JPH0561612A - Magnetic tape controller - Google Patents

Abstract

PURPOSE:To prevent the writing of error data generated due to a failure of an internal circuit in a magnetic tape control device in a magnetic tape, to quickly detect the failure of the internal circuit and to improve the reliability of the control device. CONSTITUTION:At the time of writing, write data transferred from a master device 20 are modulated to a write format in the magnetic tape by a writing circuit 1 and the modulated data are compressed by a data compressing circuit 2 in accordance with regulated algorithm and sent to a magnetic tape device 30. A selector 6 selects a write data bus 5 connected from the circuit 1 under control by a main control part 7 and inputs the selected bus 5 to a reading circuit 3, which sends the input data to a data extending circuit 4 to check whether the compressed data formed by the circuit 2 can be correctly extended in accordance with the regulated algorithm or not. At the time of reading, read data sent from the device 30 are inputted to the circuit 3 through the selector 6 and extended by the circuit 4 and then the extended data are transferred to the device 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape controller, and more particularly to a write / read data compression technique.

[0002]

2. Description of the Related Art Conventionally, a magnetic tape controller of this type is
When writing, the data sent from the host device is compressed by the data compression circuit and sent to the magnetic tape device. When reading, the compressed data read from the magnetic tape device is expanded by the data expansion circuit and sent to the host device. There is.

[0003]

As described above, the conventional magnetic tape control device does not have a function of detecting an error when a failure occurs in the data compression circuit, and therefore, the erroneous compressed data is directly recorded on the magnetic tape. Since it is sent to the device and recorded on a tape, this error is detected and noticed only at the time of reproduction, and it takes time to deal with the error and the reliability of the magnetic tape control device is reduced.

An object of the present invention is to provide a write data bus for directly inputting the output of the write circuit to the read circuit,
By inputting the compressed data output from the data compression circuit to the data expansion circuit at the time of data writing, the above-mentioned drawbacks are eliminated, and incorrect data written to the magnetic tape due to a circuit failure inside the magnetic tape control device can be written. It is an object of the present invention to provide a magnetic tape control device that can be prevented in advance, at the same time can detect an internal circuit failure promptly, and can improve the reliability of the magnetic tape control device.

[0005]

A magnetic tape controller according to the present invention compresses write data transferred from a host device according to a predetermined algorithm, and a compressed data compressed by the data compression circuit. In a magnetic tape controller having a data expansion circuit that expands compressed data during a read operation from a written magnetic tape device, the compressed data output from the data compression circuit is input to the data expansion circuit when writing data.

[0006]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram of a magnetic tape controller according to an embodiment of the present invention.

In FIG. 1, a magnetic tape controller 10
Is a write circuit 1 that controls writing of write data transferred from the host device 20 onto the magnetic tape, a data compression circuit 2 that compresses the write data, and read data sent from the magnetic tape device 30. Controlled host device 2
0, a read circuit 3 for transferring data to 0, a data expansion circuit 4 for expanding compressed read data, a selector 6 for directly inputting write data to the read circuit 3, and a main control unit for controlling the operation of the entire apparatus. 7 and 7.

Next, the overall operation of the magnetic tape controller of this embodiment will be described. At the time of writing, write data transferred from the host device 20 is modulated by the write circuit 1 into a write format on the magnetic tape, compressed by the data compression circuit 2 according to a prescribed algorithm, and sent to the magnetic tape device 30. .. Then, the write data bus 5 from the write circuit 1 is selected by the selector 6 under the control of the main control unit 7 and input to the read circuit 3.
The input data is sent to the data decompression circuit 4, and it is checked whether the compressed data generated by the data compression circuit 2 can be decompressed without error according to a prescribed algorithm. On the other hand, at the time of reading, the read data sent from the magnetic tape device 30 is input to the read circuit 3 through the selector 6. Further, the data is expanded by the data expansion circuit 4, and then transferred to the higher-level device 20. Next, a specific operation of the magnetic tape controller of this embodiment will be described. The write data transferred from the host device 20 is modulated by the write circuit 1 into a write format on the magnetic tape and sent to the data compression circuit 2. It is assumed that the data compression circuit 2 fails to generate compressed data according to the specified algorithm. Then, the validity of the illegal compressed data is not recognized by the data compression circuit 2 itself, the write circuit 1, and the magnetic tape device 30, and is recorded on the magnetic tape as it is. At the time of writing, the main controller 7 selects the write data path 5 from the write circuit 1 by the selector 6, so that the incorrect compressed data is sent to the magnetic tape device 30 and at the same time input to the read circuit 3. The illegal compressed data input to the read circuit 3 is sent to the data decompression circuit 4 and attempts to decompress the data in accordance with a prescribed data decompression algorithm. However, since the compressed data is incorrect, the correct data is not expanded, and the incorrect expanded data is sent to the read circuit 3. The decompressed data input to the read circuit 3 is recognized by the main control unit 7 as illegal decompressed data. As a result, the main control unit 7 causes the data compression circuit 2
Or if an abnormality is detected in the data expansion circuit 4,
It reports to the host device 20 that the data recorded on the magnetic tape is incorrect.

[0010]

As described above, the magnetic tape control device of the present invention has the write data bus for directly inputting the output of the write circuit to the read circuit, and the compressed data output from the data compression circuit at the time of writing the data. By inputting to the data decompression circuit, it is possible to prevent erroneous data from being written to the magnetic tape due to a failure of a circuit inside the magnetic tape control device, and at the same time, detect an internal circuit failure promptly. Therefore, there is an effect that the reliability of the magnetic tape control device can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a magnetic tape controller according to an embodiment of the present invention.

[Explanation of symbols]

 1 write circuit 2 data compression circuit 3 read circuit 4 data decompression circuit 5 write data bus 6 selector 10 magnetic tape control device 20 host device 30 magnetic tape device

Claims (1)

[Claims] 1. A data compression circuit for compressing write data transferred from a host device according to a predetermined algorithm, and a read operation from a magnetic tape device in which the compressed data compressed by the data compression circuit is written. A magnetic tape controller having a data expansion circuit for expanding compressed data, wherein the compressed data output from the data compression circuit is input to the data expansion circuit when writing data.