JP3905230B2 - Magnetic disk drive and synchrobyte detection signal generation method used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk device for performing a process of reading data from a signal read by a magnetic head by generating a detection signal for a synchrobyte recorded at the previous position of the data, and a synchrobyte detection used in the magnetic disk device The present invention relates to a signal generation method, and in particular, a magnetic disk device capable of generating an accurate detection signal of a synchrobyte even when bit corruption occurs in a signal read by a magnetic head, and a synchrobyte used in the magnetic disk device The present invention relates to a detection signal generation method.
[0002]
[Prior art]
FIG. 11 shows an example of the track format of the magnetic disk.
As shown in FIG. 11A, SV (servo data) used for track positioning and user data (DATA 1 to DATA) composed of 512 bytes or the like are recorded on the track of the magnetic disk. .
[0003]
This SV is recorded radially at regular intervals with a number such as 80 on one circumference of the track. For example, as shown in FIG. 11B, the SV is recorded at the head, followed by the SV. Servo mark (SM) indicating that it is, followed by a Gray code for recording track information such as a track number, followed by a positional relationship as shown in FIG. 12 used for track positioning, etc. Has position marks (A to D in the figure).
[0004]
On the other hand, for example, as shown in FIG. 11C, the user data includes a preamble at the head, followed by a synchrobyte (SB) indicating the recording position of the user data, followed by the original user data, Following that, it has an EEC code, followed by a postamble.
[0005]
According to the track format having such a configuration, when the magnetic disk device detects the synchro byte when reading the SV and performing the track positioning, it extracts the user data by cutting out the byte data from the serial data read signal. The configuration of reading is adopted.
[0006]
In a conventional magnetic disk device, as a detection method of the synchrobyte, a signal having the same bit length as the synchrobyte is continuously extracted from the signal read by the magnetic head, and the distance between the extracted signal and the synchrobyte is determined. A method of calculating a synchrobyte detection signal by extracting and extracting a signal closest in distance as a synchrobyte has been adopted.
[0007]
[Problems to be solved by the invention]
However, according to such a conventional technique, there is a problem in that an accurate detection signal of a synchrobyte cannot be generated if a bit garbled signal is generated in the signal read by the magnetic head.
[0008]
In other words, when bit corruption occurs in the signal read by the magnetic head, there may be a plurality of signals having the same distance similar to the synchrobyte. In such a case, in the conventional technique, the signal found first is the synchrobyte. Therefore, there is a problem that an accurate detection signal for the synchrobyte cannot be generated.
[0009]
The present invention has been made in view of such circumstances, and provides a new magnetic disk device capable of generating an accurate detection signal of a synchrobyte even when bit corruption occurs in a signal read by a magnetic head. Another object of the present invention is to provide a new synchrobyte detection signal generation method used in the magnetic disk device.
[0010]
[Means for Solving the Problems]
FIG. 1 illustrates the principle configuration of the present invention.
In the figure, reference numeral 1 denotes a magnetic disk device including the present invention, which includes a magnetic disk 10, a magnetic head 11, and a magnetic disk controller 12, and reads data from the magnetic disk 10 or writes data to the magnetic disk 10. It is something to be drunk.
[0011]
The magnetic disk device 1 including the present invention generates a synchrobyte detection signal recorded at the previous position of data using the SB detection signal generation mechanism 13 to read data from a signal read by the magnetic head 11. The SB detection signal generation mechanism 13 includes a cutting means 14, a calculation means 15, an extraction means 16, and a generation means 17 in order to generate the synchrobyte detection signal.
[0012]
This cutting means 14 continuously cuts out a signal having the same bit length as the synchrobyte from the signal read by the magnetic head 11. The calculating means 15 calculates the distance between the signal cut out by the cutting means 14 and the synchrobyte.
[0013]
The extraction means 16 receives the distance set value as input, and extracts the signal position of the one similar to the synchrobyte from the signals extracted by the extraction means 14 according to the distance set value. The generation means 17 receives the order setting value and generates a synchrobyte detection signal from the signal position extracted by the extraction means 16 according to the order setting value.
