JPS6249434A - Cartridge magnetic tape device - Google Patents

Abstract

PURPOSE:To shorten data transfer time by writing dummy data by the number of blocks, which has been set in advance, in case of it has been detected that the data to be written does not exist in a buffer means. CONSTITUTION:When the data are transferred to a buffer circuit 20 from a recording/reproducing circuit 23 and stored by a block unit, in case of a regular data block, the contents of N102 of a buffer circuit 22 are inputted to a data number detecting circuit 29. Subsequently, the value of N102 and the contents of a block size counter 25, namely, a count value of a strobe signal 5 are compared by a comparing circuit 30, and when they have coincided, the block is updated to the next block. In case of a dummy block, the contents of N102 are '0', therefore, when an input from the data number detecting circuit 29 is received, the comparing circuit 30 outputs a signal 11 immediately, and updates the block to the next block. In this way, the titled device is constituted so that the dummy data block is recorded in a tape at the time of a buffer under-line, therefore, the decrease of a data transfer speed is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cartridge magnetic tape device having a streaming function.

(Prior Art) In recent years, large-capacity storage devices have been required even in small devices such as personal computers. In response to this demand, burner computers equipped with hard disks (with a recording capacity of 20 Mbytes, for example) using Winchester technology have also appeared.

However, although this hard disk has the advantage of large capacity and high speed, it also has the disadvantage that the recording medium is fixed and cannot be replaced. To compensate for this shortcoming, a device for backing up the recorded contents of a hard disk is used as part of a personal computer.

The above-mentioned backup device is a cartridge magnetic tape device (hereinafter abbreviated as CMT device) that has a large capacity (e.g. 20 MB), high speed, and low price and has a streaming function that performs continuous data transfer with a single startup. ) is used.

FIG. 2 is a diagram showing an example of the format of a cartridge magnetic tape.

5YNC100 is a bit string for synchronizing the recording and reproducing circuit when recording and reproducing data on a magnetic tape. A
DDRESSlol indicates the address of the block. N1
02 indicates the number of valid data recorded in DATA103. DATA103 is a data recording area.

In the following description, it is assumed that DATA 103 has a fixed length of 512 bytes. For example, when recording 500 bytes of data, 12 bytes of invalid data (also called dummy data).

) is added, and DATA 103 is always recorded with a fixed length of 512 bytes. At this time, N 102 holds 500, which is the number of valid data. CRC 104 is an area for recording the result of CRC check.

FIG. 2 is a block diagram showing an example of the configuration of a conventional CMT device. A buffer circuit 20 is composed of a plurality of blocks and is stored in the DATA 103 in units of bytes. In addition,
In the following explanation, one buffer block and file block = 512 bytes.

The explanation will be made assuming that the number of blocks is 4 blocks. 21 is a buffer circuit for storing the address to be recorded in ADDRESSlol in the format described in FIG. 2, and is composed of four blocks. Similarly, 22 is a buffer circuit for storing the number of valid data to be recorded in N 102 in FIG. 2, and is composed of four blocks. A recording device that records and plays back serial data on magnetic tape (hereinafter abbreviated as tape).
This is a regeneration circuit.

24 is a host central processing unit (
(hereinafter abbreviated as host device). 5 is a block size counter, which counts at the timing of the read/write strobe signal, and normally has a buffer block size of 51.
Cleared with 2. When the count reaches 512, valid data register 26E512 is set. Further, the flock size counter 5 is also cleared when the stop signal 4 is input. 26 is a valid data register in which the count value of the block size counter until the stop signal 4 is input is set. 27 is a block count register, which is incremented each time the block size counter 5 is cleared as described above, and becomes data to be recorded in ADDRESSlol shown in FIG.

