JP2000285407A - Correction method and correcting apparatus for gap deviation of magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent data recorded before data to be additionally written from being erased by writing with a timing of a correction write gap in signal by which correction is made with a timing by a correction value time. SOLUTION: When detecting generation of a write gap in signal from a drive control circuit 10, a positional deviation correction circuit 114 measures a timing for a time length of a deviation correction value from a time of the generation and, issues the write gap in signal with a time delay of the deviation correction value. Upon receiving the signal, a write format circuit 12 outputs write data (an IBG pattern and write data). The positional deviation correction circuit 114 corrects when the correction value is not over a correction requirement threshold supplied from a controller 13. When the positional deviation is to be corrected by a constant length from an idle timer sent from the controller 13, it can be met by increasing a timer value of the idle timer if an IBG length detected is shorter than a normal length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for correcting a gap deviation of a magnetic tape in a magnetic tape device.

When a digital signal is recorded / reproduced on a magnetic tape device, an I / O signal is inserted between data blocks.
A BG (Inter Block Gap) is provided, and when another data is written on a recorded magnetic tape, a write control signal is generated when the magnetic tape is read and an IBG is detected. In some cases, the write start position is deviated from the head position of the data block accurately, and it is desired to solve the problem.

[0003]

2. Description of the Related Art FIG. 4 is an explanatory view of a conventional example. A. of FIG. Denotes a configuration, in which 80 denotes a magnetic tape, 81, 8
3 is an IBG (Inter Bloc) provided between data blocks.
k Gap), 82 and 84 are data blocks, 85 is a write / read control circuit, 86 is a head, 86a is a read head, and 86b is a write head. In addition, BOT (Beginn
ing Of Tape) indicates the beginning of the tape, and EOT (End Of Tape) indicates the end of the tape. The gap-in signal (Gapin) is a signal generated from the control circuit 85 and indicating the start of writing, and the gap-out signal (Gapout) is a signal generated from the control circuit 85 and indicating the end of the data block.

As a recording format on a magnetic tape, FIG. As shown in the magnetic tape 80, variable-length data blocks (82, 84, etc.) and IBGs (81, 83, etc.) provided between the data blocks are alternately arranged. The IBG is a fixed-length area in which a specific pattern is repeatedly recorded. Normally, when writing to the magnetic tape 80, a method is generally employed in which the write head 86b is driven to write data (IBG and data blocks), and the written contents are read and checked by the read head 86a. Have been.

When a certain data block on the magnetic tape 80 on which data has already been recorded, for example, the data block 84 becomes unnecessary and another data is written (overwritten),
It is necessary to detect the writing position and control the writing. Specifically, the magnetic tape 8 is read by the read head 86a.
When a 0 is read and a read signal is input to the control circuit 85 to detect the end of the data block 82 before the target data block 84 (before the IBG 83), the control circuit 85 generates a gap-out signal. A gap-in signal for starting writing is generated from a circuit that controls the tape of the control circuit 85 based on the information indicating this position, and the writing (writing of a new IBG and a new data block) is started immediately by this signal. Be started. However, writing may be performed after the tape is idle-fed for a set time (for example, 0.4 ms) of the idle-feed timer after the gap-in signal.

[0006]

In the case where new data is overwritten on the data already recorded on the magnetic tape, the read head detects the end of the data block and generates a gap-out signal. Although the gap-in signal (write start signal) is generated at the timing, when the gap-in signal is generated, the position of the write head often shifts largely due to the tension (tension) or slip (slip) of the tape.

That is, the case where the write head is shifted to the side (EOT side) when the gap-in signal is generated,
(BOT side) in some cases. The state of writing in that case is shown in FIG.

If the gap-in signal shifts to the side (EOT side), the gap-in signal shown in FIG. The new IBG is written on the original IBG as shown in FIG.
BG will look long. In addition, when it is shifted to the side, B. in FIG. As shown in (1), the previous data (data block 82) is erased by the additional IBG.

[0009] In the above case, the IBG simply looks long, and does not pose a particular problem. However, in this case, the fact that the data has been erased can be first discovered by performing a data reading operation by the read head after the data has been erased. Then, when it can be found, it is after it has been erased, and the lost data cannot be reproduced.

