift registers 37, 38. Selectors 92 and 93 for selecting one of the conversion tables 35 and 36 according to the encryption code from the encryption key setting device 91. Four
1, 42 are write amplifiers, 43, 44 are media (disks)
It is a write head for D.

The data read system includes a read circuit 50 having heads 51 and 52, read amplifiers 53 and 54, and Viterbi equalizers 55 and 56, and shift registers 71, 72, 77 and 7.
8, M × M series matrix circuits 73 and 74, a plurality of conversion tables 75 and 76 which are M × M series matrix circuits for storing the converted data of the data stored in the matrix circuits 73 and 74, and Conversion table 7
Selectors 95 and 96 provided between the shift registers 77 and 78 and the shift registers 77 and 78 to select one of the conversion tables 75 and 76 by the decryption code from the decryption key setting device 94.
And a Viterbi decoder 80.

In this embodiment, the heads 43 and 44 for the number of symbols of the convolutional code and the interleave operation circuit 30 are used to record and reproduce simultaneously.
The transfer rate becomes faster. In this embodiment, the symbols of the convolutional code obtained by the convolutional encoder 20 are stored in the matrix circuits 33 and 34 via the shift registers 31 and 32 respectively for the M × M matrix, and the stored matrix is stored. Is converted in a plurality of predetermined conversion formats such as transposition, and the order of the time series is changed,
It is stored in a plurality of conversion tables 35 and 36 each having the same matrix. Then, after that, data is transferred from the one conversion table 35, 36 selected by the encryption code from the encryption key setting unit 91 to the shift register 3
4 bits are read by 7 and 38, and the disk D is read by the write amplifiers 41 and 42 and the write heads 43 and 44.
Recorded in.

FIG. 3 illustrates transposition, which is one of the above-mentioned conversion formats, by taking a 4 × 4 matrix circuit 33 as an example, and in order to facilitate understanding, input data is provided with numbers indicating the order. ing. As shown in (a), the data is first stored in the shift register 31 bit by bit, and when the data is stored in 4 bits, the matrix circuit 3
Moved to 3. The data stored in the matrix circuit 33 is shifted by 4 bits, and when 16 bits of data are stored in the matrix circuit 33, they are transposed as shown in (b). This transposition is an operation of transposing the rows and columns of the data stored in the matrix circuit 33, and the transposed data is transferred to the conversion table 35 which is another matrix circuit. Then, the transposed data is read from the matrix circuit 35 to which the data has been transferred by 4 bits by the shift register 37 (a selector is not shown in this description). The data read by the shift register 37 is interleaved data. At this time, the following data is input from the shift register 31 to the original matrix circuit 33 by 4 bits at a time.

On the other hand, the signals read from the read heads 51 and 52 are amplified by the read amplifiers 53 and 54, and the intersymbol interference is removed by the Viterbi equalizers 55 and 56. The outputs of the Viterbi equalizers 55 and 56 are output to the shift registers 71 and 7, respectively.
The M × M matrix is stored in the matrix circuits 73 and 74 via 2, and the matrix is transposed in the stored state to change the order of the time series and stored in the conversion tables 75 and 76 which are different matrix circuits. .. Then, after that, it is read from the conversion tables 75 and 76 by 4 bits by the shift registers 77 and 78 and returned to the original time series. After this, the shift registers 77, 78
The correct time-series convolutional code that is the output of is input to the Viterbi decoder 80 and is decoded.

Although the transposition has been described above, the rows and columns of the data stored in the matrix circuit 33 are exchanged according to a predetermined rule even in other conversion formats, and the data is another matrix circuit 1 of the conversion table 35. Transferred to one. The conversion of the data stored in the matrix circuit 33 by the conversion format including transposition is performed by the number of conversion tables 35 or the number of encryption codes (≦ the number of conversion tables).

In the deinterleave operation,
The data stored in the matrix circuits 73 and 74 is inversely converted using the same format as the plurality of conversion formats in the interleave operation, and the conversion table 3
The converted data are stored in the conversion tables 75 and 76 of the same number as 5 and 36, respectively. In this case, of the inversely converted data of the conversion tables 75 and 76, only one data is obtained by correct inverse conversion. After this, the selector 9 is selected by the decryption code from the decryption key setting circuit 94.
5, 96 selects the correctly converted one of the conversion tables 75, 76, and the data is selected in the shift register 7
The data is output to 7,78 for decoding.

