JPH0757391A - Recognizing method of mark in magnetic tape and device therefor - Google Patents

Abstract

PURPOSE:To recognize a mark by quickly correcting an error even when retrial control is not performed and to improve the reliability of a system when the reading error of a magnetic tape arises in a method and a device for recognizing the mark of the magnetic tape. CONSTITUTION:This device is provided with an inference ROM 13 recognizing a mark based on only a zone capable of identifying a pattern and outputting recognized one or plural marks MK, a transition table TT designating the correspondence between the mark recognized in the past and a mark expected this time and a register 16 for storing the mark recognized in the past. When plural marks are recognized by means of the inference ROM 13, based on the past mark stored in the register 16, the mark is recognized by referring to the transition table TT.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mark recognizing method and a recognizing device for a magnetic tape, and is used 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 a small cartridge tape device, the number of tracks has been changed from 18 tracks to 36 tracks, and the high recording capacity is being increased by using a double-density tape or a double-length tape.
Along with this, the method of error correction of customer data is also shifting to a more accurate method.

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. When a mark recognition error occurs, the recovery function corrects the error in the shortest possible time. Therefore, it is desirable to maintain the reliability of the system.

[0004]

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

For example, in the case of an 18-track magnetic tape, as shown in FIG. 7, 0a to 8a, 0b are provided in each track.
Track numbers (ECC tracks) of 8b are assigned. These tracks have 3 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, and when all or two or more of the three track data read from them are the same, the pattern is recorded in that zone. It is determined to be a pattern. Based on the total of 6 patterns for each zone determined in this way, what kind of mark is recognized.

FIG. 9 is a diagram showing the correspondence between marks and patterns of each zone. For example, if the pattern of 6 zones is "1T1TT1", it is "DID
18 "mark is recognized. Here, the pattern "1" means "ALL1 pattern", and all bits are indicated by "1" as shown in FIG. The pattern “T” is a “TONE pattern” and is represented by repeating a 6-bit pattern consisting of “100000”. It should be noted that these matters regarding marks are specified in ANSI standard X3B5 / 92-48.

[0008]

When reading a magnetic tape, a data reading error (reading failure) may occur due to deterioration of the magnetic tape, defective media, dust adhesion, or the like. When a read error occurs, if the marks can be discriminated within the minimum error distance between the marks, the marks are output.

However, when it is not possible to discriminate by the minimum error distance, in the past, only an unrecognizable signal is set and there is no recovery function for a read error.

For example, the mark "DID18" shown in FIG.
And “WRAP” have the same four zones A to D and different zones E and F, the minimum error distance is 6 (= 2 zones × 3 tracks). . Therefore, for example, both can be discriminated even when a read error occurs in 3 tracks (1 zone), but when a read error occurs in 6 tracks (2 zones), the both cannot be discriminated. The mark cannot be recognized.

Therefore, in the past, retry control was performed in such a case, and the same portion of the magnetic tape was read again. Therefore, it takes time to correct the error, and even if retry control is performed when the magnetic tape is defective, the error cannot be corrected, which is one of the factors that hinder the improvement of system reliability. .

In view of the above-mentioned problems, the present invention quickly corrects an error and recognizes a mark when a read error occurs in a magnetic tape without performing retry control, thereby improving system reliability. The purpose is to improve.

[0013]

In order to solve the above-mentioned problems, the method according to the invention of claim 1 uses track data read from each track of a magnetic tape as shown in FIGS. A pattern PT of a plurality of zones each composed of a group of a plurality of tracks, and a mark MK is recognized based on the identified pattern PT of each zone.
Is a recognition method for recognizing the mark MK based on only the identifiable zone when there is a zone in which the identification is not possible.

The method according to the invention of claim 2 is the pattern P
When there is a zone in which T cannot be identified, the mark MK is recognized based on only the zone that can be identified, and when there are a plurality of recognized marks MK, the pattern identification threshold in the zone that cannot be identified. This is a recognition method for recognizing the mark MK by lowering the value SL and increasing the identifiable zone.

The method according to the invention of claim 3 is the pattern P
When there is a zone in which T cannot be identified, the mark MK is recognized based only on the identifiable zone, and when there are a plurality of recognized marks MK, the mark MK is recognized prior to the recognition. It is a recognition method for recognizing the mark MK by referring to one or more adjacent marks.

The method according to the invention of claim 4 is the pattern P
When there is a zone in which T cannot be identified, the mark MK is recognized based on only the zone that can be identified, and when there are a plurality of recognized marks MK, the pattern identification threshold in the zone that cannot be identified. When the value SL is set low and there are a plurality of marks MK still recognized,
Adjacent 1 recognized prior to recognition of the mark MK
This is a recognition method for recognizing the mark MK by referring to one or more marks.