According to the present invention, when data is additionally written on a magnetic tape on which data is recorded, a gap shift which may erase data of a previous block by writing IBG is detected and the gap is corrected. An object of the present invention is to provide a method and a device for correcting a gap deviation of a magnetic tape in a tape device.

[0011]

FIG. 1 is a diagram illustrating the principle of the present invention. In FIG. Is the principle configuration. Indicates the relationship between the position of the magnetic tape and each signal; Indicates the function of the idle transport timer.

FIG. In the figure, reference numeral 1 denotes a drive control circuit which is connected to a read head or a write head and receives a read signal and outputs a write signal.
A BG (Inter Block Gap) detection circuit, 3 is a displacement measurement circuit, and 4 is a displacement correction circuit. In addition, FIG. , 5 is a magnetic tape, 6-1, 6-2, etc. are I
BG, and 7 ', 7-1, 7-2, etc., represent data blocks.

Some data on the magnetic tape 5, for example, IBG
When it is desired to overwrite data including the data 6-2 and the data block 7-2 with a read head (not shown) at the head position of the data (IBG6-1, data block 7-1) recorded before the data. The drive control circuit 1 generates a gap-in signal by detecting the end of the data 7 'immediately before. In the present invention, this gap-in signal is called a read gap-in signal (indicated by RGapin) because it is based on reading of data one block before the original write position. This signal is input to the displacement measuring circuit 3. The read gap-in signal is the same as the conventional gap-in signal, and indicates the head position of the next data (IBG6-1) in FIG. Occurs at the timing of

After this signal is generated, a specific pattern representing the IBG is read from the read signal of the magnetic tape 5 to the IBG.
The operation of detection by the detection circuit 2 is performed. When a specific pattern is detected at the timing represented by, a detection signal is supplied to the displacement measuring circuit 3. The position shift measuring circuit 3 calculates the position shift value (xms (millisecond)) from the input of the read gap-in signal to the position of the actually recorded IBG (corresponding to the timing B in FIG. 1). Measure). The measured displacement value is supplied to the displacement correction circuit 4 as a correction value (xms). By detecting the end of the data block 7-1 one block before by the movement of the magnetic tape 5 by the read head,
A gap-in signal indicating the start position of the data to be added is generated. This signal is called a write gap-in signal (denoted by WGapin) in the present invention, and this signal is supplied to the displacement correction circuit 4. The displacement correction circuit 4
When this write gap-in signal (WGapin) is detected, the correction value (x
ms) and the corrected write gap-in signal (Cor-WGapin)
). At the timing of the corrected write gap-in signal, write data (a specific pattern of a predetermined length representing IBG and overwrite data) is output from the drive control circuit 1 to the write head, and writing is performed. Further, the position shift correction circuit 4 compares the correction value (xms) from the position shift measurement circuit 3 with a preset threshold value and, when the correction value (xms) exceeds the threshold value, determines that correction is impossible and generates a shift error signal.

As described above, after the previous data is read and the gap-in signal (the read gap-in signal of B in FIG. 1) is generated, the time for actually detecting the IBG (B in FIG. 1). ), There is a high probability that the IBG is similarly recorded for the data (IBG and data block) at the position immediately after that.
By generating a corrected write gap-in signal by correcting only the positional deviation, the problem of erasing data recorded before data to be rewritten can be solved.

In addition to the above-described method, a correction value measured by the displacement measuring circuit 3 is collected as log information, and when a tendency that the magnetic tape always shifts to the BOT side (IBG comes earlier) is detected. , C. of FIG. As shown in outline, after the write gap-in signal (WGapin) is generated, the time of the idle feed timer (time to idle the tape without writing) is usually It is possible to use a method in which the magnetic tape is idle-fed with a longer length than the time required to guarantee the gap, and then a write output is generated to record the IBG (overwrite the IBG of the original magnetic tape) and write the data. At this time, the IBG length may be recorded longer to guarantee the IBG.

[0017]

FIG. 2 shows the configuration of an embodiment of the present invention.

