JP3309873B2 - Data storage method 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 for storing data on a magnetic tape, which is preferably applied when a DAT (Digital Audio Tape Recorder) is used as a data recorder.

[0002]

2. Description of the Related Art DAT is a magnetic tape recording / reproducing apparatus for helical scan type audio signals. Recently, this DAT has been used as a data recorder for recording / reproducing data from a computer. .

[0003] When the DAT is used as a data recorder in this manner, data from the host computer is:
Is converted into data having the DAT format,
Recording and reproduction are performed at T.

In the DAT format, two inclined tracks formed on a magnetic tape during one rotation of the rotary drum are formed by two magnetic heads for recording having different azimuth angles attached to the rotary drum. Framed. Then, the 16-bit PCM audio data is
The data is divided into two pieces of 8 bits each, interleaved in units of the frame, and recorded on a tape. Sub data is also recorded on each inclined track.

FIG. 5 shows a track pattern of the DAT. Each inclined track 2 formed on the tape 1 by two recording heads as one frame.
A and 2B are a main area AM for recording PCM audio data and a sub area AS for recording sub data,
Each area is divided. As the sub data, an ATF signal for auto tracking servo, a sub code including a track address as the content, and the like are recorded.

FIG. 6 shows a tape format when DAT is used as a data recorder.

The tape 1 comprises a magnetic tape main body 3 and leader tape sections 4 and 5 made of a transparent material connected to both ends of the main body 3. Although not shown, the tape 1 is stored in a cassette having a supply reel and a take-up reel, and is sequentially transferred from the supply reel to the take-up reel. The start of the magnetic tape main body, which is the connection end between the magnetic tape main body part 3 and the leader tape part 4, on the start end side of the transfer is B
The end of the magnetic tape main body, which is called an OM, and is a connection end between the magnetic tape main body 1 and the leader tape section 5,
Called OM.

[0008] The tape position after a predetermined length from the BOM is the start of a logical tape (called BOT).
The area from BOM to BOT is called a device area 4a, and nothing is recorded or a signal for testing the apparatus is recorded. Subsequent to the device area 4a, a reference area 4d of 35 frames in which a signal indicating the start of data is recorded. Subsequent to the reference area 4d, a history of the number of reading and writing operations, errors, and the like is recorded.
The system area 4e has 15 frames. Next, an area 4f of 23 frames called a vendor group follows the system area 4e. After the vendor group 4f, there are provided a plurality of group areas 4g each consisting of 23 frames in which backup data from the host computer is recorded. At the end of the data,
Data EOD indicating this is recorded for 300 frames.

A tape position that is a predetermined length before the EOM is a logical end of the tape (called LEOT). When the position of this LEOT is detected during data recording, the DAT as a data recorder reports this to the host computer. In response, the host computer recognizes that the physical tape end is near and notifies the user. Then, for example, the user performs data maintenance by exchanging the cassette tape.

Conventionally, at the time of recording, the LEOT tape position is detected by calculating the remaining tape amount every time a predetermined amount of data is written, and based on the obtained remaining tape amount, it is determined whether the LEOT tape position has been reached. Or to decide. As is well known, a method for calculating the remaining tape amount is to provide a supply reel with a frequency generator that generates a frequency signal according to the rotation speed of the supply reel, and measure the cycle of the frequency signal to obtain the tape at that time. The time T of one rotation of the supply reel at the winding diameter is obtained, and the projection area of the tape wound on the supply reel is obtained from this information and the tape thickness information known in advance.

That is, t: tape thickness [mm] l: length of remaining tape [mm] dh: hub diameter of reel [mm] d: tape reel diameter of supply reel at that time [mm], supply reel Area t of the remaining tape winding diameter
1 is tl = π (d / 2) ² −π (dh / 2) ² (1)

Then, the tape speed sent out from the tape supply reel when the remaining amount of the tape is equal to v [mm / se
c], if the remaining time of the tape is z and the time of one rotation of the supply reel is T [sec], l = z · v (2) v = ω · d / 2 = π · d / T (because , Ω = 2π / T) (3) When the above equations (1), (2) and (3) are made simultaneous,
The remaining tape time z can be obtained, and the tape speed v
By dividing this value z, the remaining tape length can be obtained.

[0013]

However, the above-described method for calculating the remaining amount of tape cannot be neglected due to variations in the actual tape thickness t, variations in the reel hub diameter, and other errors. Must have a sufficient margin for detection. Therefore, conventionally, the detection of the logical end LEOT is set so as to be performed earlier as the tape position, and there is a disadvantage that the tape cannot be used effectively.

In the case of the conventional method, the logical end L
The calculation of the remaining tape amount for detecting the EOT must be performed accurately. For this reason, it is necessary to accurately determine the time of one rotation of the supply reel, and it is better to calculate the average of a plurality of rotations of the supply reel.

