JPH031374A - Error correcting system for magnetic tape unit - Google Patents

Abstract

PURPOSE:To efficiently instruct an erroneous track by reducing the number of the erroneous tracks, which are already known, based on erroneous pattern holding information stored for the unit of each track. CONSTITUTION:In order to reduce the number of the erroneous tracks which are already known, an erroneous track instructing circuit 4 inquires the erroneous pattern holding information to an erroneous pattern generating circuit 8 and these erroneous pattern holding information show whether the already known erroneous track intermittently generates an erroneous pattern beforehand or not. When the erroneous pattern is not generated in the past, already known erroneous track information are made ineffective and the number of unknown erroneous tracks is reduced into the range of correcting ability. Then, the already known and unknown erroneous track information in the range of the correcting ability are inputted to the erroneous pattern generating circuit 8. The erroneous pattern generating circuit 8 generates the erroneous pattern and based on this erroneous pattern, an error correcting circuit 4 corrects an error. Thus, error correction can be efficiently executed even over the range of the correcting ability.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an error correction method in a magnetic tape device (prior art). Errors may occur in which data cannot be read normally due to a drop in level, loss of synchronization, etc.

To deal with such errors, we perform the following processing. First, when writing data on a magnetic tape, data is written in the running direction of the tape in units of a predetermined number of tracks, and an error correction code for the data on this track is written on the remaining tracks.

When data is read from the magnetic tape, the data read from the magnetic tape is input to the syndrome generation circuit 1 and the error correction circuit 6, as shown in FIG. Further, the error correction code read from the magnetic tape is input to the syndrome generation circuit 1. The syndrome generation circuit 1 generates a syndrome based on the input data and error correction code, and inputs it to the unknown error track detection circuit 3 and the error pattern generation circuit 5. The unknown error track detection circuit 3 detects an unknown error track (internal pointer information) based on the input syndrome and inputs it to the error pattern generation circuit 5.

On the other hand, the error detection circuit 7 checks the level of the output signal of each track, out of synchronization, etc., and when an abnormality is detected, adds external pointer information indicating that an abnormality has been detected to the known error track indicating circuit 2.

The known error track designation circuit 2 obtains track information in which an abnormality has occurred from this external pointer information and adds it to the error pattern generation circuit 5.

The error pattern generation circuit 5 performs the following processing based on this external pointer information, the syndrome input from the syndrome generation circuit 1, and the unknown error track information input from the unknown error track detection circuit 3. First, the error pattern generation circuit 5 performs the following processing.
It is determined whether the total number of tracks of known and unknown error track information is within the error correction capability. When the error correction capability is within the range, an error pattern is generated and input to the error correction circuit 6. The error correction circuit 6 takes the exclusive OR of this error pattern and the read data, and outputs the error-corrected data as output data.On the other hand, when the error correction capacity is exceeded, error correction is not possible. Information to that effect is input to the error correction circuit 6. The error correction circuit 6 outputs a message indicating that the error cannot be corrected as output data.

(Problem to be Solved by the Invention) By the way, errors do not necessarily occur in the read data of the track indicated by external pointer information. However, conventional error correction methods Based on the total number of tracks indicated by , it is unconditionally determined whether or not the total number of tracks is within the range of error correction capability.

Therefore, it may be determined that error correction is impossible even though no error has actually occurred. As described above, conventional error correction systems have problems that need to be solved.

The present invention has been made in view of the above circumstances, and its purpose is to calculate the number of known error tracks based on the error pattern holding information stored in each track when the error is out of the range of error correction capability. An object of the present invention is to provide an error correction method in a magnetic tape device that can efficiently indicate an erroneous track by reducing the error.

(Means for Solving the Problems) In order to achieve the above object, an error correction method in a magnetic tape device of the present invention records data and an error correction code for the data on a magnetic tape, and when reading the data, an error detection means based on external pointer information outputted by detecting an abnormality in the level of the read signal from the magnetic tape, and internal pointer information outputted by the unknown error track detection means based on the data and the error correction code. In an error correction method for a magnetic tape device in which error data is corrected according to an error pattern generated by an error pattern generation means, the present invention includes a storage means for storing error pattern retention information for each track, and the internal pointer information and the external pointer information. It is determined whether the number of error tracks shown is within the range of error correction capability, and if it is outside the range of error correction capability, it is determined whether the number of error tracks is within the range of error correction capability based on the error pattern holding information stored in the storage means. and error track indicating means for reducing the number of error tracks indicated by the external pointer information so that the number of error tracks indicated by the external pointer information is reduced.