In FIG. 2, 10 is a drive control circuit (corresponding to 1 in FIG. 1) for controlling each driver of the magnetic tape, 11 is a read circuit, 12 is a write format circuit, and 13 is a firmware. It is a controller. Then, 110 to 112 inside the reading circuit 11
And 114 correspond to the parts indicated by reference numerals 2 to 5 in FIG.
Reference numeral 10 denotes an IBG detection circuit, and reference numeral 111 denotes the end position of the data to be read once to confirm the end position of the data to be overwritten when additional writing (overwriting to the original data) is performed. A gap-out generation circuit for detecting a signal and generating a gap-out signal (Gapout). Reference numeral 112 denotes a displacement correction circuit, reference numeral 114 denotes a displacement correction circuit, and reference numeral 113 denotes an IBG length measurement circuit that measures the length of the IBG. A log data collection circuit 115 includes a storage area 115a for storing log data of a correction value (shift amount) when the shift to the BOT side occurs and a storage area 115b for storing the log data of the shift amount when shifting to the EOT side.
A sequencer 16 controls a sequence operation of each unit in the reading circuit 11. Reference numeral 12 denotes a write format circuit for generating write data of the IBG and the data block, and reference numeral 13 denotes a controller connected to a host such as a computer and configured by firmware.

FIG. 3 shows an operation flow of the configuration of the embodiment shown in FIG. 2, and the operation of the configuration of the embodiment of FIG. 2 will be described below with reference to FIG.

When the controller 13 is started by a command from a host (not shown), the controller 13 starts the sequencer 116 of the reading circuit 11 to start the operation (S1 in FIG. 3). At this time, the reading operation of the magnetic tape by the reading head is executed. First, as in the case of normal rewriting, when the data to be rewritten is read to confirm the end position of the data block to be rewritten, the gap is read based on the signal from the read head. The out generating circuit 111 is driven, and a gap out signal is generated. Drive control circuit 1
Stores this time position with this signal. The read head detects the end position of the previous data block and generates a read gap-in signal (R-Gapin) from the drive control circuit 10 (S2 in FIG. 3). The measurement of the displacement is started (S3).

Subsequently, when a read signal input from the read head is supplied to the drive control circuit 10, a peak pulse train (PKPL) of the read signal (analog signal waveform) is obtained.
(Indicated by S) is supplied to the IBG detection circuit 110. IB
The G detection circuit 110 performs an operation of detecting a specific bit pattern representing an IBG, that is, a repetition of a pattern of “100000000001” (S4 in FIG. 3). When the specific pattern is detected, an IBG detection signal (indicated by DIBG)
Is output to the displacement measuring circuit 112. As a result, the measured value (correction value) of the displacement between the read gap-in signal and the IBG is supplied to the displacement correction circuit 114. Note that the displacement amount (time value) measured by the displacement measuring circuit 112 is a value when the IBG is shifted to the BOT side of the magnetic tape. This measurement value is also supplied to the log data collection circuit 115 and set in the storage area 15a (S in FIG. 3).
5).

Thereafter, a write gap-in signal (WGapin) is issued from the drive control circuit 1 in response to detection of the end position of the data block before the target data from the read head. It is assumed that the write gap-in signal has been subjected to time position correction based on the gap between the read head and the write head (the interval between R / W heads, for example, 3.95 mm).

In the displacement correcting circuit 114, a write gap-in signal (WGap
is determined (S6 in FIG. 3), and when the occurrence is detected, the timing is measured by the time length of the shift correction value from the generation time of the write gap-in signal (S7 in FIG. 3), and the shift is determined. A correction write gap-in signal (indicated by CoWGapin representing Correct Gapin) is issued with a delay of the correction value (S8 in FIG. 3).

When the corrected write gap-in signal is supplied to the write format circuit 12, the write format circuit 12 outputs write data (IBG pattern and write data). The drive control circuit 10 converts the write data into a write signal and outputs it to the write head. The misregistration correction circuit 114 determines whether the correction value exceeds a correction necessity threshold (a value that can be corrected or a boundary value of a value that cannot be corrected) supplied from the controller 13, and if not, performs correction. If it exceeds, an error signal (err) is output. When this error signal is notified to the controller 13, the processing is stopped.

