JP2000242907A - Method and device for reading out information - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence of an unrecoverable error by repeating plural times of read-out operation related to a section that the data read out from an information recording medium aren't discriminated, operating plural data obtained respectively by plural times of read-out operation, reducing a noise component excepting a signal to be read out and trying the data discrimination. SOLUTION: A first time read-in signal V1 (t) 51 of a prescribed section not to be discriminated on a magnetic tape becomes S(t)+N1 (t) as the sum of the signal S(t) to be read out and the noise component N1 (t). Similarly, an n-th time read-in signal Vn (t) 53 of the same section becomes S(t)+Nn(t). The operation processing 54 makes coincide the time bases of the signals V1(t)...Vn(t) with each other to add them, and divides it by the number of times (n) to obtain S(t)+Σ(n=1...n)Nn (t)/n as an output 55. By the operation processing 54, only the noise component is reduced while making the size of the amplitude of the signal S (t) to be read out as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reading method and an information reproducing apparatus, and more particularly, to an information reading method and an information reproducing apparatus in which a data retry operation is performed a plurality of times at a place where data discrimination could not be performed to attempt data discrimination. About.

[0002]

2. Description of the Related Art For example, in an information reproducing apparatus such as a magnetic tape device, when reading data from an information storage medium,
A technique has been used in which a medium is driven at a speed several times to several tens of times the standard reproduction speed to read data, and the data transfer rate is improved accordingly to speed up the processing. However, in such high-speed driving, when external noise generated during reproduction is large, or when data is read from a medium of poor quality or a medium of poor quality due to scratches or dirt, the amount of correction error exceeding the correction limit May cause a read error.

[0003] In order to prevent the occurrence of such an unreadable error, various retry methods have been conventionally proposed. For example, in a magnetic tape device disclosed in Japanese Patent Application Laid-Open No. 06-131826, a reproduction signal processing circuit that receives an information signal read from a magnetic tape medium by a reproduction head reads error information when an uncorrectable read error occurs. Output to controller. The system controller having received the error information sends a retry command to the movable head controller. According to this command, the movable head control signal is output to the reproducing head displacement element, the reproducing head is displaced along the rotation axis, and the information track in which the error has occurred is scanned again. This retry operation is repeated until there is no error, and the magnetic tape is run at a low speed or stopped during this repetition operation. In this manner, the read head is displaced to attempt read retry, thereby reducing the occurrence of an unreadable error.

In a magnetic tape device disclosed in Japanese Patent Application Laid-Open No. 05-210815, when a data reading error occurs during a reproducing operation while a magnetic tape is running at a normal running speed, a specified number of readings is performed. If the retry operation is performed and the data cannot be reproduced correctly, the running speed of the magnetic tape is reduced to, for example, 1/3, and the re-read operation is performed. By reducing the traveling speed, the reproducing heads RA, R
In some cases, it is possible to scan even tracks B that could not be accurately scanned. By performing this operation, the reliability and reliability of data are improved.

[0005]

As described above, in the conventional magnetic recording / reproducing apparatus, the recovery cannot be performed by performing the read retry by displacing the reproducing head or by accurately scanning the head by reducing the tape speed. This prevents possible reading errors. However, even with the retry method as described above, when the reproduction output is too small to discriminate the data, or when the external noise generated at the time of reading is large, the data cannot be discriminated from the noise, and the data cannot be recovered. An error may occur.

Accordingly, the present invention provides an information reading method and an information reproducing apparatus for easily determining data and noise in a section where such a data reading error has occurred, thereby reducing the occurrence of an unrecoverable error. Aim.

[0007]

In order to achieve the above object, an information reading method according to a first aspect of the present invention is characterized in that when the data read from the information storage medium cannot be determined by the information reading means, the data determination is performed. In an information reading method in which data reading is repeated a plurality of times for a section where data cannot be read and data determination is attempted, a plurality of data obtained in each of the plurality of reading operations are calculated to obtain noise other than a signal intended for reading. Data discrimination is attempted by reducing components.

