JPS6361490A - File positioning system - Google Patents

Abstract

PURPOSE:To realize a high speed read/write operation after positioning by calculating the quantity of the shortest movement between a designated tape mark position and a head position after tape mark detection command is received and positioning the head. CONSTITUTION:A physical track number, a tape mark sequence number, a byte position and a control flag written in the tape mark control clock of a magnetic tape are read by the head 1, data is processed in a disqueuing buffer 4, detected in a TM control detection circuit 12 and stored in a memory 7. Then, the command received in a command decoder 13 from an MTC control part 10 is decoded, the memory 7 is read by the output of a counter 14, from an object TM position and the head position, the quantity of the movement and a direction are calculated in a movement quantity offset calculation circuit 18, and a tape driving system 20 is controlled by a tape movement control circuit 19 to position the head 1 at an object position.

Description

[Detailed Description of the Invention] [Summary] The present invention is a serpentine magnetic tape device that performs read/write processing on two tracks in parallel. Even if it receives a tape mark detection command based on the above, it does not immediately perform mechanical operation, but calculates the shortest movement lid and direction between the specified tape mark position and the current head position,
Position the head at a predetermined position when a read/write command is generated. This allows the magnetic tape file to be located at high speeds, and therefore read/written at high speeds.

[Industrial application field]

The present invention relates to a file positioning system that achieves high-speed read/write of the head of a serpentine magnetic tape device.

[Traditional technique + i? , 1 Conventionally, the file positioning method in a magnetic tape device is as follows: In the normal magnetic tape system shown in FIG. From to each 7 isle condyle (1) t (2) e...
etc. 9, magnetic tape controller (MTC)
) When a space file command is given, the head is positioned at a predetermined file by counting the tape marks in the space direction forward or backward from the current position, and reading/writing is performed.

With this method, for example, there is no convenient way to position the tape from the current position to TM (4) other than to advance the tape forward.On the other hand, recently, with the aim of increasing file capacity and downsizing, the serpentine method, which is stored in a cassette, has been developed. Magnetic tape devices have been proposed and are being put into practical use. FIG. 2B is a schematic explanatory diagram of a serpentine magnetic tape. That is, a 1/2 inch wide tape is divided into 20 tracks, and read/write processing is performed on two tracks in parallel. Between both LPs, even-numbered tracks are processed from EOT to BOT, odd-numbered tracks from tBOT to EOT, and tracks 0 and 1 are processed on the EOT side, tracks 1 and 2
The number track is connected to the EOT side. If we consider two physical tracks as one logical track, it becomes a logical qio track, which means that there are five
Read/write is performed back and forth.

For example, files (A) and (B) as shown in the figure.

(C), (D), etc. are stored in a ring shape, and when the control section of the magnetic tape controller 7 (MTC) specifies the position of the D file relative to the current position,
Give the space direction/ille commands kA, B+C, and D in sequence to reach the designated position. That is, after moving back and forth along the physical track A-B-C-D, the file D is reached and read/written. In this way, in the serpentine system, as in the conventional system, when a space file command is received, LP and TMk are detected, and the corresponding file is moved and located.

(C) is a schematic explanatory diagram of a serpentine type TM control detection section. In the same figure, track information detected by a head 1 belonging to a magnetic tape unit (MTU) is transferred to a peak detection circuit 2.
The peak point is detected and demodulated by the demodulation circuit 6.

This output is sent to a magnetic tape controller (MTC) for synchronization stabilization) and input to a deskewing buffer 4, where a window is provided to detect an information pattern. This pattern is passed through the LP determination circuit 5 to determine the LP position, and
If it is a TM pattern after P has passed, this is temporarily stored in the distal register. This content is also included in the MTC control unit 10! By control, the same content in the υ memory (MEM) 7 is compared and judged, and read/write operation or movement to the next file is performed. [Problems to be solved by the invention] The above serpentine method The read/write positioning system moves the tape according to the four tracks shown in FIG. 4(b) in response to each space file command, as will be described later in the diagram explaining the principle of the present invention in FIG. When you do this, the specified file position will move away from the current position, move closer to it, and further move away in the opposite direction across the current line. That is, it takes an excessive amount of time to move from the current position to the file commands in order and repeat the movement each time.

Therefore, even if a file command is received, the tape should not be moved immediately, but the tape should be moved directly from the current position in the shortest possible time after waiting for the TM designation of the final file.

An object of the present invention is to provide a file positioning method that allows a serpentine magnetic tape device to move from the current position to a specified file position 11 in the shortest possible time. In order to achieve the above object, in the present invention, tape mark information written on a magnetic tape is read, and even if a tape mark detection command based on the information is received, no mechanical operation is performed immediately, and the specified The shortest amount of movement and direction between the current head position and the current head position are calculated, and the head is positioned at a predetermined position when a read/write command is issued.

[For production]

With the above configuration, as shown in the principle diagram of FIG. 1, the amount of tape movement from the current position can be adjusted by the conventional method shown in FIG. 4 (α), the serpentine method shown in FIG. ■ for each case.