An apparatus 2 according to a fifth aspect of the present invention recognizes the mark MK based only on the zone in which the pattern PT can be identified, and outputs the one or more recognized marks MK. Has a transition table TT indicating the correspondence between the mark recognized in step S1 and the mark MK expected in this time, and a register 16 for storing the mark recognized in the past, and the inference unit 13 recognizes a plurality of marks. At this time, the mark MK is recognized by referring to the transition table TT based on the past mark stored in the register 16.

[0018]

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

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

[0020]

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,
Among the mark recognition ROM 12 that recognizes a mark based on all the identification codes DCD output from the pattern identification ROMs 11a to 11f and the identification code DCD output from the pattern identification ROMs 11a to 11f, the identification code DCD capable of pattern identification It comprises an inference ROM 13 which infers a mark based only on the format, a format monitoring unit 14, a mark transition ROM 15, and a register 16.

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

Here, the TONE signal is a signal which is set by detecting the TONE pattern and reset when the peak pulse in NRZ1 [non-zero return (1) recording] is continuously present in 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 that is reset by detecting the peak pulse. Therefore, when the TONE signal is on and the VOID signal is off, the pattern of the track is identified as the TONE pattern, and when both the TONE signal and the VOID signal are off, it 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 VOID signal for the three tracks, and the identification result is 4
It is output as a bit identification code DCD.

In the identification code DCD, the zone is TO
It includes information indicating whether it is identified as the NE pattern or the ALL1 pattern, information indicating the number of tracks in which a read error occurs, and the like.

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

That is, when the threshold value SL is "3", the zone pattern is determined only when the patterns of all three tracks are the same. When the threshold SL is "2", if two or more tracks have the same pattern, the pattern is determined as the zone pattern. When the threshold SL is set to “1”, if the pattern of one track can be identified, even if a read error occurs in the other two tracks,
The identified track pattern is determined as the zone pattern. The value of the threshold 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 (step # 15 in FIG. 2) described later. "1" is set respectively.

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

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

For example, when the two zones A and B are respectively identified as "T" and "1" and the four zones C to F are indistinguishable, the pattern input to the inference ROM 13 is " T1XXXX ”. As a mark in this case, there is a possibility that "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, all 1's.
It is output as 10-bit data configured by allocating each mark to one bit 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 prior to 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. 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
"identity identification" is recorded, and thereafter, "IDS (ID-separato)" is recorded.
r) "" IBG (interblock gap) "
"SPM (special mark merge)
1 ”and the like are recorded.

Further, in the case of 36 tracks, "W" for controlling the return of the magnetic tape TP near the end (EOT) of the magnetic tape TP in the forward (FWD) direction.
"RAP", "SPM3", "IBG", etc. are recorded, and similar marks MK are recorded in the backward (BWD) direction.

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

Therefore, in this embodiment, the transition tables TT1 and TT2 showing 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 are defined in the ANSI standard. Mark transition R created based on the specified tape format
It is stored in the OM 15.

FIG. 3 is a diagram showing a transition table TT1 for the forward direction, and FIG. 4 is a diagram showing a transition table TT2 for the backward direction. For example, according to the transition table TT1 in FIG. 3, “DID” is expected when the mark MK has not been recorded twice in the past. 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 the mark transition ROM 15
1 and TT2 are switched by a reading direction designation signal (F / B). The register 16 stores the 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 above, the current marks MK are predicted based on the contents of the register 16 by referring to the transition tables TT1 and TT2, and the matching marks are recognized and output as the current marks. .

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 obtained.
Pattern P of each zone based on the signal and the VOID signal
Identification of T is performed (# 10). When the mark can be recognized by the mark recognition ROM 12 based on the identified pattern (Yes in # 11), the mark MK
a is output (# 21).

Mark recognition RO because of the error zone
When the recognition by the M12 is impossible (No in # 11), after the error zone is determined (# 12), the inference is performed by the inference ROM 13 and one or more marks MK are output (# 13).

The mark output from the inference ROM 13 is 1
If it is one (Yes in # 14), the mark MK
b is output (# 22). When 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 executed again.
Is performed (# 16), and if there is one mark, the mark MKb is output (# 23).

If there are still a plurality of marks, the mark transition ROM 15 outputs the mark MKc by referring 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 conventional case, but the mark recognition ROM 12 cannot recognize it because of the error zone. In this case, first, the mark MK is tried to be recognized based on the pattern of the zone other than the error zone. If the mark MK is still unrecognizable, the threshold SL is lowered to try to recognize the mark MK. If there is, the mark MK of this time 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, and the error is corrected without performing the retry control and the mark is recognized. Can be done quickly. Also, when used in combination with retry control, the mark recognition rate is improved compared to the conventional case, and in any case, the system reliability is improved.

