JP2857571B2 - Method and apparatus for recognizing marks on magnetic tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for recognizing marks on a magnetic tape, and is used, for example, for tape format control in a small cartridge tape device.

A small cartridge tape device is often used as an external storage device of a computer. In the small cartridge tape device, the transition from 18 tracks to 36 tracks has been performed, and the increase in recording capacity by double-density tape, double-length tape, and the like has been progressing.
Along with this, the method of error correction of customer data is also shifting to a method of higher accuracy.

In order to perform tape format control in a small cartridge tape device, it is necessary to recognize a mark recorded on a magnetic tape. If there is a mark recognition error, the error can be corrected in a short time by a recovery function. It is desirable to maintain the reliability of the system.

[0004]

2. Description of the Related Art Conventionally, marks for controlling a tape format are recognized as follows. That is, based on the track data read from each track, a pattern of a plurality of zones each including a group of a plurality of tracks is respectively identified, and a mark is recognized based on the identified pattern of each zone. I have.

For example, in the case of a magnetic tape having 18 tracks, as shown in FIG. 7, tracks 0a to 8a, 0b
To 8b (ECC tracks). These tracks, as shown in FIG.
Each track is grouped and divided into six zones A to F.

The same pattern is recorded on three tracks belonging to the same zone. If all or two or more of the three track data read from the three tracks are the same, the pattern is recorded in the zone. Is determined to be a pattern. Based on a total of six patterns for each zone determined in this manner, what mark is recognized.

FIG. 9 is a diagram showing the correspondence between marks and patterns in each zone. For example, when the pattern of six zones is “1T1TT1”, it is “DID
18 "mark. Here, the pattern “1” is “ALL1 pattern”, and all bits are indicated by “1” as shown in FIG. The pattern “T” is a “TONE pattern”, which is indicated by a repetition of a 6-bit pattern consisting of “100000”. Note that these matters regarding the mark are defined in ANSI standard X3B5 / 92-48.

[0008]

When reading a magnetic tape, data reading errors (reading errors) may occur due to deterioration of the magnetic tape, defective media, or adhesion of dust. When a reading error occurs, if the mark can be determined within the minimum error distance between the marks, the mark is output.

However, in the case where it cannot be determined by the minimum error distance, a signal that cannot be recognized is set only in the related art, and does not have a recovery function for a reading error.

For example, a mark "DID18" shown in FIG.
And “WRAP”, the patterns of the four zones A to D are the same, and the patterns of the two zones E and F are different, so the minimum error distance is 6 (= 2 zones × 3 tracks). . Therefore, for example, when a reading error occurs on three tracks (one zone), the two can be determined. However, when a reading error occurs on six tracks (two zones), the two cannot be determined. The mark cannot be recognized.

Therefore, conventionally, in such a case, retry control is performed, and the same portion of the magnetic tape is read again. For this reason, error correction takes time, and in the case of a defective magnetic tape, error correction cannot be performed even if retry control is performed, which has been a factor that hinders improvement in system reliability. .

The present invention has been made in view of the above-described problems, and when a reading error of a magnetic tape occurs, a mark is recognized by performing error correction quickly without performing retry control, and system reliability is improved. It aims at improvement.

[0013]

According to the first aspect of the present invention, there is provided a method for solving the above-mentioned problems, as shown in FIGS. A pattern PT of a plurality of zones each comprising a group of a plurality of tracks, and a mark MK is recognized based on the identified pattern PT of each zone.
This is a recognition method for recognizing the mark MK based on only the identifiable zone when there is a zone in which the mark MK cannot be identified.

According to a second aspect of the present invention, there is provided a method comprising:
When there is a zone in which T cannot be identified, recognition of the mark MK is performed based on only the zone that can be identified, and when there are a plurality of recognized marks MK, a threshold for pattern identification in the zone that cannot be identified. This is a recognition method in which the mark MK is recognized by lowering the value SL and increasing the identifiable zone.

According to a third aspect of the present invention, there is provided a method comprising:
When there is a zone in which T cannot be identified, the mark MK is recognized based only on the identifiable zone. When there are a plurality of recognized marks MK, the mark MK is recognized prior to the recognition of the mark MK. This is a recognition method for recognizing the mark MK with reference to one or more adjacent marks.

According to a fourth aspect of the present invention, there is provided a method comprising:
When there is a zone in which T cannot be identified, recognition of the mark MK is performed based on only the zone that can be identified, and when there are a plurality of recognized marks MK, a threshold for pattern identification in the zone that cannot be identified. When the value SL is lowered and there are a plurality of marks MK that are still recognized,
An adjacent one recognized before the recognition of the mark MK
This is a recognition method for recognizing the mark MK with reference to one or a plurality of marks.