Therefore, a block designation signal 13 indicating which block of each block of the buffer circuit to store data at the time of writing is output by decoding the lower two bits of this register. The circuit is a dummy data set circuit that writes valid data into the buffer when the valid data in the block is not 512 bytes, and also generates a write strobe from itself and synchronizes writing to the buffer circuit 20. Reference numeral 29 denotes a data number detection circuit that reads the number of valid data from the valid data number storage/storage area 22 when reading data. A comparison circuit 30 compares the number of valid data read by the data number detection circuit 29 and the number of data transferred to the host device U.

Next, signals and signal lines will be explained.

1 is a data bus connecting the buffer circuit 20 and the host device 24. 2 is a serial data line connecting the buffer circuit 20 and the recording/reproducing circuit. Reference numeral 3 denotes a dummy data write line for writing dummy data (invalid data) into the buffer circuit 20. 4 is a read/write stop signal (hereinafter abbreviated as stop signal) indicating the end of data read and data write. This stop signal 4 activates the dummy data set circuit and clears the block size counter 25. 5 is a read/write strobe signal (hereinafter abbreviated as strobe signal). 6
is a read/write signal indicating whether the CMT device is in a read operation or in a write operation. 7 is an effective data number write line for writing the contents of the effective data register 26 into the buffer circuit n. 8 is a comparison circuit (9
). 9 is a data number input line from which the value of N102 in the block is read at the time of reading.

1o is a valid data number input line for inputting the detected valid data number to 26 comparison circuits. 11 is 1 when leading
This is a next block transfer request signal indicating that all valid data in one block has been transferred to post n and requesting transfer of the next block data. 12 is ADDRESSl
This is a block address line for inputting the block address to be recorded in the buffer circuit 21 to the buffer circuit 21. 13 indicates the address of which block the signal on the block address line 12 corresponds to. is the input signal.

Next, the operation of the conventional CMT device will be explained. First, a data write operation for writing data onto a tape will be explained. The host 24 transfers 1 byte data to the buffer circuit 20 via the data bus 1 by turning on the strobe signal 5. Therefore, n-byte block data is transferred to the buffer circuit side by turning on the strobe signal 5 n times, and the number of transferred data is determined by the number of times the strobe signal 5 is turned on using the block size counter 5. It is obtained from counting K. When this count reaches the block size 512 of the data buffer, the serial data with this as one block is transferred to the buffer circuit 20.
The data is then recorded on a tape via the recording/reproducing circuit 21.

Also, the number of valid data stored in the corresponding block of the buffer memory 21 from the valid data register 26 is recorded on the tape as N102, and the block address stored in the corresponding block of the buffer memory 21 from the central block count register n is recorded on the tape as ADDRESSlol. recorded.

The data after the 513th byte is also the same as the data from 1st to 512th bytes. In other words, when the 512th byte strobe signal 5 is input to the block size counter 5,
“512” is output to the valid data register 26. At this time, counter 5 is cleared.

At the same time, block count register n is incremented. Now, if 512 bytes of data of the n-th block is transferred to the buffer circuit 21, the buffer circuit 21
, 22 are set to ADDRESS=nN2512, respectively. The tape has n, 512 and 1
~512 bytes of data are recorded as the nth block. Even if the data of the 10th and 1st block, that is, the 513th byte, and the strobe signal 5 are transferred while the n-th block is being recorded on the tape by the recording/reproducing circuit through the serial data line 2, the data will be transferred in the same way as the n-th block. Buffer circuit 20
, 21 and 22, data, data, block address, and number of valid data are stored, respectively. As described above, data is stored in all four blocks of the buffer circuit silver, which is the buffer full state, and the host device 2
The data transfer from the host device U is temporarily interrupted, but the data is recorded on the tape K. When one of the Shibara hard blocks becomes empty, the data transfer from the host device U is resumed.

If the data to be written is less than the buffer block size of 512 bytes, the block size is changed by inputting the stop signal 4 from the host device 24.