By the above operation, even if errors occur continuously due to the erroneous judgments of the Viterbi equalizers 55 and 56 at the time of signal reproduction, the erroneous judgments are dispersed as M-interval errors by the deinterleaving operation, and the Viterbi decoder is decoded. The code input to 80 is a convolutional code close to a random error. In the interleave operation, the data is converted in a plurality of conversion formats, selected by one encryption code of the conversion format and written in the medium, and in reproduction, the reproduction signal is converted in the same number of conversion formats as in interleaving and the conversion table 75, Since the data is stored in 76, it is unknown which data in the conversion table is the data that has been correctly reverse-converted without the decryption code, and the confidential communication function is provided to a third party who does not know the decryption code.

In this way, in the above-described embodiment, the disadvantage of the convolutional code, which is weak against burst errors, is compensated for with the confidential function, the deterioration of the error correction capability of the Viterbi decoder 80 is minimized, and the data is There is less risk of eavesdropping. FIG. 4 shows the configuration of another embodiment of the magnetic disk device of the present invention. The same components as those of the magnetic disk device shown in FIG. 2 are designated by the same reference numerals.

The magnetic disk device of this embodiment differs from the magnetic disk device shown in FIG. 2 in that the clock frequency is doubled in FIG. 2 and the number of circuit components is reduced. That is, the shift registers 32 and 38 forming the interleave operation circuit 30 of FIG. 2, the M × M series matrix circuit 34, the conversion table 36, the selector 93,
The write amplifier 42 and the write head 44 are deleted from the write system, and the read amplifier 52 and the read head 5 from the read system.
4, Viterbi equalizer 56, deinterleave operation circuit 70
The shift registers 72 and 78, the M × M series matrix circuit 74, the conversion table 76, and the selector 96, which are included in FIG. Then, instead, a selector 26 is provided between the convolutional encoder 20 and the interleave operation circuit 30 ′ whose components are halved, and a selector 26 that selects data of either the exclusive OR circuits 24 and 25 is provided. A multiplexer 79 is inserted between the Viterbi decoder 80 and the de-interleave operation circuit 70 ′ whose components are halved.

In this embodiment, the convolutional code is selected by the selector 26.
The basic operation is the same as that of the magnetic disk device of the embodiment shown in FIG. 2 except that the read / write head, the interleave operation circuit, and the deinterleave operation circuit are reduced in size by switching the recording / reproducing mode. .. Therefore,
In this embodiment, conversion is performed by a plurality of conversion formats for each M × M data block in the writing system, the time series order is changed, and the data is stored in the plurality of conversion tables 35. In the read system, the head 51
The inter-code interference of the signal read from is removed by the Viterbi equalizer 55, inverse conversion is performed for each M × M data block by the same number of conversion formats as the interleave operation, and each data is stored in the conversion table 76. It Then, the data correctly inversely converted by the selector 96 is returned to the original time series. Further, it is returned to the convolutional code by the multiplexer 79 and is decoded by the Viterbi decoder 80.

FIG. 5 shows still another embodiment of the magnetic disk device of the present invention. In the magnetic disk device shown in FIG. 4, the conversion table corresponding to the encryption code and the decryption code is also used as a reversibility. Is shown in FIG.
The same reference numerals are given to the same constituent members as those in the embodiment. The magnetic disk device of this embodiment differs from the magnetic disk device shown in FIG. 4 in that the write system interleave operation circuit and the read system reverse interleave operation circuit are shared, and the number of circuit components is reduced. Is. For example, a case of eliminating the read system by leaving the write system interleave operation circuit will be described with reference to FIG.
Shift register 71, 78 constituting the inverse interleave operation circuit 70 ', and the matrix circuit 7 of M × M series
3, the conversion table 76, and the selector 96 are deleted. Instead, a selector 97 that selects either the selector 26 or the Viterbi equalizer 55 is provided in the preceding stage of the shift register 31, and either the write amplifier 41 or the multiplexer 79 is provided in the subsequent stage of the shift register 37. Is provided with a selector 98, which further selects the selector 9
There is provided a selector 99 for connecting 2 to either the encryption key setting device 91 or the decryption key setting device 92.