An apparatus 2 according to a fifth aspect of the present invention includes an inference unit 13 that recognizes a mark MK based on only a zone in which a pattern PT can be identified, and outputs one or a plurality of recognized marks MK. Has a transition table TT indicating a correspondence between a recognized mark and a mark MK expected this time, and a register 16 for storing a mark recognized in the past. Then, based on the past marks stored in the register 16, the mark MK is recognized by referring to the transition table TT.

[0018]

The inference unit 13 recognizes the mark MK based on only the zone in which the pattern PT can be identified, and outputs one or a plurality of marks MK. If there is one mark MK, it is recognized as a mark MK.

When there are a plurality of marks MK, for example, the threshold value SL is lowered. If the number of marks MK is reduced to one, the mark MK is recognized as the mark MK. In addition, from the plurality of marks MK output by the inference unit 13, based on the contents of the register 16, referring to the transition table TT,
One mark MK is determined.

[0020]

FIG. 1 is a block diagram of a recognition device 2 according to the present invention. In FIG. 1, the recognition device 2 includes pattern identification ROMs 11a to 11f for performing pattern identification for each zone,
A mark recognition ROM 12 for recognizing a mark based on all the identification codes DCD output from the pattern identification ROMs 11a to 11f, and an identification code DCD for which pattern identification was possible among the identification codes DCD output from the pattern identification ROMs 11a to 11f. It comprises an inference ROM 13 for inferring a mark based only on the above, a format monitoring unit 14, a mark transition ROM 15, a register 16, and the like.

To each of the pattern identification ROMs 11a to 11f, a TONE signal and a VOID signal created based on track data read from each track of the magnetic tape are inputted for three tracks belonging to each zone. I have.

Here, the TONE signal is a signal which is set by detecting a TONE pattern, and is reset when a peak pulse in NRZ1 [non-return to zero (1) recording] continuously exists for 3 bit cells. . The VOID signal is a signal that is set when a peak pulse does not exist for 7 bit cells or more, and is reset by detecting the peak pulse. Therefore, when the TONE signal is on and the VOID signal is off, the track pattern is identified as the TONE pattern, and when both the TONE signal and the VOID signal are off, the track is identified as the ALL1 pattern.

Each of the pattern identification ROMs 11a to 11f identifies the pattern of each zone based on the TONE signal and the VOID signal for the three tracks, and outputs the identification result as 4
It is output as a bit identification code DCD.

The zone of the identification code DCD is TO
Information indicating whether the pattern has been identified as the NE pattern or the ALL1 pattern, information indicating the number of tracks on which a reading error has occurred, and the like are included.

The pattern identification ROMs 11a to 11f can change the method of determining from the patterns of the three tracks by the threshold SL when identifying the pattern of the zone.

That is, when the threshold value SL is "3", the pattern of the zone is determined only when the patterns of the three tracks are all the same. When the threshold value SL is “2”, when two or more tracks have the same pattern, the pattern is determined as a zone pattern. When the threshold SL is set to “1”, if the pattern of one track can be identified, even if the other two tracks have a reading error,
The pattern of the identified track is determined as the pattern of the zone. The value of the threshold value SL is, for example, "3" at the time of inspection after writing the pattern on the magnetic tape, "2" at the time of normal reading, and at the time of error correction described later (step # 15 in FIG. 2). “1” is set respectively.

When all of the pattern identification ROMs 11a to 11f can identify a pattern, the mark recognition ROM 12 recognizes the mark based on the identification code DCD and outputs the recognized mark (MKa). It is conventionally known.

The inference ROM 13 is a pattern identification ROM 1
Even when the pattern cannot be identified in any of 1a to 1f, the mark is inferred and recognized based only on the identification code DCD that has been identified, and one or more recognized marks are output. Things.

For example, if the two zones A and B are identified as “T” and “1”, respectively, and the four zones C to F cannot be identified, the pattern input to the inference ROM 13 is “ T1XXXX ". According to FIG. 9, a possible mark in this case is “DID3
6 "," ERS "and" TM ". Therefore, in this case, the inference ROM 13 outputs these three marks MK.

The output of the inference ROM 13 is, for example,
Each mark is assigned to one bit and output as 10-bit data so that 0 marks can be output independently. The inference ROM 13 stores an inference table for obtaining a 10-bit output corresponding to the contents of the six identification codes DCD.

The mark transition ROM 15 predicts the current mark from the transition state based on the marks recognized in the past two times before the recognition of the current mark.

Here, the mark M recorded on the magnetic tape
The arrangement of K will be described with reference to FIGS. FIGS. 5 and 6 are views showing an example of the mark MK recorded on the magnetic tape TP.