The IBG from the IBG detecting circuit 110
Is also supplied to the IBG length measurement circuit 113,
Here, the time length in which the IBG is continuously detected is measured.
The IBG length measured here indicates a shift amount when the position shift is on the EOT side of the magnetic tape, and this measured value is also supplied to the log data collection circuit 115 and set in the storage area 115b. The log data in the storage area 115b is supplied to the controller 13 and determined.

In the case where the correction of the position shift is realized by a constant length (for example, 0.4 ms) idle feeding (for example, sending a tape without writing) from the idle feeding timer from the controller 13, the IBG length is set to a normal value. If it is found that the length is shorter than the length (about 2 ms), the timer value of the idle timer is increased (for example,
0.5 ms).

The log information stored in the log data collection circuit 115a records the correction including the case where the correction value is small (when it is not necessary to perform the correction), so that the write gap-in signal (WGapin) is advanced earlier. When a tendency is observed, the controller 13 can detect this and notify a host (not shown). The displacement is BO
If there is a tendency toward the T side, the time (for example, 0.4 ms) determined by the controller 13 for the idle format timer for the write format circuit 12 is made longer (for example,
0.5 ms). The IBG idle transport timer (the area where there is no actual writing) is set longer and the IB
By correcting the G length to a longer length, a normal IBG length is guaranteed.

[0028]

According to the present invention, it is possible to detect in advance and prevent data from being destroyed due to gap displacement when writing to a recorded magnetic tape of a magnetic tape device from the middle. Further, by collecting and recording log data such as a deviation correction value, the state of the gap deviation can be always grasped.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram illustrating a configuration of an embodiment.

FIG. 3 is a diagram showing an operation flow of the embodiment.

FIG. 4 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive control circuit 2 IBG detection circuit 3 Position shift measurement circuit 4 Position shift correction circuit 5 Magnetic tape 6-1 and 6-2 Data block 7 ', 7-1, 7-2 IBG

Claims (4)

[Claims] An inter-block gap (IBG) representing a data block and a data block are alternately recorded on a magnetic tape, and a gap deviation correction method for a magnetic tape that reads one block before writing is performed before writing.
A read gap-in signal indicating the read start position of the data before the block and a write gap-in signal indicating the write start position of the target data are separately generated. From the read gap-in signal, the IBG of the IBG one block before is generated. A position shift value until the detection signal is generated is measured, and when a write gap-in signal indicating a write start position of data to be written is generated, the write gap corrected by delaying by the measured position shift value. Output in signal,
A method for correcting gap deviation of a magnetic tape, wherein writing of target data is started by the corrected write gap-in signal. 2. A method according to claim 1, wherein an inter-block gap (IBG) representing a data block and a data block are alternately recorded on a magnetic tape, and the data is read one block before writing.
A read gap-in signal indicating the read start position of the data before the block and a write gap-in signal indicating the write start position of the target data are separately generated. From the read gap-in signal, the IBG of the IBG one block before is generated. The position deviation value until the detection signal is generated is measured, and the measured position deviation value is collected as log data. A method for correcting a gap deviation of a magnetic tape, wherein writing is started after the idle feeding for at least a time. 3. An apparatus according to claim 1, wherein an inter-block gap (IBG) representing a data block and a data block are alternately recorded on a magnetic tape, and a gap is corrected by a magnetic tape gap reading apparatus which reads one block before writing.
A drive control circuit for separately generating a read gap-in signal indicating a read start position from a read signal of data before the block and a write gap-in signal indicating a write start position of target data;
An IBG detection circuit for detecting a BG pattern, a circuit for measuring a displacement from the generation of the lead gap-in signal to the generation of a detection signal from the IBG detection circuit, and inputting the measured displacement value as a correction value A position correction circuit for generating a corrected write gap-in signal by shifting the time by the position shift correction value after the generation of the write gap-in signal, and generating a target data based on the corrected write gap-in signal. A gap correction device for a magnetic tape, which starts writing data. 4. The IBG length measuring circuit according to claim 3, wherein an output of said IBG detecting circuit is inputted to measure an IBG length, a measured value of said IBG length measuring circuit, and a correction value of said displacement measuring circuit. A gap data correction device for a magnetic tape, comprising: a log data collection circuit for periodically storing the gap data.