[0014]
In the magnetic disk apparatus 1 having the present invention configured as described above, the extraction unit 16 inputs a distance setting value that is updated when data reading is not successful, and uses the distance setting value as a reference. By evaluating the distance calculated by the calculation means 15, the signal position similar to the synchrobyte is extracted from the signals extracted by the extraction means 14.
[0015]
Then, in response to the extraction process of the extraction unit 16, the generation unit 17 inputs the order setting value that is updated when the data reading is not successful, and the signal is extracted from the signal positions extracted by the extraction unit 16. By selecting the one indicated by the order setting value, a synchrobyte detection signal is generated.
[0016]
As described above, in the magnetic disk device 1 having the present invention, the order setting value is generated when the signal read by the magnetic head 11 is garbled and a plurality of signals similar to the synchrobytes are present. By using this, it is possible to generate a synchrobyte detection signal by making it possible to arbitrarily select a signal in the signal, so that an accurate synchrobyte detection signal can be generated.
[0017]
Further, in the magnetic disk device 1 of the present invention, when there are two synchrobytes recorded at the previous position of the data, the SB detection signal generation prepared for generating the detection signal of the synchrobyte recorded before is performed. The mechanism 13 and the SB detection signal generation mechanism 13 prepared for generating a synchrobyte detection signal to be recorded later are prepared, and the detection signal output from the former SB detection signal generation mechanism 13 is divided into two synchronization signals. The delay means for delaying by the time corresponding to the byte recording position, the detection signal output from the delay means, and the detection signal output from the latter SB detection signal generation mechanism 13 are input and output earlier. Detection of synchrobytes by providing a selection means for selecting and outputting one of the detection signals to be output or selecting and outputting one of them in accordance with a set selection instruction To generate the issue.
[0018]
According to this configuration, even when there are two synchrobytes recorded at the previous position of the data, it is possible to generate an accurate synchrobyte detection signal using the order setting value.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail according to embodiments.
FIG. 2 shows the configuration of the magnetic disk device 1 having the present invention. In the figure, the same components as those described in FIG. 1 are indicated by the same symbols.
[0020]
110 is a read head of the magnetic head 11 that reads data recorded on the magnetic disk 10, 111 is a write head of the magnetic head 11 that writes data to the magnetic disk 10, and 20 is It is a read channel and extracts user data (NRZ DATA) recorded on the magnetic disk 10 from a signal output from the read head 100.
[0021]
As shown in this figure, a read gate signal (generated in synchronization with detection of RG: SV), slice data, and counter data is given from the magnetic disk controller 12 to the read channel 20, and responds thereto. Then, user data (including ECC) and a read clock signal (READ CLK) are output from the read channel 20 to the magnetic disk controller 12.
[0022]
FIG. 3 illustrates one embodiment of a read channel 20 that implements the present invention.
The read channel 20 according to this embodiment includes an SB detection signal generator 21 that generates a synchrobyte detection signal included in a signal read by the read head 110, and a signal demodulator 22 that demodulates the signal read by the read head 110. And a data decoder 23 for extracting user data and ECC by cutting out byte data from a signal output from the signal demodulator 22 in synchronization with a synchro byte detection signal generated by the SB detection signal generator 21.
[0023]
The SB detection signal generator 21 includes a shift register 24 that has the same bit length as the synchrobyte and holds a signal read by the read head 110 while shifting the bit by bit, and an EOR circuit. The comparator 25 that compares the signal held by and the synchrobyte in a bit-corresponding manner and the number of bits detected by the comparator 25 as not matching are counted, so that the signal held by the shift register 24 and the synchrobyte The hamming distance calculator 26 for calculating the hamming distance between the hamming distance and the slice data output from the magnetic disk controller 12 is used as an input, and the hamming distance is equal to or smaller than the slice data among the signals output from the hamming distance calculator 26 A gate 27 that allows only the signal to pass through, and the output from the magnetic disk controller 12 As input Ntadeta, from the output signal of the gate 27, and a counter 28 for selecting and outputting a signal appearance order to specify the counter data as a detection signal of the sync byte.
[0024]
According to this configuration, the gate 27 passes three signals according to the slice data output from the magnetic disk controller 12, for example, as shown in (1) of FIG. 4, and the counter 28 outputs the magnetic disk controller 12. According to the slice data, for example, as shown in (2) of FIG. 4, the third signal output from the gate 27 is selected to operate so as to output a synchrobyte detection signal.
