JP2004253097A - Magnetic tape device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce quantity of pull-in data and a pull-in time required for phase adjustment in read-out of data by generating a reference clock for write-in/read-out based on information of a servo region. <P>SOLUTION: In a magnetic tape device performing write-in/read-out of data for a magnetic tape having a servo region being continuous in the direction of length of a magnetic tape, a reference clock is generated based on information of the servo region in which write-in is performed earlier than a data region, write-in of data is performed by this reference clock.In read-out of data, the reference clock is delayed based on a read-data pulse, and a discrimination clock for read-out of data is generated. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic tape device, and more particularly to a phase synchronization technique for reducing the amount of data to be drawn in and the time required for reading data in the magnetic tape device.
[0002]
[Prior art]
In recent years, there has been a demand for improving the data read efficiency of a magnetic tape device, and it has become an important issue how to reduce the pull-in time during data read.
[0003]
Conventionally, the operation of a phase adjustment circuit (PLL) of a magnetic tape device is synchronized with a reference oscillator (a clock directly connected to a crystal oscillator or the like or a frequency obtained by dividing the reference oscillator) until read data is input. This is performed at the output timing of the reference oscillator. On the other hand, at the time of data reading, phase adjustment is started by switching the input from the output of the reference oscillator to the read data (for example, Patent Document 1: FIG. 5). In this phase adjustment, the read data is pulled in, the phase difference from the oscillator output is detected, and the control voltage is adjusted so that the oscillator output follows the read data pulse. Considering the variation of the phase difference, the response time constant, and the like, at least several tens of read pulse data are required after the start of read data read.
[0004]
In the invention according to Patent Document 1, in the read mode, the output signal of the voltage controlled oscillator follows the read data pulse, and the phase of the reference clock is synchronized with the output of the voltage controlled oscillator. The transient response generated in the control voltage generation circuit at the time of switching is suppressed. Thus, when switching to the next read mode, the influence on the response characteristics of the control voltage generation circuit is reduced, and the pull-in response time of the phase locked loop is shortened.
[0005]
Patent Document 2 also discloses a phase synchronization technique for shortening the pull-in time. Also in this technique, a reproduced clock is generated by causing the output of a VCO (voltage controlled oscillator) to follow a read data pulse.
[0006]
[Patent Document 1]
JP-A-5-166293 [Patent Document 2]
JP-A-5-62366
[Problems to be solved by the invention]
In the related art in which the output of the voltage controlled oscillator follows the pulse signal obtained from the read data at the time of data reading, as described above, a sync pattern area of several tens of data pulses is required until the synchronization adjustment is completed. Time was required. Further, in the invention of Patent Document 1, since the frequency of the reference clock is maintained until the next read mode, the phase may be largely shifted due to a fluctuation component such as a tape slip during that time. For the phase adjustment, the same sync pattern area and pull-in time as above are required.
[0008]
Furthermore, in the read operation of the magnetic tape device, first, when the tape speed falls within a predetermined reference value, servo information is read and head positioning control is performed. When this positioning is completed, read data is read and read data pulses are read. Is extracted, and the above-described phase adjustment is started. Since the phase adjustment of the conventional device relies only on read data read after the positioning is completed, there is a limit in shortening the pull-in time.
[0009]
The present invention has been made in view of the above problems, and aims to reduce a read data pulse or pull-in time required for phase adjustment at the time of data reading by generating a reference clock for writing / reading based on information in a servo area. With the goal.
[0010]
[Means for Solving the Problems]
In order to achieve this object, the present invention provides a magnetic tape having a servo area which is continuous in the length direction of the tape, and reads information in the servo area before writing / reading to / from a data area to read data from the servo area. In a magnetic tape device for performing positioning, a reference clock generating circuit for generating a reference clock based on information of the servo area when writing / reading to / from a magnetic tape is provided, and based on the reference clock, magnetic recording to the magnetic tape is performed. It is characterized by comprising a discrimination clock generating means for writing data to a tape and for generating a discrimination clock for reading data by delaying the reference clock based on read data at the time of reading data. When the running speed of the magnetic tape is within a reference value, the reference clock generation circuit adjusts the reference clock as needed based on the information of the servo area.
