JP4173931B2 - Magnetic disk drive and data reading method used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk device that performs a process of reading data from a signal read by a magnetic head by artificially generating a synchrobyte detection signal recorded at the previous position of data when thermal asperity occurs In particular, the present invention relates to a data reading method used in the magnetic disk device, and more particularly, to a magnetic disk device that enables high-speed data reading and a data reading method used in the magnetic disk device.
[0002]
[Prior art]
FIG. 6 shows an example of the track format of the magnetic disk.
As shown in FIG. 6A, 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 in a radial manner with a number such as 80 on one circumference of the track. For example, as shown in FIG. 6 (b), 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. 7 used for track positioning, etc. Has position marks (A to D in the figure).
[0004]
On the other hand, the user data is, for example, as shown in FIG. 6C, 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]
On the other hand, recent magnetic disk devices use MR heads composed of magnetoresistive elements because of their small size and high sensitivity.
In this magnetic disk apparatus using the MR head, when the MR head collides with or comes into contact with only a few protrusions on the surface of the rotating magnetic disk, the thermal asperity in which the temperature of the MR head rapidly increases due to frictional heat. A phenomenon called (TA) occurs.
[0007]
When this thermal asperity occurs, the resistance value of the magnetoresistive element changes depending on the temperature, thereby shifting the base line of the signal read by the MR head, making it impossible to read user data.
[0008]
Therefore, in the conventional magnetic disk device, when the occurrence of thermal asperity in the synchrobyte area is detected because the user data cannot be read, as shown in FIG. 8, the rise of the read gate signal (RG) is used as a reference. When a set time (set by counting the clock using a counter) elapses, a pseudo synchrobyte detection signal (FORCE SB) is forcibly generated.
[0009]
Then, in synchronization with this pseudo sync byte detection signal, the byte data is cut out from the serial data read signal, and whether or not the user data can be read out using the ECC is read out. When it is determined that there is no data, the user data is read by sequentially changing the set time (changing the set value of the counter) on the same track.
[0010]
Here, the read gate signal is generated in synchronization with the detection of servo data.However, since it is byte clock synchronous, a byte-by-byte position shift occurs, or in the case of a synchro byte far from the servo data position. Depending on the rotational fluctuation of the spindle motor, the rise of the synchrobite and read gate signal on the medium may fluctuate greatly.
[0011]
[Problems to be solved by the invention]
Thus, in the conventional magnetic disk device, when the occurrence of thermal asperity in the synchrobyte area is detected because the user data cannot be read, when the set time with respect to the rise of the read gate signal elapses, A configuration is adopted in which user data is read from a signal read by the magnetic head by generating a pseudo synchrobyte detection signal by trial and error.
[0012]
However, according to such a conventional technique, there is a problem that user data cannot be read at high speed when thermal asperity occurs.
That is, the rise of the read gate signal is not directly synchronized with the protrusion on the surface of the magnetic disk that causes thermal asperity. That is, the rise of the read gate signal varies with respect to the synchrobyte position on the medium. Thus, according to the prior art, there is a problem in that user data cannot be read at high speed due to an increase in the number of trial and error.
[0013]
The present invention has been made in view of such circumstances, and adopts a configuration in which data is read from a signal read by a magnetic head by artificially generating a synchrobyte detection signal when thermal asperity occurs. In some cases, an object is to provide a new magnetic disk device that can read data at high speed and to provide a new data reading method used in the magnetic disk device.
[0014]
[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.
[0015]
The magnetic disk apparatus 1 having the present invention generates data from a signal read by the magnetic head 11 by artificially generating a synchrobyte detection signal recorded at the previous position of data when thermal asperity occurs. A reading process is performed, and in order to realize this process, a detection unit 13, a generation unit 14, and an extraction unit 15 are provided.
[0016]
The detection means 13 detects the occurrence of thermal asperity by monitoring the level of the signal read by the magnetic head 11. The generation unit 14 receives a set value set by the magnetic disk controller 12 and performs a clock counting process to generate a pseudo synchrobyte detection signal. The extracting unit 15 extracts data from the signal read by the magnetic head 11 using the detection signal generated by the generating unit 14.