[0025]
In such a configuration, the magnetic disk controller 12 supplies slice data having a value of “0” to the gate 27 and counter data having a value of “1” in the counter 28 during normal operation. To give.
[0026]
In response to this, during normal operation, the Hamming distance calculator 26 calculates the Hamming distance “0” when the synchrobyte is held in the shift register 24, and from “0” otherwise. In response to this, the gate 27 passes the signal when the Hamming distance “0” is calculated, and the counter 28 indicates the first. When the hamming distance “0” is calculated according to “1” of the counter data, a synchrobyte detection signal is output.
[0027]
For example, when the read head 110 reads a signal as shown in (1) of FIG. 5, the comparator 25 follows the format shown in (2) of FIG. Compared with “00010110” and receiving this, the Hamming distance calculator 26, as shown in (3) and (4) in FIG. In addition to calculating “0”, a Hamming distance indicating a value larger than “0” is calculated at other times, and the gate 27 receives a signal when the Hamming distance “0” is calculated. In response to this, the counter 28 outputs a synchrobyte detection signal when the hamming distance “0” is calculated, as shown in (5) of FIG.
[0028]
In response to the detection signal of the synchrobyte, the data decoder 23 extracts user data and ECC from the signal output from the signal demodulator 22, so that the magnetic disk controller 12 uses the ECC extracted by the data decoder 23 to By evaluating the user data extracted by the decoder 23, it is determined whether or not the user data can be read from the magnetic disk 10.
[0029]
When it is determined that the user data cannot be read from the magnetic disk 10 according to this determination process, the magnetic disk controller 12 executes the process flow shown in FIGS. 6 and 7 to perform the user data read process according to the present invention. Execute.
[0030]
That is, when the magnetic disk controller 12 determines that the user data output from the data decoder 23 cannot be read, the magnetic disk controller 12 enters the execution of the processing flow of FIGS. 6 and 7 while performing positioning on the same track. First, in step 1, initial value “1” is set in variable S, initial value “1” is set in variable N, initial value “1” is set in variable i, and in step 2, the value of variable S is set as slice data. While giving to the gate 27, the value of the variable N is given to the counter 28 as counter data.
[0031]
In response to the setting of the slice data “1”, the gate 27 passes a signal when the Hamming distance “0” to “1” is calculated. Upon receiving the counter data “1”, the counter 28 By outputting the first signal from the signals output from the gate 27, a synchrobyte detection signal is output. Upon receiving this synchrobyte detection signal, the data decoder 23 performs processing for extracting user data and ECC by cutting out byte data from the signal output from the signal demodulator 22 in synchronization with the detection signal. .
[0032]
From now on, the magnetic disk controller 12 gives the value of the variable S to the gate 27 as slice data in step 2 and also gives the value of the variable N to the counter 28 as counter data. Subsequently, in step 3, the data decoder 23 Using the extracted ECC, the user data extracted by the data decoder 23 is evaluated to determine whether the user data can be read from the magnetic disk 10 or not.
[0033]
When it is determined that the user data can be read from the magnetic disk 10 according to this determination process, the process ends. When it is determined that the user data cannot be read, the process proceeds to step 4 where the value of the variable i is the specified maximum value. When it is determined whether or not (imax) has been exceeded, it is determined that the value has not been exceeded. In subsequent step 5, the value of variable i is incremented by one and then the process returns to step 2 to slice. The user data extraction process is retried without changing the data and counter data values.
[0034]
That is, when the user data cannot be read, the user data extraction process is retried up to a specified number of times without changing the values of the slice data and the counter data.
[0035]
On the other hand, when it is determined in step 4 that the value of the variable i has exceeded the prescribed maximum value, the process proceeds to step 6 where the initial value “1” is set in the variable i, and then in the subsequent step 7, When it is determined whether or not the value of the variable N exceeds the maximum number (Nmax) of the signals passing through the gate 27, and when it is determined that the value does not exceed, the value of the variable N is set to one in the following step 8. By returning to step 2 after incrementing, only the value of the counter data is incremented by one without changing the value of the slice data, and the user data extraction process is retried.