The counter 5 sets the value counted up to that point in the valid data register 26, and also increments the block count register n by one. Further, upon input of the stop signal 4, the dummy data set circuit 28 stores dummy data (for example, FF) in the buffer circuit silver by the number of times (512-valid register contents). When buffer circuit silver reaches buffer block size 512, buffer circuit 21
, 22, and 20 can be transferred to Party B. FIG. 4 is an example in which the buffer size of the first block is less than 512. When the stop signal 4 is input after the 510th byte strobe signal 5 is input, the valid data number N is input to the buffer circuit 22 while the stop signal 4 is on, and the last dummy data is stored in the buffer circuit 20. After that, ADDRESS is stored in the buffer circuit 21. Here, the data can be transferred from the buffer circuits 20, 21, and Z3 to the recording/reproducing circuit n.

FIGS. 5(a) and 5(b) show specific examples of recording on tape.

FIG. 5(a) is a schematic example, and FIG. 5(b) is a schematic example.
This is a detailed example of the (n+1)th block in a).

The nth block shown in FIG. 5(a) is an example in which all data corresponding to the buffer block size of 512 bytes is recorded. 512 is recorded in N102, and the valid data is 512.
It's a part-time job. In the (n+1)th block, valid data is 10 bytes. 10 is recorded in N102.

As shown in FIG. 5(b), the DAT of the n+1 block
Increment data from OOH to 09H is recorded in the A103 portion. Numeric value O in 1 to 10 bytes
It can be seen that 09H is recorded from OH, and FF data is recorded from the 11th byte to the 512th byte.

Next, a data read operation for reading data from the tape will be explained.

When the host device 24 sets the read/write signal 6 to a read state, the serial data read from the tape by the recording/reproducing circuit 23 is stored in the buffer circuit 20, and is read into the buffer circuit 20 at the end of reading one block of data. The number of data detected, that is, the contents of N102, is transferred to the data number detection circuit 29.

Here, when the strobe signal 5 is input to the block size counter 5 and the buffer circuit m, this strobe signal 5
From the buffer circuit 20 to the host device 2 at 0 input timing
1 byte of data is transferred to 4. By counting the strobe signal 5 in the block size counter section, the count value and the number of valid data read out by the data number detection circuit 29 are compared in a comparator circuit (9). When all the number of valid data has been transferred to the host device 24, the block size counter '25 has counted up to a value equal to the number of valid data, so the output signal 11 of the comparator circuit 30 is turned on and is input to the buffer circuit 20 and the next Request a block transfer. At this time, the next block is the buffer circuit 20.
, 21, and 22, the strobe signal 5 is input from the host 24, and the block size counter starts counting the transferred data again.

For example, the contents of N102 read from the tape and transferred to the data detection circuit 29 have a buffer block size of 51.
If it is 2 bytes, the corresponding block of the buffer circuit 20 stores 512 bytes of valid data. When data transfer to the host device 24 is started at the timing of the strobe signal 5, the block size counter 5 counts the strobe signal 5. Value counted by block size counter 5 and contents of data detection circuit 4 512
are compared using a comparator circuit. If there is a match, the comparison circuit 30 inputs the next block transfer request signal 11 to the buffer circuit and transfers the next block starting 1. In other words, a request is made to transfer the 513th byte of data. Thereafter, the same operation is performed by inputting the strobe signal 50.

If the valid data in the block is still less than the buffer block size of 512 bytes, add the buffer.

After being read from the tape and stored at 21.22, when the value of N102 transferred to the data number detection circuit 4 and the value of the block size counter 5 match, the next block transfer signal 11 is transferred to the buffer circuit side. , and dummy data is ignored. For example, when valid data is 510 bytes, 2 bytes of invalid data are stored in the buffer circuit 20 but are not transferred to the host device 24.