(Function) In the error correction method in the magnetic tape device of the present invention, the storage means stores error pattern retention information for each track. Then, the error track indicating means determines whether or not the number of error tracks indicated by the internal pointer information and the external pointer information is within the range of the error correction capability, and if it is outside the range of the error correction capability, it is stored in the storage means. The number of error tracks indicated by the external pointer information is reduced so that it is within the error correction capability range based on the error pattern holding information that has been stored.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. In this figure, the same reference numerals as in FIG. 2 indicate the same parts.

The error pattern generation circuit 8 has an additional function of storing error pattern holding information for each track, that is, error patterns generated in each track. The error track indication circuit 4 determines the total number of tracks, including the number of known error tracks and the number of unknown tracks, and when the total number of tracks exceeds the correction capacity, the error track indication circuit 4 determines the total number of tracks, including the number of known error tracks and the number of unknown tracks, and when the total number of tracks exceeds the correction capability, the error track indication circuit 4 determines the total number of tracks, and when the total number of tracks exceeds the correction capacity, the error track indication circuit 4 determines the total number of tracks, including the number of known error tracks and the number of unknown tracks. Reduce the number of known error tracks to within the correction capability range.

Next, the operation of this embodiment will be explained with reference to FIG. Syndrome creation episode? 81 generates syndromes based on data and error correction codes. and,
The unknown error track detection circuit 3 detects an unknown error track based on this syndrome and inputs the detected error track to the error track indicating circuit 4. Known error track indicating circuit 2 detects a known error track based on external pointer information from error detection circuit 7 and inputs the detected error track to error track indicating circuit 4 .

The error track designation circuit 4 determines the total number of tracks designated by the input known and unknown error tracks, determines whether or not it is within the range of error correction capability, and performs the next process.

(2) When within the range of error correction capability In such a case, error track information (unknown and known error tracks) is input to the error pattern generation circuit 8.

The error pattern generation circuit 8 generates an error pattern based on this error track information and the syndrome received from the syndrome generation circuit 1, and inputs it to the error correction circuit 6. The error correction circuit 6 performs an OR operation on this error pattern and data, corrects the error data, and outputs the corrected data.

■When the error correction capability is outside the range In such a case, the error track indication circuit 4 reduces the number of known error tracks.First, it determines whether the known error track has been generating an error pattern intermittently or not. The error pattern generation circuit 8 is inquired about error pattern holding information indicating whether the error pattern is retained or not. Then, it is determined whether or not this error pattern retention information indicates that an error has occurred in the past, and if no error pattern has occurred in the past, the known error track information is invalidated and the number of known error tracks is Reduce it to within the range of correction ability. Then, known and unknown error track information within the correction capability range is input to the error pattern generation circuit 8.

The error pattern generation circuit 8 generates an error pattern based on the unknown and known error track information as described above, and the error correction circuit 6 corrects the data based on this error pattern.

(Effects of the Invention) As explained above, in the error correction method in the magnetic tape device of the present invention, when known and unknown error track information that is outside the range of error correction capability is given, error pattern retention information is used to correct errors. It is determined whether or not a track has intermittently generated an error pattern before, and the number of given known error tracks is reduced. Therefore, if the error correction method in the magnetic tape device of the present invention is adopted, Even when the unknown number of error tracks exceeds the range of error correction capability, error correction can be performed efficiently.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional error correction system. DESCRIPTION OF SYMBOLS 1... Syndrome creation circuit, 2... Known error track instruction circuit, 3... Unknown error track detection circuit, 4
...Error track indication circuit, 5, 8...Error pattern generation circuit, 6...Error correction circuit, 7...Error detection path.

Claims (1)

[Scope of Claims] External pointer information is output when data and an error correction code for the data are recorded on a magnetic tape, and when an error detection means detects an abnormality in the level of a read signal from the magnetic tape during reading. Error correction in a magnetic tape device in which error data is corrected according to an error pattern generated by an error pattern generation means based on the data and internal pointer information outputted by the unknown error track detection means based on the data and the error correction code. The system includes a storage means for storing error pattern holding information for each track, and determining whether or not the number of error tracks indicated by the internal pointer information and external pointer information is within the range of error correction capability. and error track indicating means for reducing the number of error tracks indicated by the external pointer information so that the number of error tracks is within the error correction capability range based on the error pattern holding information stored in the storage means. An error correction method in a magnetic tape device characterized by: