JP4098437B2 - Method and apparatus for correcting gap deviation of magnetic tape - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gap deviation correction method and a correction apparatus for a magnetic tape in a magnetic tape apparatus.
[0002]
When recording and reproducing digital signals on a magnetic tape device, an IBG (Inter Block Gap) is provided between the data blocks, and when writing other data on the recorded magnetic tape, the magnetic tape When the IBG is detected by reading the data, a write control signal is generated. However, the write start position may be accurately deviated from the head position of the data block, and a solution is desired.
[0003]
[Prior art]
FIG. 4 is an explanatory diagram of a conventional example. A. of FIG. In the figure, 80 is a magnetic tape, 81 and 83 are IBGs (Inter Block Gap) provided between data blocks, 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. BOT (Beginning Of Tape) represents the beginning of the tape, and EOT (End Of Tape) represents the end of the tape. The gap-in signal (Gapin) is a signal indicating the start of writing generated from the control circuit 85, and the gap-out signal (Gapout) is a signal indicating the end of the data block generated from the control circuit 85.
[0004]
As a recording format on the magnetic tape, A. of 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 where a specific pattern is repeatedly recorded. Normally, when writing to the magnetic tape 80, a method is generally adopted in which the write head 86b is driven to write data (IBG and data block), and the contents written by the read head 86a are read and checked. Has been.
[0005]
When a 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, when the magnetic tape 80 is read by the read head 86a and a read signal is input to the control circuit 85, the end of the data block 82 before the target data block 84 (before IBG 83) is detected. A gap out signal is generated from the control circuit 85. Based on the information indicating this position, a gap-in signal for starting writing is generated from the circuit for controlling the drive of the tape of the control circuit 85, and writing (writing of a new IBG and a new data block) is immediately performed by this signal. Be started. However, there is a case where writing is performed after the tape is idle-fed for a set time of the idle timer (for example, 0.4 ms) after the gap-in signal.
[0006]
[Problems to be solved by the invention]
When new data is overwritten on the recorded data on the magnetic tape described above, the read head detects the end of the data block and generates a gap-out signal. Signal) is generated, but when the gap-in signal is generated, the position of the write head is often greatly shifted due to the tension or slip of the tape.
[0007]
That is, when the gap-in signal is generated, the writing head may be shifted to (1) side (EOT side) and may be shifted to (2) side (BOT side). Shows the state of writing in that case.
[0008]
If the gap-in signal shifts to the (1) side (EOT side), B. of FIG. As shown in (1), a new IBG is written on the original IBG, so that the IBG looks long. If it is shifted to (2), B. of FIG. As shown in (2), the previous data (data block 82) is deleted by IBG.
[0009]
In the case of (1) above, the IBG just looks long and does not cause a big problem. However, in the case of (2), the fact that the data has been erased is discovered for the first time by performing the data reading operation by the read head after erasing. And when it is found, it is after it is erased, and the lost data cannot be reproduced.
[0010]
The present invention relates to a magnetic tape apparatus for detecting gap deviation that may erase data of a previous block by writing IBG and correcting the deviation when adding data to a magnetic tape on which data is recorded. An object of the present invention is to provide a magnetic tape gap deviation correction method and correction device.
[0011]
[Means for Solving the Problems]
FIG. 1 is a diagram illustrating the principle of the present invention. In FIG. Is the principle configuration. Is the relationship between the magnetic tape position and each signal. Indicates the function of the idle timer.
[0012]
A. of FIG. 1 is a drive control circuit to which a read signal is input and a write signal is output by being connected to a read head or a write head, 2 is an IBG (Inter Block Gap) detection circuit, 3 is a misalignment measuring circuit, and 4 is This is a misalignment correction circuit. In FIG. , 5 is a magnetic tape, 6-1 and 6-2 represent IBG, and 7 ', 7-1 and 7-2 represent data blocks.
[0013]
When it is desired to overwrite data on the magnetic tape 5, for example, data including IBG6-2 and data block 7-2, the leading position of data (IBG6-1, data block 7-1) recorded before the data In FIG. 4, the read head (not shown) detects the end of the immediately preceding data 7 'and generates a gap-in signal from the drive control circuit 1. In the present invention, since this gap-in signal is based on reading data one block before the original write position, it is referred to as a read gap-in signal (represented by RGApin). This signal is input to the misalignment measuring circuit 3. The read gap-in signal is the same as the conventional gap-in signal as shown in B. of FIG. 1 indicating the head position of the next data (IBG6-1). It occurs at the timing of (1).