[0017]
In the magnetic disk device 1 having the present invention configured as described above, the generation unit 14 receives the set value updated by the magnetic disk controller 12 when the data reading is not successful, and the detection unit 13 detects the thermal value. The counting of the clock is started from the point of time when the occurrence of asperity is detected, and when the count value reaches the set value, a pseudo synchrobyte detection signal is generated, and in response to this, the extracting means 15 Using the detection signal generated by the generation unit 14, data is extracted from the signal read by the magnetic head 11.
Upon receiving this data extraction, the magnetic disk controller 12 evaluates the extracted data to determine whether or not the data can be read from the magnetic disk 10 and cannot read the data from the magnetic disk 10. If it is determined, the setting value is updated and given to the generation unit 14 to instruct to regenerate the pseudo synchrobyte detection signal on the same track.
[0018]
As described above, the magnetic disk device 1 according to the present invention employs a configuration in which, when thermal asperity occurs, data is read from a signal read by the magnetic head by artificially generating a synchrobyte detection signal. Occasionally, when the set time with respect to the location where the thermal asperity occurs has elapsed, the data is read by generating a pseudo synchrobyte detection signal in a trial and error manner. The data can be read out with a much smaller number of trials than in the conventional technique based on the rising of the changing read gate.
[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 (RG) and a serial port signal are given from the magnetic disk controller 12 to the read channel 20, and in response to this, the read channel 20 sends to the magnetic disk controller 12. Thus, user data (including ECC) and a read clock signal (READ CLK) are output.
[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 a TA detector 21 that detects the occurrence of thermal asperity by monitoring the level of a signal read by the read head 110, a register 22 that holds a setting value notified by a serial port signal, When enabled by a read gate signal (generated in synchronization with detection of SV), the TA detector 21 starts counting clocks when detecting the occurrence of thermal asperity, and the count value is held in the register 22 The counter 23 that stops counting when it reaches the set value, the SB detection signal generator 24 that generates a pseudo synchrobyte detection signal when the counter 23 stops counting, and the reading head 110 reads The signal demodulator 25 that demodulates the signal and the pseudo thin output from the SB detection signal generator 24 In synchronization with the detection signal of kilobytes, and a data decoder 26 which extracts the user data and the ECC by cutting the byte data from the signal output of the signal demodulator 25.
[0023]
Here, although omitted in FIG. 3, a SB detection signal generator (thermal asperity is generated by detecting a synchrobyte included in a signal read by the read head 110 to generate a normal synchrobyte detection signal. If the thermal asperity is not generated, the data decoder 26 synchronizes with the normal synchrobyte detection signal generated by the SB detection signal generator. The user data and the ECC are extracted by cutting out the byte data from the signal output from the signal demodulator 25.
[0024]
FIG. 4 illustrates an example of a processing flow of the magnetic disk controller 12 that reads user data by controlling the read channel 20 configured as described above.
[0025]
Next, according to this processing flow, the operation processing of the embodiment configured as described above will be described in detail.
When the magnetic disk controller 12 determines that the user data output from the data decoder 26 cannot be read due to the occurrence of thermal asperity, the magnetic disk controller 12 starts the processing flow of FIG. 4 while performing positioning on the same track. First, in step 1, the initial value “n” is set in the variable N, and the initial value “1” is set in the variable i. In the subsequent step 2, the variable N is stored in the register 22 of the read channel 20. Set the value.
[0026]
In response to the setting of the variable value N for the register 22, the counter 23 of the read channel 20 starts counting the clock when the TA detector 21 detects the occurrence of thermal asperity, and the count value is held in the register 22. The SB detection signal generator 24 generates a pseudo synchrobyte detection signal when the count is stopped, and receives the data. The decoder 26 performs processing for extracting user data and ECC by cutting out byte data from a signal output from the signal demodulator 25 in synchronization with the pseudo synchrobyte detection signal.