[0011]
In this magnetic tape device, the write data is synchronized with the servo information, and the reference clock at the time of reading the data is also synchronized with the clock at the time of writing. Only the phase difference need be compensated. This phase compensation can be completed with the first few pulse data at the start of data reading. Therefore, the amount of pull-in data and the pull-in time required at the time of reading can be reduced.
[0012]
It is effective that the discrimination clock generation means includes a phase comparison circuit that performs a phase comparison between the reference clock and the read data pulse, and a delay processing unit that delays the reference clock based on an output of the phase comparison circuit. is there.
[0013]
The delay processing unit may include three delay circuits each capable of delaying a phase up to 180 degrees, and an appropriate delay within a range of 90 degrees to 450 degrees with respect to the phase of the reference clock based on an output of the phase comparison circuit. It is effective to provide an arithmetic circuit for setting an appropriate amount of phase delay in the three delay circuits.
[0014]
On the other hand, a control method of a magnetic tape device according to the present invention is a control method of a magnetic tape device for reading / writing data from / on a magnetic tape having a servo area continuous in the length direction of the tape. A reference clock is generated based on information of the servo area of the magnetic tape read at the time of writing, and at the time of data writing, writing is performed at the timing of the reference clock, and at the time of data reading, the reference clock is generated based on a read data pulse read from the magnetic tape. The present invention is characterized in that a clock is delayed to generate a discrimination clock for reading data. In this method, when the running speed of the magnetic tape is within a reference value, the reference clock is adjusted as needed based on the information of the servo area.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of a magnetic tape device according to the present invention. Referring to FIG. 1, this magnetic tape device 1 is connected to a host device 3 and writes / reads data to / from a magnetic tape 5 at the request of the host device 3. The running direction and speed of the magnetic tape 5 and other internal operations of the magnetic tape device 1 are controlled by the control unit 7. The exchange of data and other control signals a with the host device 3 is performed via the I / O 7.
[0016]
FIG. 2 is a diagram schematically illustrating the configuration of the magnetic tape 5. The magnetic tape 5 has 128 data tracks, and the data tracks are divided into four track groups (groups # 1 to # 4) every 32 tracks. Servo areas (areas A to E) are provided on both sides of each track group. Servo information is recorded at predetermined intervals in the servo area, and each servo information includes a servo mark indicating a start position, servo data indicating a position in a tape length direction, and a burst pattern used for position adjustment of a magnetic head. Included (not shown). Note that an edge protection band is provided at the edge of the tape.
[0017]
In FIG. 1, the transducer 11 includes a write head, a read head, a servo head, and a sensor for detecting a position control range (not shown). When the tape is driven, the servo information of the magnetic tape is read by the servo head, and is input to the mark / data / position detection circuit 15 via the servo reading circuit 13. The mark data / position detection circuit 15 detects the servo mark, servo data, and the amount of displacement of the transducer by burst pattern analysis. The output of the circuit 15 is sent to the control unit 9 and the position error detection controller 17.
[0018]
On the other hand, the sensor output of the transducer 11 is sent to a transducer limit detector 19, which sends a limit detection signal b to the positioning actuator 21, the position error detection controller 17, and the control unit 9. The position error detection controller 17 sends an actuator to the positioning actuator 21 based on the basic position information from the control unit 9, the position information from the mark / data / position detection circuit 15, and the limit detection signal b from the transducer limit detector 19. Sends control signal c. As a result, the positioning actuator 21 adjusts the position of the transducer 11, and positioning in the track direction is performed.
[0019]
The output of the servo read circuit 13 is also input to the reference clock generation circuit 23. The reference clock generation circuit 23 generates and outputs a reference clock d for data writing / reading in accordance with a detection interval of a servo mark which is continuously input while the magnetic tape is running. This clock d is sent to the read / write circuit 25 and used as a reference clock at the time of writing and reading.
[0020]
The read / write circuit 25 receives write data from the control unit 9, writes data on the magnetic tape 5 from the write head of the transducer 11, and sends data read by the read head of the transducer 11 to the control unit 9. At the time of data writing, the read / write circuit 25 performs writing with the reference clock d output from the reference clock generation circuit 23. Since this reference clock is generated from servo information, the written data is synchronized with the servo information. I have. Also, when reading data, a reference clock generated from the same servo information is used. However, since a phase shift occurs due to the positional relationship between the write head and the read head, it is necessary to perform phase adjustment.
[0021]
FIG. 3 is a diagram for explaining a configuration of a read circuit portion of the read / write circuit 25 as an embodiment of the present invention. The output of the read head mounted on the transducer 11 is amplified to a constant amplitude by the AGC 27, then shaped by the filter 29, and pulsed by the pulse qualifier 31. The read data pulse e is sent to the signal processing unit 33 and the phase comparison circuit 35. The signal processing unit 33 identifies the pattern of the input pulse data e, and sends a read gate signal f to the phase comparison circuit 35 and the delay processing unit 39 when recognizing that it is a data area. The phase comparison circuit 35 receives the read data pulse e, the read gate signal f, and the output clock of the delay processing unit 37 as input signals, and compares the phase of the read data pulse e with the output clock of the delay processing unit 37 when the read gate signal f is input. Then, the phase information is sent to the delay processing unit 37. The delay processing unit 37 determines the amount of delay based on the phase information from the comparison circuit 35, delays the output of the reference clock generation circuit 23, and sends it to the signal processing unit 33 as a discrimination clock for read data.
[0022]
FIG. 4 is a detailed diagram illustrating the configuration of the delay processing unit 37. As shown in FIG. 4, the delay processing section 37 includes three delay circuits 38A to 38C, an arithmetic circuit 39 for setting the delay amounts of these delay circuits, and a pulse width adjustment circuit 41. Each of the delay circuits 38A to 38C enables a phase delay of 180 degrees, and can delay the phase of the output clock of the reference clock generation circuit 23 by 540 degrees or more in total. The arithmetic circuit 39 sets the phase information closest to the phase of the output clock of the reference clock generation circuit 23 within the range of 90 degrees to 450 degrees to the delay circuits 38A to 38C based on the phase information sent from the phase comparison circuit 35. I do. The pulse width adjustment circuit 41 adjusts the output pulse width of the delay processing section 39 to be constant.
[0023]
The operation of the magnetic tape device 1 thus configured will be described below. Based on a control signal from the host device 3, the control unit 9 executes the running control of the magnetic tape 5 and the positioning operation of the head for writing or reading data. In this operation, when the running speed of the magnetic tape 5 falls within the reference value, the servo reading circuit 13 is started, and the output thereof positions the magnetic head to a predetermined physical track.
[0024]
In parallel with this positioning operation, the reference clock generation circuit 23 generates a reference clock d corresponding to the tape speed based on the output of the servo reading circuit 13. When writing data, the read / write circuit 25 writes data to the magnetic tape 5 according to the reference clock d. When the control unit 9 reads data on the magnetic tape, the read circuit shown in FIG. 3 generates pulsed read data e and a discrimination clock, and performs data reading with the discrimination clock. Here, the output clock of the delay processing unit 37 is fixed at a fixed phase difference with respect to the phase of the reference clock generation circuit 23 until the read gate signal f is input. From this state, the arithmetic circuit 39 shown in FIG. 4 uses the phase information from the phase comparison circuit 35 to convert the phase information closest to the phase of the reference clock within a range of 90 to 450 degrees to the delay circuits A to C. Set to. Thereafter, the arithmetic circuit 39 adjusts the phase within a range of 0 to 540 degrees until the reading operation is stopped.
[0025]
The reason why the phase compensation amount of the delay processing unit 33 is set to 540 degrees or more in the present embodiment is that the phase compensation range is 0 to 360 degrees when the phase amount at the time when the read gate signal is input is 0 degree. In order to further set the phase advance, it is necessary to set a delay amount of about 360 degrees. In this case, the clock phase is rotated 360 degrees, so that a clock omission occurs. Therefore, the delay circuits 38A to 38C are each provided with a delay amount of 180 degrees, and the total phase compensation range is set to 0 to 540 degrees.
[0026]
【The invention's effect】
In the magnetic tape device of the present invention, a reference clock is first generated based on servo information read at the time of a write / read operation on a magnetic tape, and data is written / read using the reference clock. In this magnetic tape device, the write data is synchronized with the servo information, and the reference clock at the time of reading the data is also synchronized with the clock at the time of writing. Only the phase difference need be compensated. This phase compensation can be completed with the first few pulse data at the start of data reading. Here, the reference clock is generated at the positioning stage before the read data is read, so that no extra time is required. In addition, since the reference clock corresponds to the tape speed, it has been necessary to consider it at the time of conventional reading. There is no speed fluctuation component of the tape. As described above, the discrimination clock for data reading can be generated earlier, and the amount of data to be drawn in and the pull-in time at the start of reading, which conventionally required several tens of pulse data, can be drastically reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a magnetic tape device according to the present invention.
FIG. 2 is a diagram schematically showing a configuration of a magnetic tape shown in FIG.
FIG. 3 is a diagram showing a configuration of a read circuit portion of the Read / Write circuit shown in FIG.
FIG. 4 is a diagram illustrating a configuration of a delay processing unit illustrated in FIG. 3;
[Explanation of symbols]
REFERENCE SIGNS LIST 1 magnetic tape device 5 magnetic tape 9 control unit 13 servo readout circuit 23 reference clock generation circuit 25 read / write circuit 31 pulse qualifier
33 signal processing unit 35 phase comparison circuit 37 delay processing unit 38 delay circuit 39 arithmetic circuit d reference clock e read data pulse f read gate signal

Claims (6)

A magnetic tape device that reads information of the servo area and performs positioning of a magnetic head before writing / reading to / from a data area for a magnetic tape having a servo area continuous in the length direction of the tape,
A reference clock generation circuit for generating a reference clock based on the information of the servo area when writing / reading to / from the magnetic tape, and writing data to the magnetic tape based on the reference clock;
A magnetic tape device comprising: a discrimination clock generating means for generating a discrimination clock for data reading by delaying the reference clock based on read data at the time of data reading. 2. The magnetic tape device according to claim 1, wherein the reference clock generation circuit adjusts the reference clock as needed based on the information of the servo area when the running speed of the magnetic tape is within a reference value. Magnetic tape device. 3. The magnetic tape device according to claim 1, wherein the discrimination clock generation unit performs a phase comparison between the reference clock and a read data pulse, and generates the reference clock based on an output of the phase comparison circuit. 4. A magnetic tape device, comprising: a delay processing unit for delaying. 4. The magnetic tape device according to claim 3, wherein the delay processing section includes three delay circuits each capable of delaying a phase by up to 180 degrees, and a delay processing section that determines a phase of the reference clock based on an output of the phase comparison circuit. And an arithmetic circuit for setting an appropriate amount of phase delay in the three delay circuits within a range of degrees to 450 degrees. In a control method of a magnetic tape device for reading / writing data to / from a magnetic tape having a servo area continuous in the length direction of the tape, a method for controlling a magnetic tape device based on information of a servo area of the magnetic tape which is read at the time of positioning a magnetic head. A reference clock is generated, and at the time of data writing, writing is performed at the timing of the reference clock, and at the time of data reading, the reference clock is delayed based on a read data pulse read from the magnetic tape to generate a discrimination clock for data reading. A method for controlling a magnetic tape device. 6. The magnetic tape device control method according to claim 5, wherein the reference clock is adjusted as needed based on information in the servo area when the running speed of the magnetic tape is within a reference value. Control method.

Images