[0014]
After this signal is generated, an operation for detecting a specific pattern representing IBG from the read signal of the magnetic tape 5 by the IBG detection circuit 2 is performed. When the specific pattern is detected at the timing represented by (2), the detection signal is supplied to the misalignment measuring circuit 3. The positional deviation measuring circuit 3 receives a positional deviation value (xms () from the input of the read gap-in signal (1) to the actually recorded IBG position (corresponding to the timing (2) of B. in FIG. 1). (Measured in milliseconds)). The measured misregistration value is supplied to the misregistration correction circuit 4 as a correction value (xms). When the magnetic tape 5 moves and the end of the data block 7-1 one block before is detected by the read head, a gap-in signal indicating the start position of data to be written is generated. In the present invention, this signal is called a write gap-in signal (represented by WGApin), and this signal is supplied to the misalignment correction circuit 4. When this write gap in signal (WGapin) is detected, the misregistration correction circuit 4 takes the timing of the correction value (xms) input from the misregistration measurement circuit 4 and corrects when the timing elapses. Generates a write gap-in signal (displayed with Cor-WGapin). Write data (a specific pattern having a predetermined length representing IBG and overwrite data) is output from the drive control circuit 1 to the write head at the timing of the corrected write gap-in signal, and writing is executed. The misalignment correction circuit 4 compares the correction value (xms) from the misalignment measurement circuit 3 with a preset threshold value and exceeds the threshold value, and generates a misalignment error signal indicating that the correction is impossible.
[0015]
As described above, after reading the previous data and generating the gap-in signal (the read gap-in signal (1) of B. in FIG. 1), the time for actually detecting the IBG (in the B. of FIG. 1). The positional deviation value (xms) up to (2)) is also corrected for the positional deviation (IBG and data block) immediately after that because there is a high probability that IBG is recorded. By generating the corrected write gap-in signal, it is possible to solve the problem of erasing data recorded before data to be added.
[0016]
In addition to the method described above, correction values measured by the misregistration measurement circuit 3 are collected as log information, and when a tendency that the magnetic tape is always shifted to the BOT side (IBG comes earlier) is detected, FIG. C. As shown in the outline, after the write gap in signal (WGapin) is generated, the time of the idle timer (the time to idle the tape without writing) is set to the normal time It is possible to use a method in which the magnetic tape is idled longer than the time for which the gap is guaranteed, 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 may be guaranteed by recording the IBG length longer.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 shows the configuration of an embodiment of the present invention.
[0018]
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 controller composed of firmware. . In addition, 110 to 112 and 114 in the reading circuit 11 correspond to the respective parts represented by reference numerals 2 to 5 in FIG. 1, 110 is an IBG detection circuit, and 111 is a case of adding (overwriting original data). In order to confirm the end position of the data to be overwritten, the gap-out generation circuit generates a gap-out signal (Gapout) by detecting a signal representing the end position of the target data once read. Reference numeral 112 denotes a positional deviation correction circuit, reference numeral 114 denotes a positional deviation correction circuit, and reference numeral 113 denotes an IBG length measurement circuit that measures the length of the IBG. Reference numeral 115 denotes a log data collection circuit including a storage area 115a for log data of a correction value (deviation amount) when shifted to the BOT side and a storage area 115b for log data of a shift amount when shifted to the EOT side, 116 Is a sequencer that controls the sequence operation of each unit in the reading circuit 11. Further, 12 is a write format circuit for generating IBG and write data for data blocks, and 13 is a controller connected to a host such as a computer and configured by firmware.
[0019]
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.
[0020]
When the controller 13 is activated by a command from the host (not shown), the controller 13 activates the sequencer 116 of the reading circuit 11 to start 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 writing, when the data to be written is read in order to confirm the end position of the data block to be written, a gap is generated based on the signal from the read head. The out generation circuit 111 is driven to generate a gap out signal. The drive control circuit 1 stores this time position by this signal. Further, a read gap-in signal (R-Gapin) is generated from the drive control circuit 10 by detecting the end position of the previous data block by the read head (S2 in FIG. 3), and this is supplied to the misalignment measuring circuit 112. Measurement of misalignment is started (S3).
[0021]
Subsequently, when a read signal input from the read head is supplied to the drive control circuit 10, a peak pulse train (indicated by PKPLS) of the read signal (analog signal waveform) is supplied to the IBG detection circuit 110. The IBG detection circuit 110 performs an operation of detecting a specific bit pattern representing the IBG, that is, a repetition of the pattern “1000000001” (S4 in FIG. 3), and when a specific pattern is detected, an IBG detection signal (indicated by DIBG) Is output to the positional deviation measuring circuit 112. As a result, a positional deviation measurement value (correction value) between the lead gap-in signal and IBG is supplied to the positional deviation correction circuit 114. The positional deviation amount (time value) measured by the positional deviation measurement circuit 112 is a value when the IBG is shifted to the BOT side of the magnetic tape. This measured value is also supplied to the log data collection circuit 115 and set in the storage area 15a (S5 in FIG. 3).