When the writing of data is temporarily stopped and then started again, it is necessary to perform the same tape running control and mode control as in so-called continuous recording.
At the time of rewriting, rewind the tape by a predetermined amount,
Servo start-up, tracking control, etc. are performed until the end of the previous recording position. In order to accurately determine the one rotation time of the supply reel, the tape is rewound in addition to the predetermined tape amount. Conventionally, it has been necessary to perform tape control. Since this process is performed every time rewriting is started, there is a drawback that the recording time becomes longer by that amount.

In view of the above, the present invention provides a method capable of accurately detecting a logical end LEOT, enabling use of a tape without waste, and shortening a recording time. The purpose is to:

[0017]

In order to solve the above-mentioned problems, the above-mentioned data storage method for tape according to the present invention provides a method of storing data on a magnetic tape while monitoring the remaining amount of the tape by associating reference numerals in the embodiments described later. In a data storage method for writing data to a tape and reporting a logical end of the tape to the host computer when the logical end of the tape is detected, a temporary logical position is set as a tape position before the actual logical end. When the tape position reaches the above-mentioned virtual logical end position, the tape is fast-forwarded to the physical tape end, and the amount of tape from the virtual logical end to the physical tape end is set. , Set a true logical end based on the obtained tape amount, and then return to the tentative logical end position to write data. Performed until the true logical end, in true logical end, characterized in that to perform the end report to the host computer.

[0018]

According to the present invention having the above structure, at the time of recording,
When the rough logical end of tape position is reached, recording is interrupted and the tape is fast-forwarded to the physical end of tape, while the temporary logical end to physical end of tape. Up to the amount of tape required.
From the obtained tape amount, the true logical end tape position is set.

Thereafter, returning to the tape position of the temporary logical end, recording is performed up to the true logical end, and when the true logical end is detected, the fact is reported to the host computer.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a data storage method according to the present invention will be described with reference to the drawings, taking as an example a case where the above-mentioned DAT is used as a data recorder.

FIG. 1 shows an example of a system configuration when a DAT is used as a data recorder.
Is a DAT, 101 is a system bus, 102 is a host computer, and 103 and 104 are local buses.

The DAT 100 is a recording / reproducing mechanical deck 1
1, recording amplifier 12, reproduction amplifier 13, signal processing circuit 1
4, a data buffer RAM 15, a data controller 16, an interface board 17, a system controller 18, a servo and motor drive circuit 19, and the like.

In this example, in the DAT 100, a frequency generator 11FG is provided in the supply reel rotating mechanism in the mechanical deck unit 11. Then, a frequency signal SFG having a frequency proportional to the rotation speed of the supply reel from the frequency generator 11FG is supplied to the servo and motor drive circuit 19 via the waveform shaping circuit 21 and the tape amount and LEOT detection circuit 20 Supplied. The tape amount and LEOT detection circuit 20 can be included in the system controller 18.

The recording / reproducing mechanical deck 11 of the DAT 100
Has a rotating head drum 11D. The magnetic tape 11T is wound around this drum in an angular range of about 90 degrees, and transported by a capstan and a pinch roller (not shown). The drum 11D includes two recording heads having different azimuth angles and two reproducing heads.
During one rotation of 1D, data is recorded as two inclined tracks by two recording heads, and the recorded data is reproduced by two reproducing heads.

At the time of recording, the buses 104, 101, 103
The data transmitted from the host computer to the DAT 100 via the interface board 17 is stored in the RAM 15 via the interface board 17 and the data controller 16.
Then, under the control of the system controller 18, the data in the RAM 15 is sent from the data controller 16 to the signal processing circuit 14, where the data is converted into the DAT format. The converted data is stored in the recording amplifier 12
Is supplied to the recording / reproducing mechanism deck section 11 via a recording head, and is recorded on a magnetic tape by a recording head.

Data recorded on the magnetic tape is reproduced by two reproducing heads and supplied to a signal processing circuit 14 via a reproducing amplifier 13. In the signal processing circuit 14, the data in the DAT format is returned to the original digital data and stored in the RAM 15. The reproduced digital data is transmitted to the data controller 16, the interface board 17, and the buses 103, 101, 1
04 to the host computer 102.

As shown in FIG. 6, data from the host computer 12 is sequentially recorded in a group area 4g consisting of 23 frames. Data from the host computer 102 is recorded as data in the main area of each track.

At the time of recording, every time data is written to the group area 4g, it is checked whether the logical end LEOT of the magnetic tape or the end of the LEOT has been reached by writing the next group area. As a result of the check, if it is detected that the logical end LEOT has been reached or has passed, the system controller 18 reports the fact to the host computer 102 and warns that the tape end is approaching for writing the next data. .