For example, in FIG. 5, “DID (d) is set in an area within a specified length from the beginning (BOT) of the magnetic tape TP.
"identity identification" is recorded, and then "IDS (ID-separato)" is recorded.
r) "" IBG (interblock gap) "
"SPM (special mark merge)
1 "is recorded.

In the case of 36 tracks, "W" for controlling the folding of the magnetic tape TP is provided near the end (EOT) of the magnetic tape TP in the forward (FWD) direction.
RAP "," SPM3 "," IBG ", etc., and a similar mark MK is also recorded in the backward (BWD) direction.

Since these marks MK are recorded based on their respective functions for controlling the tape format, they have regularity with respect to their arrangement. Therefore, when it is difficult to recognize the mark MK at a certain position, it is possible to recognize most of the marks MK by referring to one or more adjacent marks recognized before the recognition of the mark MK. .

Therefore, in this embodiment, the transition tables TT1 and TT2 indicating the correspondence between the mark MK recognized twice in the past and the mark MK expected this time in the forward direction and the backward direction conform to the ANSI standard. Mark transition R created based on the specified tape format
It is stored in OM15.

FIG. 3 is a diagram showing a transition table TT1 in the forward direction, and FIG. 4 is a diagram showing a transition table TT2 in the backward direction. For example, according to the transition table TT1 in FIG. 3, if there is no mark MK in the past two times, “DID” is expected. If “IDS” and “IBG” are sequentially recognized in the past two times, one of “SPM1,” “SPM2,” and “DB” is expected this time.

Transition table TT of mark transition ROM 15
1 and TT2 are switched by a reading direction designation signal (F / B). The register 16 stores marks recognized twice in the past.

The mark transition ROM 15 is the inference ROM 13
When there are a plurality of marks MK output from the register, based on the contents of the register 16, the current mark MK is predicted with reference to the transition tables TT1 and TT2, and a match between them is recognized and output as the current mark. .

Next, a procedure for recognizing the mark MK by the recognizing device 2 will be described with reference to a flowchart. FIG. 2 is a flowchart showing a procedure for recognizing a mark by the recognition device 2.

When the reading of the magnetic tape TP is started, the TONE obtained from the read track data is read.
Pattern P of each zone based on the signal and VOID signal
T is identified (# 10). If the mark can be recognized by the mark recognition ROM 12 based on the identified pattern (Yes in # 11), the mark MK
is output (# 21).

Since there is an error zone, mark recognition RO
If recognition by M12 is impossible (No in # 11), the error zone is determined (# 12), and inference is performed by the inference ROM 13 to output one or a plurality of marks MK (#). 13).

When the mark output from the inference ROM 13 is 1
If it is one (Yes in # 14), the mark MK
b is output (# 22). If there are a plurality of marks (No in # 14), the threshold value SL of the pattern identification ROMs 11a to 11f is lowered (# 15), and then the inference ROM 13 is read again.
(# 16), and if there is one mark, the mark MKb is output (# 23).

If there are still a plurality of marks, the mark MKc is output from the mark transition ROM 15 with reference to the transition table TT based on the contents of the register 16 (# 18).

As described above, when there is no error zone, the mark MKa recognized by the mark recognition ROM 12 is output as in the prior art. However, the recognition by the mark recognition ROM 12 becomes impossible because of the error zone. In this case, first, the recognition of the mark MK is tried based on the pattern of the zone other than the error zone. If the recognition is still impossible, the threshold SL is lowered to try the recognition of the mark MK. If so, the current mark MK is recognized based on the mark MK recognized in the past.

Therefore, even when there is an error in reading the magnetic tape TP, the mark is recognized based on the obtained information, the error is corrected without performing retry control, and the mark is recognized. Can be done quickly. In addition, even when the retry control is used together, the mark recognition rate is improved as compared with the related art, and in any case, the reliability of the system is improved.

When the mark cannot be recognized by the mark recognition ROM 12, the threshold SL is not immediately lowered, but the recognition is performed by the inference ROM 13 first. When a plurality of marks cannot be determined, the threshold SL is lowered. In addition, a decrease in reliability due to a decrease in threshold SL is minimized.
Further, when there are a plurality of marks output from the inference ROM 13, a mark that matches the one expected as the current mark is selected with reference to the transition table TT, so that high reliability is maintained in recognition of the mark. Is done.

In the above embodiment, the inference by the inference ROM 13 and the transition table T by the mark transition ROM 15
The reference to T and the lowering of the threshold SL may be applied in an order and combination other than those described above. When decreasing the threshold value SL, the threshold value SL may be decreased in the order of “3”, “2”, “1”.