The comparison is shown using @ and θ.

In other words, the conventional method of ■ is to move file (3) from the current position.
I (4) and increases, whereas in @'s serpentine method, file (A) increases in the positive direction,
It decreases in file (B) and further in the opposite direction (C
) and increases again in the positive direction until it reaches the specified file ■). During this time, the tape was transferred wb'! jt becomes very large.

In the method of the present invention shown by the bold line θ, the amount of movement and time can be significantly reduced because it is only necessary to switch the tape from track A to track D and go directly to reach the designated file CD from the current position.

〔Example〕

FIGS. 2(α) and 2(b) are explanatory diagrams of a TM control detection unit which is a main part of an embodiment of the present invention.

The difference in FIG. 4(α) from FIG. 4(G) is that a branched TM control detection circuit 12 is provided between the die skewing buffer 4 and the LP detection circuit 5. Furthermore, as shown in FIG. 2(b), a TM control block 11
will be established. The block is composed of (1) physical track number, (2) tape mark order number, (2) byte position, (2) control flag, etc., and is written in advance. When the serpentine cassette is first mounted, the contents of this TM control block are read by the head 1 shown in the figure (α), and the data is processed from the peak detection circuit 2 to the deskewing buffer 4 in the same way as for TM. After performing TM, which is the main part of the present invention,
At the control detection time w112, the control #j information is detected,
It is stored in the memory (MEM) 7 via the LP determination circuit 5.

The contents of the memo u (MEM) 7 are stored in the memory (MEM) 7 by rewriting and reading the TM control block for modification after mounting the tape cassette during non-operation using a conventional head mechanism. Update.

FIG. 3 is an explanatory diagram of a control circuit, which is positioned as a main part of the present invention.

The control circuit is an MTC controller controlled by the MTC controller 10.
The tape drive control is performed with respect to the head position of the CMTU by a space file command based on the TM control block stored in the memo') (MEM) 7 shown in FIG. 2 (α).

In the figure, the MTC control unit 10 decodes the command received by the command decoder 16 and creates a forward space file CF.
SF), backward space file (BSF).

or other commands (read/write R/W here)
Determine whether The FSF signal and BSF signal are processed by the counter 14.
9, the FSIM signal is calculated by force, and the BSF signal is subtracted.

That is, the counter 14 holds the number of tape mark (TM) t to be moved from the current position. The count output of this counter 14 causes memory (MEM) 7'
, and determine which track and byte position the target file is located based on the TM order number contained therein.
The target TM position from the memory (MEM) 7 is held in the TM position register 16, while the current position of the head is held in the current position register 17. The outputs of both of these are input to the movement amount offset calculation circuit 18, and the movement amount and movement direction from the current position to the target position are calculated and determined.

Further, the FSF signal or BSF signal from the counter 14 and the R/2 bit (R/v) signal from the command decoder 13
) signal is input to the drive condition determination circuit 15, and the 0FSF signal or BSF signal immediately before the read/2 write signal is determined. When a space file signal under this condition is generated, the movement amount and movement direction from the movement amount offset calculation circuit 18 are sent to the tape movement control circuit 19, and the drive direction, that is, forward or reverse, is sent to the tape movement control circuit 19. The drive is controlled by a predetermined amount of movement in the direction and the direction perpendicular to the direction. In this way, the head can be positioned at the target position.

〔Effect of the invention〕

As explained above, according to the present invention, the server tie 7
For the magnetic tape data format of this method, instead of using the space command to move to the target position as in the conventional method, it is possible to position from the current position to the previous target position with the minimum O transfer weight. Therefore, the positioning is such that subsequent read/write operations can be accomplished in the shortest possible time.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the main part of the present invention, and FIG. 2 (α). (6) is an explanatory diagram of the TM control detection section of the main part of the embodiment, FIG. 6 is an explanatory diagram of the control circuit, and FIG. 4 (α
) to (c) are explanatory diagrams of conventional examples, in which 1 is a head, 2 is a peak detection circuit, 3 is a demodulation circuit, 4 is a deskewing buffer, 5 is an LP judgment circuit, 6 is a register,
7 is memory (MEM), 10 is MTC control unit, 11 is T
M control block, 12 is a TM control detection circuit, 16 is a command decoder, 14 is a counter, 15 is a drive condition determining circuit, 16 is a TM position register, 17 is a current position register, 18 is a shift 'Itb amount offset calculation circuit, 19 2 shows a tape movement control circuit, and 20 shows a tape drive system (MT U ).

Claims (1)

[Scope of Claims] A serpentine magnetic tape device that performs read/write processing on two tracks in parallel, including at least a physical track number, a tape mark order number, and a byte position written near the starting end of the magnetic tape. means for reading tape mark control information; and means for receiving a tape mark detection command based on the tape mark control information and calculating the shortest movement amount and direction between the tape mark position specified by the command and the current head position. and a tape drive means for positioning the head based on the calculation result when a read/write command is generated.