In this case, in the present invention, the tape position of the logical end LEOT is accurately set as described below. That is, in the present invention, a temporary logical end (temporary LEOT (A)) is set in advance. The temporary LEOT (A) is set as a rough tape remaining amount that allows for a sufficient margin with respect to the end EOM of the magnetic tape main body. Since this is a temporary position for determining the true logical end LEOT (C), it may be set roughly as described above. This value can be set, for example, at a position of about 5 m in terms of the length of the remaining tape.

Then, as shown in FIG. 2, at the time of recording,
Each time the data is written to the group area 4g, the remaining tape amount is calculated from the time of one rotation of the supply reel. For this reason, as shown in FIG. 1, a frequency signal SFG proportional to the rotation speed of the supply reel from the waveform shaping circuit 21 is supplied to the cycle detection circuit 22, the cycle of the signal SFG is detected, and the supply is started from the detected cycle. The time T of one rotation of the reel is detected. Signal S
The FG is a signal of, for example, 24 cycles per rotation of the supply reel, and detects the cycle of one rotation by adding 24 cycles of the signal SFG. In order to ensure accuracy, an average is calculated from information on a plurality of rotations of the supply reel.
When it is determined whether or not (A), it is not necessary because the rough may be used.

Information on the detected time T of one rotation of the supply reel is supplied to the remaining tape amount calculating circuit 23, and the remaining tape amount is obtained according to the above-described arithmetic expression. The obtained remaining tape amount is supplied to the temporary LEOT determination circuit 25 through the switch circuit 24, and is compared with the temporary LEOT (A) from the temporary LEOT generation unit (eg, register) 26. Then, the determination circuit 25 determines whether or not the tape position has reached the position of the temporary LEOT (A), and when it has detected that the tape position has reached the temporary LEOT (A), sends a detection signal to the system controller 18. Supply.

The system controller 18 sends the temporary LE
When the OT (A) position detection signal is input, the recording operation is stopped, and the tape is rapidly advanced to the end of the physical tape. At this time, at the tape position of the temporary LEOT (A), the wave number measuring circuit 27 composed of a counter is set by the system controller 18 and the fast-forwarding temporary LEO is set.
Frequency signal SFG from T (A) to end of physical tape
Is measured. The wave number of the measurement result is supplied to the system controller 18. From this wave number, the system controller 18 calculates the tape amount from the temporary LEOT (A) to the end of the physical tape. The tape amount can be either time or tape length, but is calculated as how many frames the tape amount during this time corresponds to. At this time, the leader tape section is excluded.

The system controller 18 sends the temporary LE
Based on the amount of tape from OT (A) to the end of the physical tape, the true LEOT (C) is set as, for example, the remaining amount of tape, and the true LEOT (C) is, for example, a true LEOT generating unit 28 composed of a register. Write to. True LEOT
The tape position in (C) is such that the space between this position and the end of the physical tape satisfies the standard when DAT is used as a data recorder.

Thereafter, the system controller 18 returns to the position of the temporary LEOT (A). The position of the temporary LEOT (A) can be detected from the subcode recorded on the track. When returning to the temporary LEOT (A), the recording is restarted. Upon restarting the recording, the system controller 18 switches the switch circuit 24 to a state opposite to the state shown in the figure.

Then, the cycle detecting circuit 22 determines the time of one rotation of the supply reel again every time data is written in the group area, and the remaining tape amount calculating circuit 23 determines the remaining tape amount. In this case, since the switch circuit 24 has been switched, the information on the obtained tape remaining amount is supplied to the true LEOT determination circuit 29 by the true LEOT generation section 28.
Is compared with the true LEOT (C), and when the next group area is written, it is determined whether or not the tape position of the true LEOT (C) has been passed. When it is detected that the position has passed the true LEOT position, a detection output to that effect is supplied from the determination circuit 29 to the system controller 18.

In response, the system controller 18 reports the LEOT detection to the host computer.

In this case, after the true LEOT (C) is obtained, the switching circuit 2 is not changed until the tape is replaced.
Reference numeral 4 denotes a state in which the state is switched to the determination circuit 29 side.
Fast forward from the position of the temporary LEOT (A),
The time from when the EOT (C) is detected to when the recording returns to the temporary LEOT (A) and resumes recording is about 10 seconds,
Moreover, since the operation of detecting the true LEOT (C) is performed only once for one tape, the overall execution speed is not significantly affected.

FIG. 3 is a flowchart of an example of an operation control routine including the operation of the circuit 20 until the system controller sets true LEOT (C).

