JPS5825293B2 - Data display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a data correction control method, in particular, a syndrome obtained from data with an error correction code and a position where an error is suspected to have occurred, which indicates where the error is, if any. In the data correction control system that automatically corrects errors based on the information, the extraction conditions of the pointer system that extracts the information on the suspected error location are changed according to the state information at the time of control and/or the number of tries. The present invention relates to a data correction 1 control method that increases the possibility of correct error correction.

Although the present invention is not limited thereto, for example, in magnetic tape devices for information processing, the recording density on the medium has recently become extremely dense.

As the density increases, the influence of dust and defects on the medium increases, and it becomes increasingly difficult to reproduce the signal.

In order to solve these problems, an error correction code is used, and a method is adopted in which the error correction code is attached to the data and written on the medium, and when it is read, a syndrome is generated to perform automatic error correction. has been done.

As a further development of this method, in addition to correcting errors caused by the syndromes described above, if an error has occurred, it is possible to extract the suspected error track/information that indicates in which track it is present. In conjunction with the above-mentioned syndrome, a system has been adopted that allows errors to be automatically corrected not only in one track but also in cases where errors occur in two tracks.

In this developed method, when extracting the information on the suspected error track, the data read from the medium (including the error correction code) is inspected for signal amplitude and phase shift under stricter conditions. be done.

When it is discovered that an error exists due to the syndrome, the suspect track information is always extracted, and conversely, when the suspect track information is extracted, an error is always found due to the syndrome. It is necessary that the

However, it is not easy to properly extract information on a track suspected of causing an error so that the conditions are correctly obtained.

In other words, (1) If it is made easier to generate error track information, more information will be generated than the error correction function of the system, and even though the error is actually within the error correction function, the error will be detected. It will become impossible to correct.

In other words, if the error correction function of the system is within 2 tracks, the information on the suspected error track is 3.
If you list more than 1, it becomes impossible to correct the error even if it actually occurs within 2 tracks.

(2) Also, by making it difficult to generate error track information, even if it is determined from the syndrome that an error has occurred on, for example, two tracks, the suspect track information is not listed and the error can be corrected. It disappears.

The present invention aims to solve the above points,
To increase the possibility of error correction as much as possible by changing the conditions for extracting the information on the suspected error location according to the control state during data reproduction and/or the number of tries. It is an object.

Therefore, the data correction control method of the present invention adds an error correction code to the given data, and when the data is used, the data correction control method automatically corrects the error using the error correction code. The method includes a demodulation circuit that reproduces each bit information of data including the error correction code, a syndrome generation circuit that generates a syndrome in the output reproduced by the demodulation circuit, and conditions for reproducing bit information by the demodulation circuit. A pointer system that inspects each of the above-mentioned bit information under strict conditions and detects the suspected error position, and an error correction pattern creation that creates an error correction pattern based on the above syndrome and the above information on the suspected error position. The present invention is characterized in that a circuit is provided so that the bit information reproduction conditions in the pointer system are changed in accordance with control state information such as during data reproduction and/or the number of tries.

This will be explained below with reference to the drawings. The figure shows the configuration of an embodiment of the present invention.

In the figure, reference numeral 1 denotes a read head, for example, nine pieces are provided corresponding to each trunk of nine tracks on a magnetic tape, and reference number 2 denotes a demodulation circuit that reproduces the read bit information from each of the nine tracks. 3 is a data buffer in which 9-bit bit information corresponding to each reproduced track is sequentially set and held; 4 is a data buffer for syndrome 8;
1 generation circuit which calculates syndrome S1 based on bit information from tracks "o" to "7" corresponding to data parts and track "p" corresponding to parity bit p; 6 is a syndrome 82 generating circuit which calculates syndrome S2 based on the bit information from tracks "0" to "7" corresponding to the data part; 6 is a pointer system which indicates each read 7 is an error correction pattern creation circuit which reproduces the bit information under stricter conditions than the demodulation circuit 2 and extracts the information on the suspected error track. 8 is an error correction circuit that automatically converts the data held in the data buffer 3 according to the above correction pattern. 9 is an extraction condition selection circuit that determines the extraction conditions in the pointer system 6; 10 is a control condition setting section that automatically or manually adjusts the settings according to the control status such as during data reproduction. What is set in
11 is the IJ l-retry count setting unit where the retry count is set; 12 is the syndrome S1 transfer bus; 13
14 represents the syndrome S2 transfer bus, and 14 represents the error suspected truck information transport bus.

Further, the reference numeral 15 shown in the upper left of the figure is a magnetic tape, and on the magnetic tape 15 there are, for example, tracks "0" to "7".
Information on nine tracks consisting of data 16 and rpJ is recorded as one group of data 16.

An error correction code FCC is recorded at the end of the first group of data 16, and the code FCC is used for detecting and correcting error occurrence, which will be described later.

In addition, when extracting information on a suspected error track by the pointer system 6, for example, (i (ii) There is distortion or waveform deviation in the reproduced signal from the tracks consisting of: (ii) the reproduction signal from the tracks consisting of:
(iii) When it is found that the reproduced signal from a track does not meet pre-specified conditions, a point is given as there is a possibility that an error has occurred in the track. .

In the case of the present invention, the conditions for determining the above (1), (ii), and Gii), such as the level determination threshold in the case of level determination, are configured to be variable.