(Problems to be Solved by the Invention) However, in the CMT device having the above configuration, the buffer circuit 2
If a buffer underrun occurs in which the buffer circuit becomes empty and there is no data to be written due to a lack of 0 capacity or a long software processing time on the host device, etc., this buffer underrun will occur. There is a problem in that the data transfer speed is significantly reduced due to the rotation caused by this. Incidentally, what is meant by "revolutioning" here is that when there is no data to be written to the tape in the data buffer, the CMT device cannot stop running immediately, so as shown in Figure 6, the CMT device runs to the next block or beyond, and then,
This refers to the operation of rewinding in area 1 that has already been written, running again to the next block written last, and then stopping the tape drive.

It is an object of the present invention to provide a cartridge magnetic tape device that can reduce time.

(Means for Solving the Problems) In order to solve the above-mentioned problems of the present invention, a streaming type cartridge is provided with a buffer means and transmits data in blocks to and from a central processing unit via the buffer means. The magnetic tape device includes a detection means for detecting an empty state of the buffer means, and a dummy data recording means for recording a preset number of blocks of dummy data on the cartridge magnetic tape based on an output signal of the detection means. It is something that

(Function) According to the present invention, since the cartridge magnetic tape device (CMT device) is configured as described above, the technical means functions as follows. During recording, the detection means detects an empty state in which there is no data to be written in the buffer means, and outputs a signal indicating the empty state to the recording means. The dummy data recording means operates to record dummy data for a predetermined number of blocks onto the cartridge magnetic tape following the recorded data. If the write data from the central processing unit is stored in the buffer means at the time when the recording of the dummy data is finished, it is possible to write this data to the magnetic tape following the dummy data without performing streaming. Become. Further, during reproduction, it is possible to ignore the number of blocks of written dummy data and read only valid data. Therefore, the problems of the prior art described above can be solved.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a CMT device of the present invention. In this figure, the same reference numerals as in FIG. 3 indicate the same components.

Reference numeral 31 is a flag register that sets 1 when data exists in each block of the buffer circuit silver, and sets 0 when no data exists. 32 is an OR gate that takes the logical sum of the flags in the flag register 31, and when all the flags are O, the output signal 16 is turned on.

33 is a dummy data block write circuit which is activated when the output signal 16 of the OR gate 32 is on and the read/write signal 6 indicates write, and writes the dummy data block to the tape from the serial data line 17. 34 is a dummy data block number setting circuit that sets the number of dummy data blocks to be written from the dummy data block write circuit 33 as an initial value by a program or the din 18w or the like.

A signal line 14 clears the flag register 3I (flag 0) when there is no data in each block of the buffer circuit. 16 is a signal whose output is turned on when all inputs of the OR gate 32 are O.

Reference numeral 17 denotes a dummy data write line outputted from the dummy data block write circuit 33. Reference numeral 18 is a data line for setting the number of blocks of dummy data to be written in the dummy data block write circuit 33, which is output from the dummy data block setting number scale.

Next, the operation will be explained.

First, a data write operation for writing data onto a tape will be explained.

Dummy data block setting circuit Sets the number of data to be written in case of buffer underrun.

For example, set it to 10 blocks. The subsequent data transfer is performed in exactly the same manner as described in FIG. 3, with the block size counter 5 counting the strobe signal 5 and storing data in the buffer circuit every 512 bytes of block size. Further, the buffer circuits 21 and 22 respectively store a block address and the number of valid data. When one block of data matches the block size, the serial data line 2 outputs the data and records it on the recording/reproducing circuit tape in the format shown in FIG.

As described above, data is recorded on the tape via the buffer circuit m. Also, normally, the data transfer between the host device 24 and the buffer circuit 20 is faster than the data transfer between the buffer circuit 20 and the recording/reproducing circuit 23;
is always buffer full. However, if the software processing on the host device 24 side is slow (in actual operation, write data is transferred from the hard disk to the main memory of the host device 24, it takes time to read from the disk and the software processing), Even if all the data is output to the recording/reproducing circuit and recorded on the tape (the next data is not sent from the host device U to the buffer circuit 20, the buffer circuit becomes empty. In CMT devices, if a gap equivalent to several blocks is written on the tape (a state in which no data blocks, etc. are written on the tape) and the next data is not transmitted during that time, repositioning is performed. Ta.