As described above, according to the present invention, a target signal can be extracted by calculation if there is a plurality of read data in the same section, even if a noise component and a target signal cannot be discriminated from one read data. By paying attention to the case, a plurality of read data for the same section obtained by repeating the read retry operation are calculated to reduce noise components, thereby improving the data discrimination achievement rate.

In the calculation, after adding the voltage levels on the same time axis for a plurality of data in the same section read in the plurality of reading operations, the reading operation is performed for the section in which the data could not be determined. It is characterized in that the voltage level for each time axis is divided by the number of times the operation is performed.
By performing such an operation, since the target signal is the same frequency component and the same phase for all read data in the same section, it remains as it is even if it is added and divided by the number of read times, while the noise component is the average. To be reduced.
By appropriately reducing only the noise component in this manner, data discrimination can be facilitated.

In the information reading method according to a third aspect of the present invention, data discrimination is attempted for one or both of the data obtained by performing the operation and the data obtained by the latest reading operation for the section. It is characterized by. If the noise component or S / N ratio does not change much even after repeated reading retries, the data obtained by performing the operation has higher discriminability than the read data, but the noise component is attenuated each time the repeated reading retries are repeated. Alternatively, when the S / N ratio is improved, the latest read data may have higher discrimination than the data obtained by performing the above calculation. For example, if an attempt is made to discriminate both data at each retry, it is possible to discriminate data in a better state, and it is possible to quickly avoid an unrecoverable error.

In the information reading method according to a fourth aspect of the present invention, the cleaning of the information reading means is automatically performed when the number of reading operations to the section where the data cannot be determined reaches a first predetermined number. It is characterized in that it is executed dynamically. If the data cannot be determined even after performing the read retry several times as described above, if the automatic cleaning is performed, the probability that the data can be determined in the subsequent retry operation increases, and the recovery is more preferably performed. Impossible errors can be avoided.

Further, in the information reading method according to the present invention, when the number of times of the reading operation to the section where the data cannot be determined reaches a predetermined second number, a cleaning request is issued to an operator or a host device. It is characterized by putting out. If the data cannot be determined even after performing the read retry several times, a cleaning request is issued to the outside and appropriate measures are taken to increase the probability that the data can be determined in the subsequent retry operation. Become
More preferably, an unrecoverable error can be avoided.

In the information reading method according to the present invention, when the number of read operations for the section where the data cannot be determined reaches a predetermined third number, it is determined that the data cannot be determined. Error processing is performed.
If data cannot be determined even after performing a predetermined number of retries, data in this section is determined to be unreadable and error processing is performed, so that excessive retry is avoided to prolong the interruption of processing. Is desirable.

Further, a division reproducing apparatus to which such an information reading method is applied is a medium driving means for driving an information storage medium, a signal reading means for reading data from the storage medium, and a data read by the information reading means. A data discriminating means for discriminating the data and a control means for controlling the operation of the apparatus, and when it is not possible to discriminate the data read from the information storage medium, a plurality of reading operations are performed for the section where the data discrimination could not be performed. An information reproducing apparatus that attempts data determination by repeating the above, further comprising a memory means for storing a plurality of data obtained by a plurality of read operations for a section where the data could not be determined; and A calculation processing method for calculating a plurality of read data in a section where no data exists and reducing only a noise component of data in the section. Characterized in that it comprises and.

[0015]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG.
1 is a block diagram showing a configuration of a magnetic tape device according to an embodiment of the present invention. As shown in FIG. 1, the magnetic tape device 1 includes at least a magnetic tape device main body 10 and a reproduction signal calculation unit 20.

The magnetic tape device main body 10 includes a tape deck mechanism 11, a recording / reproducing head 12, a head cleaning mechanism 13, a recording / reproducing circuit 14, an error correction circuit 15, a recording / reproducing control section 16, a display section. 17 are provided. The magnetic tape device main body 10 executes a recording / reproducing operation on a magnetic tape medium based on a command from a host device.

At the time of data writing, write data supplied from a higher-level device is added with an error correction code or the like by a recording / reproducing circuit 14 and is written on a magnetic tape via a recording / reproducing head 12. At the time of data reading, a signal read by the recording / reproducing head 12 is subjected to error correction based on an error correction code or the like by an error correction circuit 15, and the recording / reproducing circuit 14 determines whether or not the data can be determined. If the read data cannot be determined, the recording / reproduction control unit 16 drives the tape deck mechanism 11 to rewind the magnetic tape, and the reading process (read retry) is performed again.

The signal read by the recording / reproducing head 12 is also sent to a reproduced signal arithmetic processing unit 20. The reproduction signal arithmetic processing unit 20 includes an A / D conversion unit 21 and a memory A2.
2, a memory B23, an addition processing unit 24, a division processing unit 25, and a D / A conversion unit 26. When the magnetic tape device main body 10 performs a read retry operation, the read data is stored. Then, an operation for reducing noise in the section where the data cannot be determined is performed.

The operation of the magnetic tape device 1 configured as described above when reading data will be described below with reference to FIGS. As shown in FIG. 2, when the magnetic tape device receives a data read command from a host device, the magnetic tape device main body 10 is driven to perform a magnetic tape reading process (step 201). That is, a signal in a specific section on the tape according to a request from a higher-level device is read out by the recording / reproducing head 12, amplified by an amplifier circuit, passed through a target frequency band by a filter circuit, and fixed by an AGC (automatic gain) circuit. And the amplitude of Note that the amplification, filter, AG
The order in which the signals are passed through the C circuit is not limited to this, and it is not particularly necessary to pass all the signals.

The signal processed as described above is supplied to the data discriminating section (step 202) and the reproduced signal arithmetic processing section 2 at the same time.
0 (step 204). The data discriminator (step 202) discriminates the data of the received signal.
If the data can be determined, it is determined that the reading of the section has been completed normally, and the process proceeds to the next processing (step 203). If the data cannot be determined, the process branches to a retry process (steps 205 to 208) described later, and the data is read. The section is read again (return to step 201).

FIGS. 3 and 4 show the reproduction signal arithmetic processing unit 20.
It is a figure explaining the processing of. Referring to FIG. 3, the signal read in step 201 is first processed by A in the arithmetic processing unit 20.
It is converted into a digital code by the / D conversion unit 21. The digital code shown here is obtained by coding a voltage level sampled at a constant time interval.

This digital code is then stored in the memory A22. Upon receiving the new digital code, the memory A22 clears the previously stored digital code and saves a new signal as needed. The digital code stored here is then added by the addition processing unit 24 to the digital code related to data of the same section already obtained in the reading and stored in the memory B23. The term "addition" as used herein refers to the addition of voltage levels on the same time axis. The output of the addition processing unit 24 is
Is supplied to the memory B23. When receiving the new digital code, the memory B23 clears the previously stored digital code and newly stores the received digital code.

The division processing section 25 divides the digital code output from the addition processing section 24 by the number of times of reading in the section. Here, division refers to dividing the voltage level for each time axis by the number of times read. The divided digital code is converted into an analog signal by the D / A converter 26 and output to the data discriminator (step 202), and data discrimination is attempted. When receiving the reset signal 1, the reproduction signal arithmetic processing section 20 clears all data in the memories A22 and B23.

FIG. 4 is a diagram for explaining the operation of the reproduction signal operation processing section 20 for reducing only the noise component by using a plurality of read data for the same section. As described above, when the read data cannot be determined, the read retry operation in the section where the read data cannot be determined is repeated. All the read signals obtained in each retry operation are supplied to the reproduction signal operation processing unit 20 and are operated each time.
Here, when a signal V1 (t) obtained by reading a specific section on the magnetic tape for the first time is represented by a time function, a target signal S (t) is obtained.
And S (t) + N1 as the sum of noise component N1 (t)
(T) (51). Similarly, the signal V2 (t) that has read the same section for the second time is S (t) + N2 (t) (52), and the signal Vn (t) that has been read for the nth time is S (t).
(T) + Nn (t) (53).

In the arithmetic processing section 20, these signals are added and divided by the number of readings (processing 54: Σ (n = 1
To n) Nn (t) / n). In other words, when the time axes of the first to n-th signals are made coincident with each other and added, and the magnitude of the amplitude is divided by the number n of times of reading, the arithmetic processing unit 20
Is S (t) + Σ (n = 1 to n) Nn (t) / n
(55).

