JP3160413B2 - Method for calculating recording capacity of magnetic tape device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape device for recording data on a magnetic tape in units of frames by using a rotary head or a fixed head, and more particularly, to a non-recorded area in a remaining area having a data capacity. The present invention relates to a recording capacity calculation method which can be calculated as:

[0002]

2. Description of the Related Art In recent years, a DAT (Digital Audio Tape Recorder) has attracted attention for its large recording capacity, and has been used as a backup recording device such as a hard disk device of a computer. In this type of backup DAT, there are various data recording formats on a tape, and an example is shown in FIG. FIG. 4 shows the entire length of the tape T. Reference numerals 30 and 34 denote areas where the user cannot perform data recording. In the area indicated by reference numeral 30 (section Q1), a certain section from the tape start end (BOM: Bigining Of Media) is an area where the medium is easily damaged during tape loading, and no data is recorded. In a section from this section to a BOT (Bigining Of Tape), management information and the like on the tape are recorded. An area (section Q2) at a predetermined distance from the end of the tape (EOM: End Of Media) is also an area where the user cannot record. Therefore, an area (section U) indicated by reference numeral 35 in FIG. 4 is an area for recording data by the user.

FIG. 4 shows a case where a predetermined amount of data has already been recorded in a plurality of frames in frame units. In a device for DAT, 2
The track is one frame. In FIG. 4, the area indicated by 31 has already been recorded. In this format, when the recording of the recorded area 31 is completed, regular data called EOD (End Of Data) is recorded only for a predetermined section thereafter. This EOD is for searching for the end of the recorded area 31 at the time of next recording. When an EOD is detected by the search operation, the tape is rewound slightly, and data is recorded in the unrecorded area 33 in a state where the EOD is overwritten from the next frame (frame number: Fp) before the EOD. .

[0004]

As means for recognizing the remaining state of the tape in the backup DAT, when the tape advances from the EOM to, for example, about 500 mm before the EOM, the host computer (Earl
Although a warning called "Y Worning" is issued, there is no means for knowing the remaining amount of the tape other than this warning. That is, when data is to be written to unrecorded areas indicated by 32 and 33 in FIG. 4, it is impossible to know in advance whether the amount of data to be recorded falls within the unrecorded area. Therefore, if the data cannot be accommodated at the time when the data is recorded to near the end of the tape, the host computer can recognize the data only after the recording is completed to the vicinity of the end of the tape. It is necessary to replace the recording tape with a new tape.

[0005] Further, some prior arts have proposed that the remaining amount of tape can be recognized as time.
However, this method is effective to some extent when a data group is recognized and managed as time, such as audio information. However, this method is effective when data is managed not as time but as a data amount, such as computer data. is not. Also, when backing up data for a computer, a partition method in which a magnetic tape area is divided into a plurality of areas in advance may be adopted. In this case, the recording area of the tape is divided and divided in advance, and for example, different types of data may be recorded in each divided area. In such a method, even if the remaining amount of tape running can be recognized in time, it is not possible to recognize how many unrecorded areas are present in each divided area.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to make it possible to recognize a recording capacity in an unrecorded area of a magnetic tape as a frame unit or as a data amount.

[0007]

SUMMARY OF THE INVENTION A magnetic tape according to the present invention
The method for calculating the recording capacity of the device is based on the data recorded on the magnetic tape.
1 track for 2 tracks, and tilt the magnetic tape
During one rotation of the magnetic head that slides in the
In a magnetic tape device in which data for a program is written on the magnetic tape, the data is divided into a plurality of loaded magnetic tapes.
The number of frames that can be recorded for each recording area
Each record from the subcode data read from the tape
For each area, the final frame of the already recorded data
System number, and the number of frames in each recording area
Subtract the last frame number, and for each divided recording area
In which the data capacity that can be recorded is calculated.

[0008]

[0009]

In the above means, first, when the magnetic tape is loaded, for example, by detecting the identification of the tape cassette and / or by using the rotation speed ratio of the reel base on the supply side and the winding side, etc.
The total length of the magnetic tape is identified, the tape length that can be recorded by the user is recognized based on, for example, the format shown in FIG. If there is an area that has already been recorded, the last frame number that has already been recorded is detected, and the last frame number that has already been recorded is subtracted from the total number of recordable frames. The number of frames is calculated, and the recordable data amount is recognized.

In this method, since the recording capacity of an unrecorded portion can be recognized, for example, in a method in which the entire length of the tape is divided into a plurality of areas, and data is recorded in each area, each divided area is followed by The amount of data that can be recorded can be determined.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a rotary head type digital audio tape recorder (DAT) for executing the method of the present invention, FIG. 2 is a conceptual diagram showing a recording state of a tape, and FIG. 3 is a flowchart explaining a recording operation. In the digital audio tape recorder (DAT) shown in FIG.
Reference numeral 1 denotes a SCSI bus which is a data transfer path from the host computer. The data to be backed up is transferred by the SCSI bus 1. SCSI
The controller 2 performs protocol control and the like on the data transferred from the host computer, and outputs the control data to the buffer memory 3. The buffer memory 3 temporarily records the transferred data for each predetermined amount.