This routine 200 is a true LEOT (C)
Before is set, it is called every time the writing of the group area is completed, and the process proceeds from step S1-1 to step S1-2. In step S1-2, the remaining tape amount is obtained from the cycle of the frequency signal SFG proportional to the rotation side of the supply reel, and in the next step S1-3, the tape position is before the temporary LEOT (A) (A). It is determined whether or not. If the result of the determination is that it is before the provisional LEOT (A), this routine is exited from step S1-4. If it is determined that the temporary LEOT (A) has passed, the process proceeds to step S1-5.

In step S1-5, the tape is set to the rewind state. Next, in step S1-6, when it is detected that the end of the tape has been reached, the process proceeds to step S1-7.
The tape amount between the tape position of the temporary LEOT (A) and the end of the physical tape is obtained. Next, in step S1-8, a true LEOT matching the standard is obtained from the obtained tape amount.
(C) The tape position is set.

Next, the flow advances to step S1-9 to rewind the tape. At this time, rewinding is performed while obtaining the subcode from the reproducing head and searching for the tape position. Then, in step S1-10, the tape position is set to the temporary LEO.
When it is detected that the position has reached the position of T (A), the process proceeds to step S1-11 to stop rewinding, and in the next step S1-12, writing of subsequent data is performed using the temporary L.
Restart from EOT (A). Thereafter, this routine 20
Exits 0.

After the true LEOT (C) has been set as described above, the routine 200 shown in FIG. 3 is no longer executed until the tape is replaced, and the routine 300 shown in FIG. Is called and executed each time the writing of the group area 4g is completed.

That is, when this routine 300 is called in step S2-1, step S2-2 is executed.
In step S2-3, when the writing of the next group area 4g is performed, it is determined whether or not the tape position has passed the true LEOT (C). The remaining tape amount can be calculated from the period of the frequency signal SFG proportional to the rotation side of the supply reel. In this case, the temporary LEOT (A) and the true LEOT (C)
Can be recognized as the number of frames, so the number of frames remaining until the true LEOT (C) is determined as the number of frames. If the result of determination is that it is before LEOT (C), step S2
-4, this routine 300 is exited.

On the other hand, if it is determined that the true LEOT (C) has been exceeded, steps S2-3 to S2-5 are performed.
To interrupt the write operation. Then, in the next step S2-6, the fact that the true LEOT (C) of the tape has been detected is reported to the host computer.
This routine 300 is exited from -7.

Although the present invention has been described above by applying the present invention to the case where a DAT is used as a data recorder, the present invention is not limited to this case, and a data recorder for backing up computer data using a magnetic tape is used. It is needless to say that the present invention can be applied to the case of data storage.

[0046]

As described above, according to the present invention, at the time of recording, the provisional LEOT which has been roughly determined is used.
When the tape position of (A) is reached, the tape is fast-forwarded to the end of the physical tape, the tape amount from the temporary LEOT (A) to the end of the physical tape is measured, and the tape position of the true LEOT is determined based on the measured value. Is set, so that the tape can be used without waste.

Then, the position of the true LEOT can be accurately reported to the host computer irrespective of variations in tape thickness and the like.

Further, until the true LEOT is set,
Since it is only necessary to monitor whether or not the tape position of the rough temporary LEOT (A) has been reached, it is not necessary to detect the tape remaining amount as a very accurate value. Therefore, it is not necessary to perform additional rotation, and the recording time as a whole can be shortened accordingly.

[Brief description of the drawings]

FIG. 1 is a block diagram of an example of a DAT data recorder to which a method according to the present invention is applied.

FIG. 2 is a diagram for explaining a method according to the present invention.

FIG. 3 is a flowchart for explaining an example of a main part of the method according to the present invention.

FIG. 4 is a flowchart for explaining an example of a main part of the method according to the present invention.

FIG. 5 is a diagram for explaining a DAT tape pattern.

FIG. 6 is a diagram illustrating a format of a DAT data recorder.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 DAT 101 System bus 102 Host computer 20 Remaining tape and LEOT detecting circuit 25 Temporary LEOT determining circuit 26 Temporary LEOT generating section 28 True LEOT generating section 29 True LEOT determining circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 15/02 364 G06F 3/06 303 G11B 20/10 G11B 27/17

Claims (1)

(57) [Claims] 1. A data storage method for writing data to a magnetic tape while monitoring the remaining amount of a tape and reporting a logical end of the tape to a host computer when the logical end of the tape is detected. A temporary logical end is set in advance as the tape position before the target end, and when the tape position reaches the temporary logical end position, the tape is fast-forwarded to the physical tape end. Calculate the amount of tape from the tentative logical end to the end of the physical tape, set the true logical end based on the obtained tape amount, and then return to the tentative logical end position to write data. To the above-described true logical end, and at the true logical end, report the end to the host computer. Storage method.