Since the target signal S (t) has the same frequency component and the same phase in each read signal, the target signal S (t) can be obtained by multiplying the target signal S (t) by multiplying the read number n by n. S (t) itself remains. on the other hand,
As for the noise component, the sum of the noise components up to the number of times of reading n is Σ (n = 1 to n) Nn (t), which is divided by n to obtain Σ (n = 1 to n) Nn (t) / n. Become. Since the sum of the noise components Nn (t) is canceled when there is a part where the phases do not match, if the sum is divided by the number n of times the sum is read, the absolute value Vp of the calculated noise component becomes the original value. It is smaller than the absolute value VZn of the noise component (Vp
≤ Vzn). Therefore, the target signal VzS
A signal in which only the noise component is reduced without changing the magnitude of the amplitude of (t) is output to the data determination unit (step 202).

The data discriminating section (step 202) discriminates data of the signal received from the reading process (step 201) or the reproduction signal arithmetic processing section (step 204). FIG. 5 is a flowchart illustrating a determination method of the data determination unit (step 202) shown in FIG. As shown in FIG. 5, this determination processing includes two determination steps (steps 41 and 42). Although not shown, the signal received in these discriminating steps is also amplified by an amplifier circuit, passed through a target frequency band by a filter circuit, is set to a certain disadvantage by an AGC circuit, and is processed using an error correction code. A determination is made. Also in this case, the order in which the signals pass through the amplification, filter, and AGC circuits is not limited to this.

In the data discriminating process, discrimination of a signal directly received from the reading process (step 201) is attempted (step 41). As a result, if data discrimination can be achieved only by the signal from the reading process, the next process (step 203)
If not, the process proceeds to step 42. In step 42, a discrimination is performed on the calculated signal output from the reproduction signal calculation processing unit 20 (step 204). If it can be determined here, it is determined that it can be determined, and the process proceeds to the next process (Step 203). If it cannot be determined, the process proceeds to a read retry process (Steps 205 to 208) described later, and the reading process is performed again (Step 20).
Return to 1). As described above, since the noise component of the calculated signal from the calculation processing unit 20 decreases as the number of times of re-reading in the same section increases, the achievement rate of data discrimination increases.

Referring to FIG. 2 again, if the data can be determined by the data determination section (step 202), the formed data is shifted to the next processing (step 203). That is, the determination data is output to a higher-level device (not shown),
The apparatus performs step 2 in order to read the next data section.
Move to 01. At the same time, the reproduction signal arithmetic processing unit 20
(Step 204) and the number-of-reading-times discriminating sections A to
A reset signal 1 is sent to C, and the process proceeds to the reading process of the next section (step 201). Each part that has received the reset signal 1 clears all the internal values and prepares for the data reading operation in the next section.

Next, a rereading (retry) process in the magnetic tape device of the present embodiment will be described. As shown in FIG. 2, when the data discrimination unit (step 202) fails to discriminate the data, the read count discriminating unit A first sets the number of reads for the data section at that time to a predetermined number of times. K (Step 20)
5). As a result, if the number of times has reached K, an error report is made to the host device, and at the same time, the occurrence of the error is notified to the outside using the display unit 17 (step 209), and the reset signal 1 is output to terminate the operation. As described above, the reset signal 1 is output from the reproduction signal calculation processing unit 20 and the read number determination units A to
C and the internal value is cleared. in this way,
When the number of times of reading has reached K times, the data section is determined to be unreadable and an error report is issued, so that the interruption of the processing due to the endless repetition of rereading of the apparatus is prevented.

If the number of re-reads is less than K times at the discriminating section A, the process proceeds to the number-of-reads determining section B, where the number of read times is compared with a predetermined number M (K> M). (Step 206). If the comparison has reached M times, the cleaning mechanism 13 automatically cleans the recording / reproducing head 12. Here, the automatic cleaning process of the recording / reproducing head uses a conventional technique, and a detailed description thereof is omitted here. After automatic cleaning,
Also, if the number of times of reading is less than M times, the process proceeds to the number-of-times-of-reading determining unit C (step 207).