[0027]
From now on, the magnetic disk controller 12 sets the value of the variable N in the register 22 of the read channel 20 in step 2, and subsequently, in step 3, the extraction of the data decoder 26 is performed using the ECC extracted by the data decoder 26. By evaluating the user data, it is determined whether or not the user data can be read from the magnetic disk 10.
[0028]
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, and it is determined that the value has not been exceeded, the value of the variable i is incremented by 1 in step 5 and the process returns to step 2 so that the register The user data extraction process is retried without changing the value set to 22.
[0029]
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 has exceeded the prescribed maximum value (Nmax), and not, it is determined that the value of the variable N is incremented by one in step 9 and then step is performed. By returning to 2, the value set in the register 22 is incremented by 1, and the user data extraction process is retried.
[0030]
If it is determined in step 7 that the value of the variable N has exceeded the specified maximum value, the process proceeds to step 8 to notify the host device that the user data cannot be read. To end the process.
[0031]
In this way, in the magnetic disk device 1 having the present invention, as shown in the time chart of FIG. 5, when a set time with respect to the location where the thermal asperity occurs is detected, a pseudo synchrobyte is detected. By generating a signal on a trial and error basis, the user data is read out.
[0032]
Here, the signal {circle around (1)} shown in FIG. 5 is the output signal of the TA detector 21, the signal {circle around (2)} is the output signal of the counter 23 (the signal that goes high when the counting process is stopped), and {circle around (3)}. The signal (4) is the output signal of the SB detection signal generator 24, and the signal (4) is the output signal of the signal demodulator 25. Further, clock deviation due to byte alignment occurs in the * portion of the read clock signal (READ CLK).
[0033]
【The invention's effect】
As described above, in the magnetic disk device of the present invention, when a thermal asperity occurs, the data is read from the signal read by the magnetic head by artificially generating a synchrobyte detection signal. Then, when the set time with respect to the occurrence location of thermal asperity elapses, the data is read out by trial and error generation of a pseudo synchrobyte detection signal. Data can be read out with a much smaller number of trials than in the prior art based on the rise of the changing read gate.
[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 processing flow executed by the magnetic disk controller.
FIG. 5 is a time chart of the embodiment.
FIG. 6 is an explanatory diagram of a track format.
FIG. 7 is an explanatory diagram of a track format.
FIG. 8 is an explanatory diagram of the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Magnetic disk apparatus 10 Magnetic disk 11 Magnetic head 12 Magnetic disk controller 13 Detection means 14 Generation means 15 Extraction means

Claims (2)

In a magnetic disk device that performs a process of reading data from a signal read by a magnetic head by artificially generating a synchrobyte detection signal recorded at the previous position of data when thermal asperity occurs,
Detecting means for detecting the occurrence of thermal asperity by monitoring the level of the signal read by the magnetic head;
The set value as an input, and starts counting the clock from the time when said detecting means detects the occurrence of a thermal asperity, when its count value reaches to the set value, generating a detection signal of the pseudo-sync bytes Generating means for
Using the detection signal generated by the generating means, extracting means for extracting data from the signal read by the magnetic head ;
A judging means for judging whether or not the data can be read from the magnetic disk by evaluating the data extracted by the extracting means;
Execution instructing to regenerate the pseudo synchrobyte detection signal on the same track when the determination means determines that data could not be read from the magnetic disk. Providing means,
A magnetic disk device. Data reading used in magnetic disk drives that perform processing to read data from signals read by the magnetic head by generating pseudo-detection signals for synchrobytes recorded at the previous position of data when thermal asperity occurs In the method
The process of detecting the occurrence of thermal asperity by monitoring the level of the signal read by the magnetic head ,
The set value as an input, and starts counting the clock from the time of detecting the occurrence of service over Mar asperity, when its count value has reached its set value, the process of generating a detection signal of the pseudo-sync bytes When,
Using the raw form sensing signals, and the process of extracting data from the signal reading of the magnetic head,
A process of judging whether or not the data can be read from the magnetic disk by evaluating the extracted data;
A step of instructing to regenerate the pseudo synchrobyte detection signal on the same track by updating the set value when it is determined that data could not be read from the magnetic disk. The
A data reading method used in a magnetic disk device.

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