JPH04366467A - Bidirectional reading magnetic tape apparatus - Google Patents

Abstract

PURPOSE:To perform a correct reading even when a magnetic tape is read rearward by providing end pattern writing means for writing a predetermined pattern after writing of write data is ended. CONSTITUTION:A write driver 15 writes twice a tape mark on a data block at the last of recording data of a magnetic tape medium 10 to display the last of the data. Immediately after writing of the mark is conducted twice, an end pattern writer 21 is operated to generate a predetermined pattern, which is transmitted to the driver 15, and recorded after a last IBG on the medium. At the time of reading, a magnetic tape 11 initially reads a predetermined pattern 22, and then passes over an IBG (inter block gate). Thus, since a gain of an AGC 13 is sufficient to become constant, even the final block can be stably read.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional read magnetic tape device. In electronic computer systems, magnetic tape devices are used as large-capacity external storage devices, but the disadvantage of magnetic tape devices is that they require a long access time. Therefore, there is a need for a bidirectional read magnetic tape device that is capable of reading in the reverse direction and eliminates rewinding time, and is intended to shorten access time.

0002

2. Description of the Related Art FIG. 3 shows an overview of a data recording format on a conventional magnetic tape medium. In conventional magnetic tape devices, the data recording format recorded on the tape medium is such that there is an IBG (INTER) between data blocks.
BLOCK GAP), and the length of this IBG is 2.0 mm, but only the last IBG length is 1
．． 7mm, and the part behind it is an area with no data (
It was a section with nothing written on it called the NO SIGNAL section. In such a conventional data recording format, there is no problem when reading in the forward direction, but when reading from the last NO SIGNAL section of the magnetic tape in the backward direction, the last There was a problem where data blocks were missed and the second to last data block was read.

FIG. 4 is an explanatory diagram of the operation when reading in the forward direction in a conventional magnetic tape device. In the figure, 11 is a magnetic head that reads data recorded on a magnetic tape medium, 12 is an output amplifier that amplifies the output of the magnetic head 11, and 13 is an automatic gain adjustment circuit that amplifies the output of the output amplifier to a constant amplitude. (Auto Gain
Control: hereinafter abbreviated as AGC), 14 is AG
This is a binarization circuit that binarizes the output of C13.

In FIG. 4, when the data block to be read is A, the output of the magnetic head 11 is amplified while reading a specific pattern indicating the IBG written in the IBG in front of the read magnetic head 11. A to do
The gain of the GC 13 becomes constant, and data block A can be read.

However, there was a problem when reading in the backward direction. FIG. 4B is a diagram when reading is performed in the backward direction. When reading in the backward direction,
When reading the last data from the NO SIGNAL section, even if the read magnetic head 11 passes over the IBG, only the last IBG length is shorter than the others, so the AGC1
Since the gain of 3 is not constant and unstable, the last data block A cannot be recognized as data, and the next data block is read.

FIG. 5 is an explanatory diagram of the characteristics of the automatic gain adjustment circuit. Referring to the diagram, we will explain why data cannot be recognized if AGC is unstable. The AGC function is based on the read waveform (
This is also the output waveform of the output amplifier 12 in FIG. 4) to keep the amplitude constant. When the gain of the AGC is normal, a binarized signal corresponding to the written information is obtained as the output of the binarization circuit 14. In Figure 5 (
b) AGC when the AGC gain is normal
13 and the output of the binarization circuit 14 are shown. If the AGC gain becomes unstable, the amplitude of the readout waveform will vary, and if the AGC gain becomes too high, the waveform may be recognized as a signal when it is actually a noise waveform (
(c) in FIG. 5), conversely, if the AGC gain becomes too low, the actual signal may be regarded as noise ((d) in FIG. 5).

[0007] When reading the last data block in the backward direction, data is read from after a certain pattern of read signals, so if the AGC gain is not constant,
Data cannot be read.

However, when reading the last data block in the backward direction, there is not enough time to keep the AGC gain constant; that is, only the IBG length is 1.7.
mm, which is shorter than the others, so reading is performed while the travel time is short, resulting in a problem that correct reading is not performed.

[0009]

SUMMARY OF THE INVENTION When a magnetic tape is read in the backward direction, there is a problem in that correct reading is not performed when reading the last data block. In view of these points, the present invention provides correct reading even when a magnetic tape is read in the backward direction.
The purpose of this invention is to provide a means for keeping the gain of AGC constant.

0010

[Means for Solving the Problems] The above problems are solved by a bidirectional read magnetic tape device configured as follows. FIG. 1 is a diagram showing the principle of the present invention.