If the mark recognition ROM 12 cannot recognize the threshold value, the inference ROM 13 is first recognized without immediately lowering the threshold value SL, and the threshold value SL is lowered when a plurality of marks cannot be discriminated. , The decrease in reliability due to the decrease in the threshold value SL can be minimized.
In addition, when there are a plurality of marks output from the inference ROM 13, the transition table TT is referred to select a mark that matches the expected mark of this time, so high reliability is maintained in recognition of the mark. To be done.

In the above embodiment, the inference by the inference ROM 13 and the transition table T by the mark transition ROM 15 are performed.
The reference of T and the lowering of the threshold SL may be applied in an order and combination other than those mentioned above. When lowering the threshold value SL, the threshold value SL may be sequentially lowered such as “3” “2” “1”.

In the above embodiment, the mark recognition ROM
12 may be omitted, and 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 may be shown for each. A table stored in an appropriate external storage device, a RAM to which the table is transferred, a table or program stored in the main storage device, or a hard logic may be used instead of or together with the inference ROM 13 and the mark transition ROM 15. Good. In addition, the configuration of the recognition device 2,
The contents and configuration of each table, the contents or order of the flowcharts, and the like can be variously changed other than those described above in accordance with the gist of the present invention.

[0050]

According to the present invention, when a magnetic tape reading error occurs, the error can be quickly corrected and the mark can be recognized without performing the retry control, thereby improving the system reliability. You can

According to the invention of claim 2, the mark recognition rate is further improved. According to the inventions of claims 3 and 4, the mark recognition rate is further improved.

[Brief description of 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 a recognition device.

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

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

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

FIG. 6 is a diagram showing an example of marks 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 a correspondence relationship between tracks and zones of 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 part) 16 register PT pattern MK mark SL threshold TT transition table

Claims (5)

[Claims] 1. A pattern (P) of a plurality of zones each consisting of a group of a plurality of tracks, based on track data read from each track of a magnetic tape.
T) is respectively identified, and the mark (MK) is recognized based on the pattern (PT) of each identified zone, which can be identified when there is a zone in which the pattern (PT) cannot be identified. A method of recognizing a mark pattern on a magnetic tape, characterized by recognizing a mark (MK) based on only a zone. 2. A pattern (P) of a plurality of zones each made up of a group of a plurality of tracks based on track data read from each track of the magnetic tape.
T) is respectively identified, and the mark (MK) is recognized based on the pattern (PT) of each identified zone, which can be identified when there is a zone in which the pattern (PT) cannot be identified. The mark (MK) is recognized based on only the zones, and when there are a plurality of marks (MK) to be recognized, the threshold (SL) for pattern identification in the unidentifiable zone is lowered to enable the identification. A method for recognizing a mark on a magnetic tape, wherein the mark (MK) is recognized by increasing the number of zones. 3. A pattern (P) of a plurality of zones each made up of a group of a plurality of tracks, based on track data read from each track of a magnetic tape.
T) is respectively identified, and the mark (MK) is recognized based on the pattern (PT) of each identified zone, which can be identified when there is a zone in which the pattern (PT) cannot be identified. The mark (MK) is recognized based on only the zone, and when there are a plurality of marks (MK) to be recognized, one or more adjacent marks recognized prior to the recognition of the mark (MK). Is used to recognize the mark (MK), the mark recognition method on the magnetic tape. 4. A pattern (P) of a plurality of zones each consisting of a group of a plurality of tracks, based on track data read from each track of a magnetic tape.
T) is respectively identified, and the mark (MK) is recognized based on the pattern (PT) of each identified zone, which can be identified when there is a zone in which the pattern (PT) cannot be identified. The mark (MK) is recognized based on only the zones, and when there are a plurality of recognized marks (MK), the threshold (SL) for pattern recognition in the unrecognizable zone is lowered to recognize the mark (MK). When there are a plurality of marks (MK) that are associated with each other, the mark (MK) is recognized by referring to one or more adjacent marks recognized prior to the recognition of the mark (MK). Mark recognition method on magnetic tape. 5. A pattern (P) of a plurality of zones each made up of a group of a plurality of tracks, based on track data read from each track of a magnetic tape.
A device (2) for recognizing a mark (MK) on the basis of a pattern (PT) of each identified zone, and a mark based on only a zone in which the pattern (PT) can be identified. An inference unit (13) that recognizes (MK) and outputs one or more recognized marks (MK), a mark recognized in the past and a mark (M
Transition table (TT) showing the correspondence with K), and a register (16) for storing marks recognized in the past.
When a plurality of marks are recognized by the inference unit (13), the marks () are referred to by referring to the transition table (TT) based on the past marks stored in the register (16). MK) recognition device for recognizing marks on a magnetic tape.