Prior to explaining the present invention, error correction processing by a conventional system will be briefly explained.

That is, the bit information from each of the nine tracks read by the read head 1 (there are actually nine tracks) is reproduced track by track by the demodulation circuit 2 and set in the data buffer 3 in sequence.

At this time, the bit information from tracks "0" to "7" and "p" is led to the syndrome 81 generation circuit,
As the information in the first group of data 16 is read out sequentially, intermediate calculation results of syndrome S1 are obtained, and 1
Error correction code FCC at the end of group data 16
When all the information is read correctly, the syndrome S1 becomes a bit string of all zeros.

Further, the bit information from tracks "0" to "7" is led to the syndrome 82 generation circuit, and when the error correction code FCC of the first group of data 16 has been read in the same way as above, unless an error has occurred, Syndrome S
2 is a bit string of all zeros.

Meanwhile, the bit information from each of the nine tracks read by head 1 is directed to pointer system 6, which points to
In system 6, each bit was reproduced under conditions even more severe than in demodulation circuit 2, and data buffer 3
If it is assumed that an error has occurred in the bit information set in the bit information, error suspected track information indicating which track the bit information belongs to is generated.

The error suspected track information is then notified to the error correction pattern creation circuit 7.

The error correction pattern creation circuit 7
1 and 82 and information on the suspected error track, an error correction pattern is output that specifies the bit position where the error has occurred.

The error correction circuit 8 obtains correction data as described above based on the pattern.

The system can perform error correction based on the above pattern when an error occurs in two tracks or less, but the error correction ability is limited when an error occurs in three or more tracks. It can be considered that the process is limited to simply detecting errors.

In the case of the conventional data correction control system as described above, if an error occurs on two tracks, for example, as described at the beginning of this specification, the pointer system 6 correctly extracts information on the two error-prone tracks. It is hoped that there will be.

However, in this case pointer system 6 always correctly points to 2
It is not always the case that information on a single error-prone track is extracted.

For this reason, even if the error could originally be corrected, it may become impossible to correct the error.

That is, it is difficult to always keep the extraction conditions by the pointer system 6 appropriate.

Therefore, in the case of the present invention, the extraction conditions of the pointer system are changed depending on the reading state while reading data, and/or the number of retries when an error occurs and retry processing is started. I'm trying to get it.

For example, during reading in this type of magnetic tape device, a preamble and a postamble are created on the magnetic tape for synchronization and the like.

While reading such preambles and postambles, it is necessary to read them under stricter conditions than when reading data.

Therefore, in the case of the present invention, for example, the illustrated control condition setting section 10 is set to indicate that a preamble is being read, and the extraction condition in the pointer system 6 is tightened via the extraction condition selection circuit 9.

Also, when reading data, if an error condition is expected, that fact is set in the control condition setting section 10 to adjust the extraction conditions in the pointer system 6.

That is, the extraction conditions are adjusted depending on the tape speed, for example.

In this type of system, if an uncorrectable error occurs when data is read under certain extraction conditions, the data is read again, ie, retried.

In such a case, countermeasures are taken, such as setting the number of retries to be executed in the retry number setting section 11 and, for example, gradually loosening the extraction conditions as the number of retries increases.

As explained above, according to the present invention, the extraction conditions of the pointer system 6 are changed as appropriate to enable extraction of appropriate error-prone track information, thereby increasing the possibility of correct error correction. can.

That is, for example, if the syndrome side is instructed that an error has occurred on two tracks, by appropriately changing the above extraction conditions, the two tracks can be pointed as the error-prone tracks. This enables error correction operations.

Incidentally, by changing the extraction conditions of the pointer system, in some cases, even if an error has actually occurred in three or more tracks and it is impossible to correct the error, the error may occur in less than two tracks. There may be cases in which the error is corrected incorrectly, assuming that it is an error.

However, although a detailed explanation will be omitted, error check codes are eventually prepared in blocks corresponding to multiple groups of data 16, 16, etc. on the magnetic tape 15. The system is designed to detect if an erroneous modification as described above is made.

Therefore, even if an incorrect correction is made according to the present invention, the incorrect correction will not be used in the utilization device.

[Brief explanation of drawings]

The figure shows the configuration of an embodiment of the present invention. In the figure, 1 is a read head, 2 is a demodulation circuit, 3 is a data buffer, 4 and 5 are syndrome generation circuits, 6 is a pointer system, 7 is an error correction pattern generation circuit, 8
9 represents an error correction circuit, 9 represents an extraction condition selection circuit, 10 represents a control condition setting section, and 11 represents a retry number setting section.

Claims (1)

[Claims] 1 In a data correction control method in which an error correction code is added to the given data and the error is automatically corrected using the error correction code when the data is used, the data containing the error correction code is a demodulation circuit that reproduces each bit of information, a syndrome generation circuit that generates a syndrome in the output reproduced by the demodulation circuit, and a test of each of the bits of information under conditions that are more severe than the conditions for reproducing the bit information by the demodulation circuit. and a pointer system for detecting the suspected error position, and an error correction pattern creation circuit for creating an error correction pattern based on the syndrome and the information on the suspected error position. A data modification control method characterized in that conditions are changed according to state information during control and/or the number of retry attempts.