In this embodiment, the selector 26 is used for writing.
Of the output of the Viterbi equalizer 55 is connected to the shift register 31 by the selector 97, and the output of the Viterbi equalizer 55 is connected by the selector 97 at the time of reading. Shift register 37 to multiplexer 79
The basic operation is the same as that of the magnetic disk apparatus of the embodiment of FIG. 4 except that the interleave operation circuit and the de-interleave operation circuit are connected to each other to reduce the circuit scale.

Therefore, in this embodiment, M is used in the writing system.
Conversion is performed by a plurality of conversion formats for each of the × M data blocks, the time series order is changed, and the data is stored in the plurality of conversion tables 35. Further, in the reading system, the inter-code interference of the signal read from the head 51 is removed by the Viterbi equalizer 55, and inverse conversion is performed for each M × M data block by the same number of conversion formats as the interleave operation, and the conversion table Each data is stored in 35. Then, the data correctly inversely converted by the selector 92 is returned to the original time series, passed through the shift register 37 and the selector 98, returned to the convolutional code by the multiplexer 79, and decoded by the Viterbi decoder 80.

In this embodiment, the conversion table can be made small if the conversion format is reversible. That is, for example, when the format that changes from A to B is used for the interleave operation and the format that changes from B to A is used for the deinterleave operation, the format that changes from B to A is used for the interleave operation. If the format of changing to B is used for the deinterleave operation, one format can be used as two kinds of formats, and the conversion table is halved.

The embodiment of FIG. 6 is the same as the embodiment of FIG.
The random number table 100 is used as a data conversion format. In this embodiment, in order to spread the spectrum of the convolutional code and write it to the medium, the exclusive OR circuit 101 takes the exclusive OR of the data with the random number table 100 and scrambles the data.
In this embodiment, even if the recorded data is biased such that zeros continue, if the exclusive OR is taken with the random number table by scrambling, 1 is randomly inserted in the data actually written to the medium. As a result, a clock component appears in the read signal, and the PLL (Pha
The clock can be regenerated by the se Lock Loop) circuit.

As described above, according to the present invention, the recording data is once encoded by the convolutional code, and the secret code function by the encryption code is added when the data is written by using the interleave operation for changing the time series order of the code for each block. At the time of reading, the Viterbi equalized reproduction signal is restored to the correct time-series convolutional code by the deinterleaving operation by the deinterleaving operation and the decoding code, and the error correction decoding is performed by the Viterbi decoder or the sequential decoder. Even if the S / N ratio of the read signal becomes poor, erroneous determination in Viterbi equalization is less likely to occur, and the risk of wiretapping of data is eliminated.

Further, according to the present invention, a large coding gain is obtained by using a non-systematic code having a long constraint length as a convolutional code, and the recording density is increased by the coding gain without being intercepted by data. be able to.

[0028]

As described above, according to the present invention,
Encode the recorded data with a convolutional code, write it using an interleave operation that switches the time series order of the code for each block, and write the Viterbi equalized reproduction signal into a correct time series convolutional code by the deinterleave operation when reading. In a magnetic disk device that performs error correction decoding with a return and Viterbi decoder or a sequential decoder, by performing the confidential processing using interleaving processing and reverse interleaving processing that switch time series without using encryption and decryption programs Even if the S / N ratio of the read signal from the magnetic disk becomes poor, there is an effect that an erroneous determination in Viterbi equalization is unlikely to occur, and there is no fear that the confidential processing is performed and wiretapping is performed.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram showing a configuration of a magnetic disk device of the present invention.

FIG. 2 is a block circuit diagram showing a configuration of an embodiment of a magnetic disk device of the present invention.

FIG. 3A and FIG. 3B are both conversion formats of FIG.
It is explanatory drawing explaining the transposition which is one.