In the reading number determination section C, the number of reading times is compared with a predetermined number L (K>L> M) (step 207). The request is displayed (step 211).
After this display and when the number of readings is less than L, the tape deck mechanism 11 is driven to rewind the magnetic tape (step 208). By this rewinding operation, the magnetic tape is rewound to the head of the section where the data could not be determined. After this rewinding operation, the reading process for the section is performed again (step 20).
1).

If the tape is ejected during the operation of the magnetic tape device 1, automatic cleaning is performed (step 2).
10) and the reset signal 2 is sent to the cleaning request (step 211) to clear the contents.

Although the embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments, and may be configured in various other forms. In particular, the embodiment of the present invention is not limited to a magnetic tape device and may be realized as another information reproducing device such as a magnetic disk device as long as a retry operation is performed at the time of reading information. The operation such as the above is not limited to this, and another method may be applied.

[0035]

As described above in detail, in the information reading method and the information reproducing apparatus according to the present invention, when performing the rereading operation of the section where the data could not be determined in the reading operation, the reading of the section is performed. All data is added and stored, and the noise component in this section is reduced by calculating multiple signals obtained by these retries, thereby improving the data discrimination by retry processing when reading data. I do. Therefore, the occurrence of an unreadable error can be avoided more preferably than in the prior art, and the reliability of the device can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an information reproducing apparatus according to the present invention.

FIG. 2 is a diagram illustrating an information reading method according to the present invention.

FIG. 3 is a diagram illustrating a calculation process of a reproduction signal calculation processing unit 20;

FIG. 4 is a diagram illustrating an operation of reducing a noise component by the arithmetic processing illustrated in FIG. 3;

FIG. 5 is a diagram illustrating a data determination method according to the information reading method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic tape apparatus 10 Magnetic tape apparatus main body 20 Reproduction signal operation processing part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G11B 20/18 572 G11B 20/18 572G

Claims (7)

[Claims] 1. An information reading method in which, when data read from an information storage medium cannot be determined by an information reading means, a data reading operation is repeated a plurality of times in a section in which the data cannot be determined to attempt data determination. An information reading method comprising calculating a plurality of data obtained in each of a plurality of reading operations to reduce a noise component other than a signal to be read and trying data discrimination. 2. The information reading method according to claim 1, wherein the calculation is performed after adding voltage levels on a same time axis for a plurality of data in the same section read in the plurality of reading operations. An information reading method, wherein a voltage level for each time axis is divided by the number of times the reading operation is performed for the section. 3. The information reading method according to claim 1, wherein the method comprises the steps of:
An information reading method, characterized in that data discrimination is attempted for one or both of the data obtained by the latest reading operation for the section where the data could not be determined. 4. The information reading method according to claim 1, wherein the number of times of the reading operation to the section where the data cannot be determined reaches a predetermined first number. An information reading method, wherein the means is automatically cleaned. 5. The information reading method according to claim 1, wherein when the number of read operations to the section where the data cannot be determined reaches a predetermined second number, an operator or a higher-level device is read. An information reading method, comprising issuing a cleaning request to an apparatus. 6. The information reading method according to claim 1, wherein when the number of times of the read operation to the section where the data cannot be determined reaches a predetermined third number, the data is not determined. An information reading method, characterized in that it is determined that it is possible to perform error processing. 7. A medium driving unit for driving an information storage medium, a signal reading unit for reading data from the storage medium, a data determination unit for determining data read by the information reading unit, and controlling operation of the apparatus. An information reproducing apparatus which, when it is not possible to determine the data read from the information storage medium, repeats a plurality of reading operations for a section in which the data cannot be determined and attempts data determination. Further, a memory means for storing a plurality of data obtained by a plurality of reading operations for the section in which the data cannot be determined, and a plurality of read data for the section in which the data cannot be determined are calculated. An information reproducing apparatus comprising: an arithmetic processing unit that reduces only a noise component of data in the section.