The ECC circuit 5 is a circuit for error correction, and performs an operation such as adding an error correction code to data stored in the buffer memory 3 at the time of recording, and is read from the magnetic tape and read to the buffer memory 3 at the time of reproduction. It performs error correction for the stored read data. When a predetermined amount of data transferred from the host computer is recorded in the buffer memory 3, under the control of the system controller 4, the main data recorded in the buffer memory 3 is added with an error correction code. The data is output to a serial / parallel converter (S / P) 6 and further sent to a DAT data processor 8. In the system controller 4, subcode data is generated and sent to the DAT data processing unit 8 via the I / O unit 7. The DAT data processing unit 8 generates recording data in a predetermined format based on the main data to be recorded and the subcode data sent from the system controller 4. The data recording / reproducing unit 9 is driven and controlled by a mechanical controller 10, and the recording data generated by the data processing unit 8 is recorded on a magnetic tape.

FIG. 2 shows a recording state on a tape.
The recording data generated by the DAT data processing unit 8 is recorded on the magnetic tape T by a helical scan method by a magnetic head provided in the rotary head device 9a. In FIG. 2, recording is performed in the order of tracks T1, T2,..., But in each track, a format is used in which recording areas 21 for subcode data exist at the upper and lower ends of a recording area 20 for main code data. Then, one track is formed by two tracks. Data such as a track number and a frame number are recorded in the recording area of the subcode data.

Next, a method for calculating the recording capacity according to the present invention will be described. In the format area shown in FIG. 4, the total length of the tape T is N (mm), the length of the user recording area 35 where the user can record data is U (mm), and the start of the tape where the user cannot record is prohibited. The length of the area 30 is Q1 (mm), and the length of the prohibited area 34 at the end of the tape is Q2 (mm). Also, set the tape speed to S (mm /
s), the rotational speed of the cylinder in the rotary head device 9a is R
(Rpm). Further, the last frame number in the already recorded area 31 is Fp, and the amount of data recordable in one frame is Df (byte). The data amount Df that can be recorded in one frame corresponds to the recording area 2 of the main code data for two tracks in the format shown in FIG.
This is the recording amount of main data that can be recorded at 0. From the above, the length U of the user recording area 35 is obtained as shown in Expression 1.

[0015]

## EQU1 ## U = N- (Q1 + Q2)

Assuming that the total number of frames recordable in the user recording area 35 having the length U is Ft, this Ft can be expressed by Equation 2.

[0017]

Ft = {(U / S) / (60 / R)}

(U / S) is the total time (s) during which the user recording area 35 runs, and (60 / R) means the time (s) for one rotation of the cylinder. The rotary head device 9a provided in the data recording / reproducing unit 9 shown in FIG. 1 is of a two-head type in which a magnetic head H is mounted on a cylinder at an interval of 180 degrees.
, Data for two tracks, that is, data for one frame is recorded. Therefore, the total number of frames Ft recorded in the user recording area 35 is calculated by dividing the total time (s) during which the user recording area 35 travels by the time (s) during which the cylinder makes one revolution.

From the above equations (1) and (2), assuming that the number of frames that can be recorded in the unrecorded portion in the user recording area 35 of the magnetic tape is Fr, this Fr can be obtained by equation (3).

[0020]

## EQU3 ## Fr = Ft-Fp

Further, assuming that the data amount that can be recorded in one frame is Df (byte), the data amount Dr that can be written to the unrecorded portion of the user recording area 35 is as shown in Expression 4. .

[0022]

## EQU4 ## Dr = Fr × Df

The above calculation is mainly performed by the CPU in the system controller 4. That is, at the time of recording, the sub-code data including the frame number is generated by the system controller, and at the time of reproduction, the sub-code data of the data read from the magnetic tape T is recognized by the system controller 4. Therefore,
For example, when new data is recorded immediately after the last frame (Fp) in FIG. 4, an EOD is searched for by a search operation, and then the tape is rewound to complete the last frame (Fp).
The tape is advanced in the reproduction mode to the position of. The system controller 4 can read the frame number (Fp) of the last frame from the subcode data reproduced at this time. When the last frame number Fp is recognized, the remaining recordable frame number Fr and the recordable data amount Dr are calculated.

Hereinafter, steps for the above calculation will be described with reference to FIG. Step 1 (ST1): When a tape cassette is loaded, information on a tape type and a tape thickness is obtained from a type hole formed in the cassette. Thereafter, the magnetic tape is rotated at a constant speed, and the rotation speeds of the supply-side reel base and the take-up reel base at this time are calculated,
The tape length is determined from the ratio between the two rotation speeds. When the tape length is determined, the tape length U of the user recording area 35 shown in Expression 1 is immediately calculated.