[0022]
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 preceding the target data from the read head. It is assumed that this write gap-in signal is corrected for the time position based on the gap between the read head and the write head (the interval between the R / W heads, for example, 3.95 mm).
[0023]
The misalignment correction circuit 114 determines whether or not a write gap-in signal (indicated by WGApin) has been generated from the drive control circuit 10 (S6 in FIG. 3). The timing is measured by the time length (S7 in FIG. 3), and a corrected write gap-in signal (displayed by CoWGapin representing Correct Gapin) is issued with a time delay of the shift correction value (S8 in FIG. 3).
[0024]
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 value (a value that can be corrected or a boundary value of a value that cannot be corrected) supplied from the controller 13. When it exceeds, a deviation error signal (err) is output. When this error signal is notified to the controller 13, the processing is stopped.
[0025]
The IBG detection output from the IBG detection circuit 110 is also supplied to the IBG length measurement circuit 113, where the time length during which IBG is continuously detected is measured. The IBG length measured here represents the amount of displacement when the displacement 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 for determination.
[0026]
When the correction of the positional deviation is realized by a fixed length (for example, 0.4 ms) from the controller 13 by an idle feed (tape is sent without writing), the IBG length is a normal length ( If it is shorter than about 2 ms), it can be dealt with by increasing the timer value of the idle timer (for example, 0.5 ms).
[0027]
The log information stored in the log data collection circuit 115a has a tendency that the write gap-in signal (WGapin) comes earlier by recording the correction including the case where the correction value is small (when correction is not necessary). Can be detected by the controller 13 and notified to the host (not shown). When the deviation tends to move toward the BOT side as described above, the predetermined time (eg, 0.4 ms) of the idle timer from the controller 13 to the write format circuit 12 is lengthened (eg, 0.5 ms). can do.
The IBG idling timer (area where there is no actual writing) is made longer, and the IBG length is also corrected to be longer, thereby guaranteeing the regular IBG length.
[0028]
【The invention's effect】
According to the present invention, when data is written to a recorded magnetic tape of a magnetic tape device from the middle, it is possible to detect and prevent data destruction due to gap deviation in advance. Also, by collecting and recording log data such as deviation correction values, it is possible to always grasp the state of gap deviation.
[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 example.
FIG. 3 is a diagram illustrating 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)

In a magnetic tape gap deviation correction method in which an inter-block gap (IBG) representing data blocks and data blocks are alternately recorded on the magnetic tape, and one block is read before writing.
Separately generate a read gap-in signal indicating the read start position of the data one block before and a write gap-in signal indicating the write start position of the target data,
The positional deviation value from the lead gap in signal to the generation of the IBG detection signal one block before is measured,
When a write gap-in signal indicating a writing start position of data to be written is generated, a corrected write gap-in signal is output with a delay by the measured displacement value,
2. A method of correcting gap deviation of a magnetic tape, wherein writing of target data is started by the corrected write gap-in signal. In a magnetic tape gap deviation correction method in which an interblock gap (IBG) representing data blocks and data blocks are alternately recorded on the magnetic tape, and one block is read before writing.
Separately generate a read gap-in signal indicating the read start position of the data one block before and a write gap-in signal indicating the write start position of the target data,
Measure the displacement value from the lead gap in signal to the generation of the IBG detection signal one block before,
Collect the measured displacement value as log data,
A gap deviation correction method for a magnetic tape, comprising: starting writing after the magnetic tape is idled for a predetermined time or more when the positional deviation is always at the start side of the magnetic tape according to the collected log data. In a magnetic tape gap deviation correction device in which an inter block gap (IBG) representing data blocks and data blocks are alternately recorded on the magnetic tape and read 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 one block before and a write gap-in signal indicating a write start position of target data, and an IBG pattern from the read signal An IBG detection circuit for detecting a signal, a circuit for measuring a positional deviation from the generation of the read gap-in signal to the generation of a detection signal from the IBG detection circuit, and the measured positional deviation value as a correction value. A position correction circuit that generates a corrected write gap-in signal by shifting the time by the position shift correction value after the write gap-in signal is generated,
2. A magnetic tape gap deviation correcting apparatus, which starts writing target data based on the corrected write gap-in signal. In claim 3,
An IBG length measurement circuit that receives the output of the IBG detection circuit and measures the length of the IBG, and a log data collection circuit that periodically stores the measurement value of the IBG length measurement circuit and the correction value of the displacement measurement circuit A gap deviation correcting device for a magnetic tape, comprising:

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