FIG. 4 is a block circuit diagram showing the configuration of another embodiment of the magnetic disk device of the present invention.

FIG. 5 is a block circuit diagram showing the configuration of still another embodiment of the magnetic disk device of the present invention.

FIG. 6 is a block circuit diagram showing a configuration of still another embodiment of the magnetic disk device of the present invention.

FIG. 7 is a block configuration diagram showing a configuration of a conventional magnetic recording / reproducing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Convolutional coding means 2 ... Interleave means 3 ... Cryptographic code input means 4 ... Write amplifier 5 ... Read amplifier 6 ... Deinterleaver means 7 ... Decoding code input means 8 ... Maximum likelihood decoding means 9 ... Record data switching means 9 , 10 ... Recording data switching means 24, 25, 101 ... Exclusive OR circuit 20 ... Convolutional encoders 21, 22, 23, 31, 32, 37, 38, 71, 7
2, 77, 78 ... Shift register 26, 92, 93, 95, 96, 98, 99 ... Selector 30, 30 '... Interleave operation circuit 33, 34, 73, 74 ... Matrix circuit 35, 36.75, 76 ... Conversion Table 41, 42 ... Write amplifier 43, 44 ... Write head 51, 52 ... Read head 53, 54 ... Read amplifier 55, 56 ... Viterbi equalizer 70, 70 '... Reverse interleave operation circuit 79 ... Multiplexer 80 ... Viterbi Decryptor 91 ... Encryption key setting device 94 ... Decryption key setting device 100 ... Random number table

Claims (5)

[Claims] 1. A magnetic disk device which reproduces data recorded on a magnetic disk (D) by a magnetic head (H) and decodes a reproduced signal by a maximum likelihood decoding method, wherein the recording data is convoluted at the time of recording. Convolutional coding means (1) for converting into a code, and interleaving means (2) capable of performing an interleaving operation corresponding to the channels of the symbols of the convolutional code in various formats on the convolutionally coded data. ), An encryption code input means (3) for inputting an encryption code for selecting a format in the interleave operation to the interleave means (2), and a head (H) prepared for the channel by amplifying the interleaved data. ), And a reproduction signal from the write amplifier (4) and the head (H) prepared for the channels. And a de-interleaving means (6) capable of performing a de-interleaving operation on the reproduction signal from the de-reading amplifier (5) in various formats and returning the reproduction signal to convolutionally encoded reproduction data. ), And a decoding code input means (7) for inputting a decoding code for selecting a format in the deinterleaving operation to the deinterleaving means (2), and the maximum likelihood decoding method for the convolutionally encoded reproduction data. Maximum likelihood decoding means for decoding while performing error correction (8)
A magnetic disk drive comprising: 2. A recording data switching means (9) for time-division of recording data existing for channels corresponding to the symbols of the convolutional code and transmitting the recording data to an interleaving means (2) for one channel, and the deinterleaving means. Multiplexer unit (10) for returning the reproduced signal from (6) to the convolutional code for the channel in time division in synchronization with the operation of the recording data switching unit (9), further comprising: The magnetic disk device according to claim 1. 3. The interleaving means (2) temporarily stores the convolutionally encoded data in a matrix, performs interleaving operations in a plurality of formats to store in a conversion table, and inputs the data from the cipher code input means (3). One of the conversion tables is selected by an encryption code to perform an interleaving operation, the deinterleaving means (6) temporarily stores the reproduced signal in a matrix, and the deinterleaving operation is performed in a plurality of formats to form a conversion table. 3. The magnetic disk drive according to claim 1, wherein the interleave operation is performed by storing one of the conversion tables according to a decoding code input from the decoding code input means (7). .. 4. The interleaving means (2) and the deinterleaving means (6) share a matrix for temporarily storing data and a conversion table, and a selector makes a connection in writing, a connection in reading mode, and an encryption code input. 3. The magnetic disk device according to claim 1, wherein the connection between the means (3) and the decoding code input means (7) is switched. 5. The format of the interleaving operation and the deinterleaving operation of the interleaving means (2) and the de-interleaving means (6) is performed by taking an exclusive OR using a random number table. 5. The magnetic disk device according to any one of 1 to 4.