In the above embodiment, the mark recognition ROM
12, the mark MKa may be output by the inference ROM 13 even when there is no error zone. The number of past marks in the transition table TT may be one or three or more. As a configuration of the transition table TT, for example, for each combination of marks recognized in the past,
All expected marks MK for each may be indicated. Instead of or in addition to the inference ROM 13 and the mark transition ROM 15, etc., a table stored in an appropriate external storage device, a RAM to which the table is transferred, a table or program stored in a main storage device, or a hard logic may be used. Good. In addition, the configuration of the recognition device 2,
The contents and configuration of each table, the contents or order of the flowchart, and the like can be variously changed in addition to the above in accordance with the gist of the present invention.

[0050]

According to the present invention, when a reading error occurs in a magnetic tape, marks are recognized by performing error correction quickly without performing retry control, thereby improving the reliability of the system. Can be.

According to the second aspect of the present invention, the mark recognition rate is further improved. According to the third and fourth aspects of the invention, the mark recognition rate is further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a recognition device according to the present invention.

FIG. 2 is a flowchart showing a procedure for recognizing a mark by the recognition device.

FIG. 3 is a diagram showing a transition table in a forward direction.

FIG. 4 is a diagram showing a transition table in a backward direction.

FIG. 5 is a diagram showing an example of a mark recorded on a magnetic tape.

FIG. 6 is a diagram illustrating an example of a mark recorded on a magnetic tape.

FIG. 7 is a diagram showing a TONE pattern and an ALL1 pattern recorded on a track of a magnetic tape.

FIG. 8 is a diagram showing the correspondence between tracks and zones on a magnetic tape.

FIG. 9 is a diagram showing a correspondence relationship between a mark and a pattern of each zone.

[Explanation of symbols]

 2 Recognition device 13 Inference ROM (inference unit) 16 Register PT pattern MK mark SL Threshold TT Transition table

Claims (5)

(57) [Claims] 1. A pattern (P) for a plurality of zones each comprising a plurality of track groups based on track data read from each track of a magnetic tape.
T) is identified, and the mark (MK) is identified based on the identified pattern (PT) of each zone. If there is a zone where the pattern (PT) cannot be identified, identification is possible. A mark pattern recognition method for a magnetic tape, comprising: recognizing a mark (MK) based only on a specific zone. 2. A pattern (P) for a plurality of zones each comprising a plurality of track groups based on track data read from each track of a magnetic tape.
T) is identified, and the mark (MK) is identified based on the identified pattern (PT) of each zone. If there is a zone where the pattern (PT) cannot be identified, identification is possible. The mark (MK) is recognized based on only the unique zone, and when there are a plurality of recognized marks (MK), the threshold (SL) of the pattern identification in the unidentifiable zone is lowered to enable identification. A method for recognizing a mark on a magnetic tape, comprising recognizing a mark (MK) by increasing a zone. 3. A pattern (P) for a plurality of zones each comprising a plurality of track groups based on track data read from each track of a magnetic tape.
T) is identified, and the mark (MK) is identified based on the identified pattern (PT) of each zone. If there is a zone where the pattern (PT) cannot be identified, identification is possible. In addition to performing mark (MK) recognition based on only the relevant zone, and when there are a plurality of recognized marks (MK), one or more adjacent marks recognized prior to the recognition of the mark (MK) And recognizing the mark (MK) with reference to FIG. 4. A pattern (P) for a plurality of zones each comprising a plurality of track groups based on track data read from each track of a magnetic tape.
T) is identified, and the mark (MK) is identified based on the identified pattern (PT) of each zone. If there is a zone where the pattern (PT) cannot be identified, identification is possible. The mark (MK) is recognized based on only the unique zone, and when there are a plurality of marks (MK) to be recognized, the threshold (SL) for pattern identification in the unidentifiable zone is lowered, and the mark (MK) is still recognized. When there are a plurality of marks (MK), the mark (MK) is recognized with reference to one or more adjacent marks recognized before the recognition of the mark (MK). A method for recognizing marks on magnetic tape. 5. A pattern (P) for a plurality of zones each comprising a plurality of track groups based on track data read from each track of the magnetic tape.
T), respectively, and a device (2) for recognizing a mark (MK) based on the pattern (PT) of each identified zone, wherein the mark (MK) is marked based only on the zone where the pattern (PT) can be identified An inference unit (13) for recognizing (MK) and outputting one or more recognized marks (MK); a mark recognized in the past and a mark (M
K), a transition table (TT) indicating a correspondence with the register, and a register (16) for storing a mark recognized in the past.
When a plurality of marks are recognized by the inference unit (13), the mark () is referred to by referring to the transition table (TT) based on the past marks stored in the register (16). MK) recognition apparatus for recognizing marks on a magnetic tape.