A magnetic head 11 for reading and writing information on a magnetic tape medium 10, an output amplifier 12 for amplifying the output of the magnetic head, and an automatic gain adjustment for amplifying the output of the output amplifier 12 to a constant amplitude. It has a circuit 13 , a binarization circuit 14 that binarizes the output of the automatic gain adjustment circuit 13 , and a write drive circuit 15 that drives the magnetic head 11 .
In magnetic tape devices that read and write information to
By providing an end pattern writing circuit 21 that writes a predetermined pattern after the write data has been written, the predetermined pattern can be written on the magnetic tape medium 10 after the write data has been written, and read in either the forward direction or the backward direction. Configure it so that you can read all the data even if you go there.

0012

[Operation] By providing the end pattern writing means 21 that writes a predetermined pattern after the writing of the write data is completed, the predetermined pattern is written on the magnetic tape medium 10 after the writing of the write data is completed, even when reading from the backward direction. Since a predetermined pattern is written after the final IBG, the AGC operates and normal reading is possible, so all data can be read regardless of whether reading is performed in the forward or backward direction.

[0013]

[Embodiment] In the present invention, in order to solve the problem of reading in the backward direction, a predetermined pattern (a pattern necessary to keep the AGC constant) is written after the last IBG. Allows data blocks to be read.

FIG. 2 is a detailed diagram of an embodiment of the invention. In the figure, 10 is a magnetic tape medium for recording data;
6 is a host device that instructs the magnetic tape device to read and write recording; 15 is a write drive circuit that drives a magnetic head to record information on a magnetic tape medium; and 21 is a write drive circuit that writes a predetermined pattern on the magnetic tape when recording and writing are completed. An end pattern writing circuit 22 is a predetermined pattern recorded after the final IBG. Other components having the same reference numerals as those in FIG. 4 are the same.

First, when writing data, upon receiving a write command and write data from a host device, the magnetic tape device transmits the contents to the write drive circuit 15. The write drive circuit 15 drives a magnetic head according to write data to record on a magnetic tape medium. At the end of recording data on the magnetic tape medium, a tape mark is written twice in the data block to indicate that it is the end of the recorded data. Therefore, it is detected whether or not the tape mark has been written twice, and immediately after the writing of the tape mark has occurred twice, the end pattern writing circuit 21 is operated to generate a predetermined pattern, and the predetermined pattern is transmitted to the write drive circuit 15, and the magnetic Recorded after the last IBG on the tape medium.

[0016] Also, when reading, NO SIGNAL
When reading the last data from the magnetic head 11, the read magnetic head 11 first reads the predetermined pattern 22 and then passes over the IBG. The predetermined pattern 22 needs to include a sufficient number of "1" data to adjust the gain. First read the predetermined pattern 22, then read the IBG
Since the gain of the AGC 13 is sufficient to be constant, even the last data block can be read stably.

[0017]

As is clear from the above description, the present invention has a remarkable industrial effect in that all data blocks can be read even when reading is performed in the backward direction.

[Brief explanation of the drawing]

[Figure 1] Principle diagram of the present invention

[Figure 2] Detailed diagram of the embodiment of the present invention

[Figure 3] Explanatory diagram of data recording format on magnetic tape media

[Figure 4] Diagram explaining read operation of conventional magnetic tape device

[Figure 5] Explanatory diagram of characteristics of automatic gain adjustment circuit

[Explanation of symbols]

10 Magnetic tape medium 11
Magnetic head 12 Output amplifier
13 Automatic gain adjustment circuit 14 Binarization circuit
15 Write drive circuit 16 Host device 21 End pattern writing means or end pattern writing circuit 22 Predetermined pattern

Claims (1)

[Claims] 1. A magnetic head (11) for reading and writing information on a magnetic tape medium (10), an output amplifier (12) for amplifying the output of the magnetic head, and an output of the output amplifier (12). an automatic gain adjustment circuit (13) that amplifies the output of the automatic gain adjustment circuit (13) to a constant amplitude, a binarization circuit (14) that binarizes the output of the automatic gain adjustment circuit (13), and the magnetic head (1
In a magnetic tape device that has a write drive circuit (15) that drives a write drive circuit (15) and reads and writes information to and from a magnetic tape medium (10) according to instructions from a host device (16), after writing of write data is completed, a predetermined By providing an end pattern writing means (21) for writing a pattern,
A bidirectional reading magnetic tape device characterized in that the predetermined pattern is written on a magnetic tape medium (10) after the writing of the write data is completed, and all data can be read regardless of whether the data is read in the forward or backward direction.