JPS6128181B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a block detection method for accessing a desired block at high speed in a recording apparatus using magnetic tape as a recording medium.

One of the methods commonly used at present for high-speed access to data blocks written on a magnetic tape is to detect a clock in the preamble and read and detect data at the timing of this clock. However, in such a system, a circuit for detecting a clock and reading data in synchronization with the clock becomes complicated.
Furthermore, when controlling with a CPU or the like, it is necessary to always judge whether the read data is what is needed.

Furthermore, since access becomes impossible if there is a sudden change in the speed of the tape, it is possible to prevent an equally sudden change in speed that would require applying back tension or the like to the tape. Therefore, it is necessary to increase the torque of the tape drive motor. In view of the above, the above method cannot be said to be a very effective means when it is sufficient to detect a desired block from a group of blocks in which each piece of data is classified.

Therefore, the present invention aims to provide a simple means for detecting a desired block among a large number of blocks. That is, a block for position detection is provided at the head (starting end) of each block. This position detection block length is set longer or shorter than each data length in the block. A desired block is detected by detecting the block length and counting the position detection blocks.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows a format for writing data etc. on a magnetic tape, and FIG. 2 is an enlarged view of the main part of FIG. In the figure, BOT is a mark (for example, a hole) for detecting the starting end of magnetic tape 1.
Further, EOT is a mark for detecting the end of the magnetic tape 1. In other words, the above mark BOT,
By detecting EOT, the beginning or end of the tape is detected. Moreover, as shown in FIG. 2, the code 2...
Data block D where a large amount of data is written.
This block has a control block CB in which information for position detection is recorded before the first data block DB1.
Each block 2 is a collection of a large number of data, such as data of the same item or classification.
In addition, the data block DB and position detection block
The I provided between the CB and the CB is an interblock gap indicating a division (separation) between each data block, etc., and no information is recorded therein.

Therefore, in the present invention, the length Ld of the data block DB in which each data is written, and the control block C in which information for position detection is recorded.
The length Lc of B is set so as to satisfy the following conditions.

Lc/Vmin<Ld/Lmax (When set as Lc<Ld) Lc/Vmax>Ld/Vmin (When set as Lc>Ld) However, Vmin: Minimum tape speed when fast forwarding and rewinding the tape Vmax: Maximum Tape Speed During Fast Forwarding and Rewinding of the Tape An embodiment of the present invention will be described in the case where Lc<Ld.

Running the magnetic tape recorded as above,
A control circuit for detecting a desired block among the blocks 2 is shown in the block diagram of FIG. In this block diagram, 3 is a deck for reading information written on tape 1 (data written to DB or CB, etc.) or writing information. The deck is controlled by a control circuit 4. Input data is input to this control circuit, and the deck 3 is controlled according to this input data. For example, if the input data specifies the n-th block 2n, the control circuit 4 stores the numerical value n and issues a fast forward command to the tape drive motor of the deck 3. However, in this case, tape 1 is assumed to be at the tip. Therefore,
Tape 1 is fast forwarded and each CB,
Information written to the DB is read. This read signal is then input to the pulse width conversion circuit 5, and a signal as shown in FIG. 4a is obtained. That is, the pulse width conversion circuit 5 outputs a signal with a pulse width corresponding to the lengths Lc and Ld of the control block CB and data block DB as shown in FIG. The pulse td in FIG. 4a is a signal corresponding to the block length of the data block DB, and the pulse tc
is a signal corresponding to the block length of control block CB.

Next, the signal from the pulse width conversion circuit 5 is input to the next stage pulse width discrimination circuit 6. This pulse width discrimination circuit 6 detects the difference between the pulse td and the pulse tc, and outputs, for example, a logical value "1" when a pulse tc of a determined width (see FIG. 4b) is input. That is, the pulse width discrimination circuit 6 stores the length of either the reference pulse td or the pulse tc, and compares it with the length of the signal input from the pulse width conversion circuit 5 to determine whether the control block CB
The pulse tc corresponding to the block length of is detected. The output signal is input to the control circuit 4.
Therefore, the signals shown in FIG. 4b are counted by the control circuit 4, and when this count reaches n,
A stop signal is output from the control circuit 4 to the deck 3, the running of the tape 1 is stopped, and the desired n-th block 2n is detected. In this case, the n-th control block CB and the n-th control block CB
The first data block in the block D.
Since there is an interblock gap I between tape I and tape B, the stop position of tape I according to the stop signal will be within the range of interblock gap I. In other words, the interval between the interblock gaps I is determined by the distance the tape travels from when the pulse width discrimination circuit 6 starts detection until the control circuit 4 outputs a stop signal to the deck 3 and the tape 1 stops. The interval is set to be sufficiently larger than that of .

The desired block is detected as described above, and even when detecting a desired block from the middle of the magnetic tape 1, if the previous block position is memorized, the input block position can be easily detected. The magnetic tape can be stopped at a desired block position by calculating the difference between the two and fast forwarding or rewinding the tape 1 according to the difference.

As explained above, in the present invention, a block consisting of a large number of data blocks D.B1 to D.Bn separated by interblock gaps is
Further, in a recording device using a magnetic tape as a recording medium, in which blocks are sequentially recorded as block groups 2, 2, etc. separated by an interblock gap, position detection is performed at the leading position of each block of the block groups 2, 2, and so on. The data block at the beginning of the control block CB in which the data for
D.B1 is provided with an intergap between the block and the control block length CB, and the control block length CB is set in the relationship of DB<CB or DB>CB with respect to each data block length DB in the block group. A pulse width conversion circuit outputs signals corresponding to the data block lengths DB and CB based on a tape read signal, and a signal from the circuit is input, and a control block CB is detected based on the difference in the input signal lengths. , a discriminating circuit that outputs a detection signal is provided, and each block is detected by counting the detection signal from the discriminating circuit, so unlike the conventional method, data in each block is unnecessary or unnecessary. To provide a simple configuration in which a desired block can be quickly detected and feeding of the tape can be stopped at that position by simply providing a control block at the head of each block without the need for such detection.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the format in which data is recorded on the tape, and FIG. 2 is an enlarged view of the main part shown in FIG. 1, showing the recording format in one block,
FIG. 3 is a block diagram showing a control circuit according to the present invention, and FIGS. 4a and 4b are output waveform diagrams of each circuit in FIG. 1: Magnetic tape, 2: Block, CB: Control block, DB: Data block,
5: Pulse width conversion circuit, 6: Pulse width discrimination circuit.

Claims (1)

[Scope of Claims] 1. A large number of data blocks D.B1 to D.Bn separated by interblock gaps are divided into block groups 2, 2, etc., which are further distinguished by interblock gaps. In a recording device using a magnetic tape as a recording medium, the control block CB, in which position detection data is recorded, is placed at the head position of each block of the block groups 2, 2, etc., and the control block CB, in which position detection data is recorded, is placed in the head data block D. .B1, and the control block length CB is set in the relationship of DB<CB or DB<CB with respect to each data block length DB in the block group, and on the other hand, the magnetic tape A pulse width conversion circuit outputs a signal corresponding to the data block lengths DB and CB based on a read signal of the circuit, and a signal from the circuit is input, and a control block CB is detected based on the difference in the input signal length. 1. A block detection method for a magnetic tape, characterized in that a discrimination circuit for outputting a signal is provided, and each block is detected by counting detection signals from the discrimination circuit.