Step 2 (ST2): Based on the above U, the calculation represented by the above equation 2 is performed, and the user recording area 35 is calculated.
Is calculated. Step 3 (ST3): In the user recording area 35, a search is made for the last frame (Fp) of the already recorded area. As described above, this search is performed by running the tape at a high speed, rotating the cylinder of the rotary head device 9a at a high speed, detecting the EOD, rewinding the tape slightly immediately after that, and then ending the playback mode. This is performed by reading up to the frame. The subcode data including the frame number is read into the system controller 4 via the DAT data processing unit 8, the frame number Fp of the last frame is recognized by the system controller 4, and the number of frames already recorded is determined. I understand.

Step 4 (ST4): The frame number Fp detected in step 3 is subtracted from the total number Ft of recordable frames calculated in step 2 to calculate the number Fr of frames recordable in an unrecorded area. You. Step 5 (ST5): From the above Fr, the recording area 20 of the main code data of each track in the unrecorded area
The total data amount Dr that can be recorded in the destination is calculated.

According to the above steps, the system controller 4 sets the user recording area when the magnetic head H of the rotary head device 9a can start writing immediately after the last frame (Fp) shown in FIG. 4, for example. 35
Can be recognized as the data amount Dr that can be recorded in the unrecorded portion of.
Therefore, various controls can be performed by knowing the data amount DR recordable in the unrecorded portion. This control is appropriately determined by an interface with the host computer. For example, by the SCSI bus Mode Sense command, the remaining tape capacity is transferred to the host computer by the data amount Dr.
On the display of the host computer,
The data may be displayed as the remaining capacity of the magnetic tape T, or the host computer may compare the remaining capacity of the magnetic tape with the amount of data to be transferred for backup and load the data on the data recording / reproducing unit 9. It may be determined whether or not all backup data can be stored on the magnetic tape, and an indication of whether or not the magnetic tape should be replaced may be displayed.

Alternatively, as shown in FIG. 1, a unique display device 11 linked to the system controller 4 is provided,
The remaining capacity that can be recorded on the magnetic tape may be displayed on the display device 11. Also, in a so-called partition method in which a magnetic tape is divided into a plurality of areas and, for example, different types of data are independently recorded in the respective divided areas, if the tape length up to a boundary position where the areas are divided is known. In the same manner as above, the remaining capacity of the user recording area in each area can be obtained.

For example, in the case of two partitions, empty data is usually sequentially recorded in the first divided area starting from the beginning of the tape, and formatting is performed. When the formatting is completed, the boundary of the divided area is reached. The frame number of the portion, that is, the frame number of the last frame of the first divided area is known. This frame number is the total number of frames that can be recorded in the first divided area. The length of the user recording area of the magnetic tape and the total number of frames Ft that can be recorded in this user recording area can be calculated from the above equations 1 and 2, and the final frame number of the first divided area can be calculated from the total number of frames Ft. By subtracting the frame number, the number of frames that can be recorded in the second divided area can be calculated. As described above, by calculating the number of frames that can be recorded in each of the divided areas, when data is subsequently recorded in each of the divided areas, a frame that can be recorded in the unrecorded area is recorded for each of the divided areas. The number and even the amount of data can be calculated.

Although the above embodiment has been described in connection with the case where a DAT for data backup is used, the present invention is applicable to any rotary head type digital equipment, for example, digital video. Furthermore, the present invention can be implemented in digital recording of a fixed head system.

[0031]

As described above, according to the present invention, the amount of data recordable in the unrecorded area of the magnetic tape can be recognized as the number of frames and the data amount. It will be possible to reliably recognize whether it fits in the area.

Even when the recording area of the magnetic tape is divided into a plurality of areas, the recording capacity of the unrecorded portion can be reliably grasped as the data amount for each of the divided areas.

[Brief description of the drawings]

FIG. 1 is a block diagram of a rotary head digital audio tape recorder (DAT) for performing the method of the present invention.

FIG. 2 is a conceptual diagram showing a recording state of a tape.

FIG. 3 is a flowchart illustrating an operation according to the method of the present invention.

FIG. 4 is an explanatory diagram illustrating a recording format over the entire length of a tape T.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 SCSI bus 2 SCSI controller 3 Buffer memory 4 System controller 5 ECC circuit 6 Serial / parallel conversion part 7 I / O part 8 DAT data processing part 9 Data recording / reproduction part 10 Mechanical controller 11 Display device

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G11B 27/00 G11B 15/02 G11B 20/12

Claims (1)

(57) [Claims] (1) two tracks of data to be recorded on a magnetic tape;
The magnetic tape slides diagonally with the magnetic tape as one frame.
During one rotation of the air head, the data for one frame
Is written on the magnetic tape, wherein each of the plurality of divided recording areas of the loaded magnetic tape is
Calculate the number of frames that can be recorded on the
Subcode data issued, for each recording area, detecting the last frame number of the data already recorded
The final frame is calculated from the number of frames in each recording area.
A recording capacity calculation method for a magnetic tape device, wherein a recording capacity is calculated for each divided recording area by subtracting a number .