[0036]
That is, when the slice data is fixed and the first signal among the signals output from the gate 27 is output as the synchrobyte detection signal a predetermined number of times, and the user data cannot be read out yet, the gate data If the second signal among the signals output from the terminal 27 is output as a synchrobyte detection signal a predetermined number of times, and the user data cannot be read out yet, the third signal among the signals output from the gate 27 is output. The user data extraction process is retried by performing the specified number of times of outputting the second signal as a synchrobyte detection signal.
[0037]
On the other hand, when it is determined in step 7 that the value of the variable N has exceeded the maximum number of signals passing through the gate 27, the process proceeds to step 9 (processing flow of FIG. 7), and the variables N and i are initialized. After the value “1” is set, in the following step 10, it is determined whether or not the value of the variable S exceeds the specified maximum value (Smax). 11, the value of the variable S is incremented by one and then the process returns to step 2, whereby the value of the slice data is incremented by one and the user data extraction process is retried.
[0038]
That is, at first, when the gate 27 passes the signal of the Hamming distance “0” to “1”, the user data extraction process is retried in the above-described format, and if the user data cannot be read yet, the Hamming distance “ If the user data extraction process is retried in the above-mentioned format while the signals 0 "to" 2 "are passed and the user data cannot be read out yet, the signals of the Hamming distances" 0 "to" 3 "are passed. However, the user data extraction process is retried in the above-described format.
[0039]
When it is determined in step 10 that the value of the variable S has exceeded the prescribed maximum value, the process proceeds to step 12 to notify the host device that the user data cannot be read. To end the process.
[0040]
In this way, in the magnetic disk apparatus 1 having the present invention, when the signal shown in (1) in FIG. 5 is read as a signal shown in (1) in FIG. 26, as shown in (3) and (4) of FIG. 8, the Hamming distance “2” is calculated at four time points including when the synchrobyte is held in the shift register 24, and at other times. , The Hamming distance showing a value larger than “2” is calculated, and the magnetic disk controller 12 outputs the second time when the Hamming distance “2” is calculated by executing the above-mentioned retry. Thus, the user data can be read from the magnetic disk 10 by extracting the synchrobyte detection signal as a normal detection signal.
[0041]
On the other hand, according to the conventional technology, since only the synchrobyte detection signal output at the time when the Hamming distance “2” is calculated first is effective, the magnetic field is adopted. The user data cannot be read from the disk 10.
[0042]
In addition to the user data having the data structure shown in FIG. 11C, as shown in FIG. 9, there are two synchrobytes such as a synchrobyte located at the front stage and a synchrobyte located at the rear stage. There is something.
[0043]
When handling user data having such a data structure, the read channel 20 comprises the SB detection signal generator 21 shown in FIG. 3 as shown in FIG. The second SB detection signal generator 21a and the SB detection signal generator 21 shown in FIG. 3 generate a synchrobyte detection signal located at the subsequent stage. 21b, the detection signal output from the first SB detection signal generator 21a, a delay unit 30 that delays the detection signal by the time corresponding to the recording positions of the two synchrobytes, the detection signal output from the delay unit 30, and the second The detection signal output from the SB detection signal generator 21b is input, and the detection signal output earlier is selected and output, or the selection instruction signal of the magnetic disk controller 12 is selected. I, a configuration and a selector 31 for outputting a detection signal of the synchronous byte by selecting and outputting either one of them.
[0044]
Even when this configuration is followed, the magnetic disk controller 12 still provides the slice data A / counter data A given to the first SB detection signal generator 21a and the slice data B / counter data given to the second SB detection signal generator 21b. By changing B, an accurate synchrobyte detection signal can be generated, so that user data can be read from the magnetic disk 10.
[0045]
【The invention's effect】
As described above, in the magnetic disk apparatus of the present invention, the order set value is used when a bit read error occurs in the signal read by the magnetic head and there are a plurality of signals similar to the synchrobyte. Thus, by adopting a configuration in which a synchrobyte detection signal is generated by making it possible to arbitrarily select a signal in the signal, an accurate synchrobyte detection signal can be generated.
[Brief description of the drawings]
FIG. 1 is a principle configuration diagram of the present invention.
FIG. 2 is a device configuration diagram of a magnetic disk device.
FIG. 3 is an example of a read channel.