In contrast, in the embodiment of the present invention, the buffer empty state is detected by the flag register 31 and the OR gate 32, and the signal 16 is output. And when the read/write signal 6 indicates that a write operation is in progress, the dummy data block write circuit 33 is turned on, and outputs the dummy data block previously set in the dummy data block write circuit 33 to the data line 17 as serial data. , write to tape.

For example, the data of the dummy data block set in the dummy data write circuit 33 is a data block written in the ROM in advance. The dummy data block write circuit 33 writes dummy data blocks on the tape by the number of blocks set in the dummy data block number setting circuit 34 as a default value. If the next data is not sent to the buffer even after writing the specified number of dummy data blocks, repositioning is performed in the same way as in the conventional CMT device. However, if the next data is sent to the buffer circuit before all the specified number of dummy data blocks are written, the dummy data block write circuit 33 outputs all the data blocks currently being output and turns off. Transfer data line 2 to buffer circuit Silver. In the buffer circuit 20, when one block of transmitted data is complete, it is output to the recording/reproducing circuit path.

As described above, in this embodiment, when the buffer circuit Silver becomes buffer empty, a dummy data block is output from the dummy data block write circuit 33, and when data is sent to the buffer circuit Silver again, from the buffer 20. It is characterized by repeating the operation of outputting data blocks.

Next, a data read operation for reading data from the tape will be explained.

The data read operation when no dummy data block is written on the tape is the same as the case shown in Figure 3, so as explained in the data write operation, a buffer underrun occurs during writing and a dummy data block is written. We will explain only the case where

When data is transferred from the recording/reproducing circuit to the buffer circuit silver and stored in blocks, in the case of a normal data block, the contents of N102 of the buffer circuit n are input to the data number detection circuit 29, and the data is transferred between the comparison circuits. The value of N102 is compared with the contents of the block size counter, that is, the count value of strobe signal 5, and when they match, the block is updated to the next block. In the case of a dummy data block, the content of N102 is 0, so the comparison circuit 3
0 outputs the signal 11 immediately upon receiving the input from the data number detection circuit 29 to update the block to the next block. In other words, the contents of the dummy data block are not transferred to the host device 24.

As described above, in this embodiment, a dummy data block is recorded on the tape at the time of a buffer underrun, so a decrease in data transfer speed due to repositioning caused by a buffer underrun can be prevented, and a reduction in data transfer time can be expected. .

(Effects of the Invention) As explained above, according to the present invention, when it is detected that there is no data to be written in the buffer means, dummy data is written in a preset number of blocks, so that the data transfer time is reduced. can be shortened.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a cartridge magnetic tape (CMT) device of the present invention, FIG. 2 is a diagram showing an example of the format of a cartridge magnetic tape, and FIG. 3 is a block diagram showing a conventional CMT device. Figure 4 is a time chart showing the data write operation in Figure 3, Figures 5 (a) and (b)
6 is a diagram showing an example of actual writing on the cartridge magnetic tape, and FIG. 6 is an explanatory diagram of the beam positioning operation. Add...Buffer circuit, 24...Post central processing unit (host device), 5...Block size register, 26...Valid data register, n...Block count register, Ah... Dummy data set circuit, 2
9... Data number detection circuit, (capital)... Comparison circuit, 3
1... Flag register, 32... OR gate, 33
... Dummy data block write circuit, 34... Dummy data block number setting circuit.

Claims (1)

[Scope of Claims] A streaming type cartridge magnetic tape device that includes buffer means and performs data transfer in blocks with a central processing unit via the buffer means, further comprising a detection means for detecting an empty state of the buffer means. and dummy data recording means for recording a preset number of blocks of dummy data on the cartridge magnetic tape based on the output signal of the detection means.