FIG. 4 is a process explanatory diagram of an SB detection signal generator.
FIG. 5 is an operation explanatory diagram of the embodiment.
FIG. 6 is a processing flow executed by the magnetic disk controller.
FIG. 7 is a processing flow executed by the magnetic disk controller.
FIG. 8 is an operation explanatory diagram of the embodiment.
FIG. 9 is an explanatory diagram of a track format.
FIG. 10 is an example of a read channel.
FIG. 11 is an explanatory diagram of a track format.
FIG. 12 is an explanatory diagram of a track format.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Magnetic disk apparatus 10 Magnetic disk 11 Magnetic head 12 Magnetic disk controller 13 SB detection signal production | generation mechanism 14 Cutting means 15 Calculation means 16 Extraction means 17 Generation means

Claims (4)

In a magnetic disk device that performs a process of reading data from a signal read by a magnetic head by generating a detection signal for a synchrobyte recorded at the previous position of the data,
Cutting means for continuously cutting out a signal having the same bit length as the synchrobyte from the signal read by the magnetic head;
A calculation means for calculating a distance between a signal cut out by the cutting means and the synchrobite;
Extraction that extracts the signal position of the one similar to the synchrobyte from the signals extracted by the extraction means by evaluating the distance calculated by the calculation means with the distance set value as an input and evaluating the distance set value as a reference Means,
Including an order setting value as input, and generating means for generating a detection signal of a synchrobyte by selecting what the order setting value indicates from signal positions extracted by the extraction means.
A magnetic disk device. In a method for generating a synchrobyte detection signal used in a magnetic disk device that performs a process of reading data from a signal read by a magnetic head by generating a detection signal for a synchrobyte recorded at the previous position of data,
From the signal read by the magnetic head, a signal having the same bit length as the synchrobyte is continuously cut out, the distance between the cut out signal and the synchrobyte is calculated, and the distance setting value inputted is used as a reference, By evaluating the calculated distance, the signal position of the one similar to the synchrobyte is extracted from the extracted signal, and the one indicated by the input order setting value is selected from the extracted signal positions To generate a synchrobyte detection signal,
A method for generating a synchrobyte detection signal. In a magnetic disk device that performs a process of reading data from a signal read by a magnetic head by generating a detection signal of two synchrobytes recorded at the previous position of data,
Prepared for generating the synchrobyte detection signal recorded before, a signal having the same bit length as the synchrobyte is continuously extracted from the signal read by the magnetic head, and the extracted signal and the synchrobyte The signal position of the one similar to the synchrobyte is extracted from the cut out signal by evaluating the calculated distance with reference to the input distance setting value. A first generation means for generating a detection signal of a synchrobyte previously recorded by selecting one of the extracted signal positions indicated by the input order setting value;
Delay means for delaying the detection signal output from the first generation means by a time corresponding to the recording positions of the two synchrobytes;
A second generation means prepared for generating a synchrobyte detection signal to be recorded later, and generating a synchrobyte detection signal to be recorded later according to the same configuration as the first generation means;
A selection means for selecting and outputting a detection signal output earlier among the detection signal output from the delay means and the detection signal output from the second generation means;
A magnetic disk device. A magnetic disk device that performs processing of reading data from a signal read by a magnetic head by generating a detection signal of two synchrobytes recorded at a previous position of data,
Prepared for generating the synchrobyte detection signal recorded before, a signal having the same bit length as the synchrobyte is continuously extracted from the signal read by the magnetic head, and the extracted signal and the synchrobyte The signal position of the one similar to the synchrobyte is extracted from the cut out signal by evaluating the calculated distance with reference to the input distance setting value. A first generation means for generating a detection signal of a synchrobyte previously recorded by selecting one of the extracted signal positions indicated by the input order setting value;
Delay means for delaying the detection signal output from the first generation means by a time corresponding to the recording positions of the two synchrobytes;
A second generation means prepared for generating a synchrobyte detection signal to be recorded later, and generating a synchrobyte detection signal to be recorded later according to the same configuration as the first generation means;
A selection unit configured to select the detection signal output from the delay unit and the detection signal output from the second generation unit as input and select and output one of them according to a set selection instruction; That
A magnetic disk device.

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