JP2564455B2 - Magnetic tape device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reproducing data from a magnetic tape on which a signal is recorded by a helical scan method. A helical scan type magnetic tape storage device can obtain a higher recording density than a fixed head type magnetic tape device, so that it is widely used in a field requiring a large amount of information such as a VTR. It is used. Further, with the recent development of VTR technology, household VTRs have been produced in large quantities at low cost and are about to be widely spread. Therefore, by using the domestic VTR technology, a large-capacity and inexpensive magnetic storage device can be realized. However, the helical scan type VTR is
The recording track is determined by the relative position of the head mounted on the cylinder and rotating, and the magnetic tape running around the cylinder. Therefore, unlike magnetic disk devices and the like, there is a major drawback that random access is not possible. As a storage device of a computer, data reliability is a very important factor. Therefore, in a magnetic disk device such as a flexible disk, when recording data, first record the data to be recorded on the magnetic disk, then reproduce the data to check whether the data is correctly recorded, If something is wrong, it is recorded again. However, the helical scan type VT
In R, since the magnetic tape is running at a constant speed as shown in FIG. 1, the magnetic head automatically moves to the next track, and the recorded data cannot be reproduced for confirmation. When the running of the magnetic tape is stopped, since the recording track is determined by the relative position of the rotating magnetic head and the running magnetic tape, the magnetic head is displaced from the track, and the signal cannot be correctly reproduced. Therefore, in order to reproduce and confirm the data once recorded, it is necessary to rewind the magnetic tape and then run the tape again to reproduce the data. Further, rewinding of the tape and resumption of running are also required for rerecording the recorded data. In general, rewinding and resuming running of tape requires a very long time, and confirmation and re-recording of data in this form is not practical. [0007] As a device using a home VTR,
Convert music signal to digital value and record on VTR P
There is a CM recorder. The PCM recorder is exactly the same as the magnetic tape device in that it records and reproduces digital values. The PCM recorder uses an error correction code in order to improve the reliability of data. But,
The error correction code can correct minor errors but cannot correct severe errors. In the case of an audio signal, even if a serious error occurs at a rate of about once every 30 minutes, it cannot be said to be a fatal error. Therefore, the error correction code is sufficient, and it is necessary to confirm the recorded data. No need. However, when used as an external storage device such as a personal computer, confirmation of recorded data is indispensable because any small error can be fatal. SUMMARY OF THE INVENTION In a helical scan type magnetic tape storage device for recording a digital signal, in order to confirm the recorded data and re-record the data when a recording abnormality occurs as described above. It is necessary to temporarily stop the running of the tape, rewind the tape, and run the tape again at a predetermined speed. An object of the present invention is to provide a highly reliable magnetic tape data reproducing method capable of error-free data reproduction without interrupting normal tape running even when a recording abnormality occurs during data reproduction. Is. A feature of the present invention is that when data is reproduced, correctly recorded data is selected on the basis of information indicating a recording abnormality recorded on the tape. It is configured to be used. According to the present invention, at the time of data reproduction, it is judged whether or not the data is correctly recorded by using the information indicating the recording abnormality recorded on the tape, and only the correctly recorded data is recorded. I have it. 2 and 3 show a recording format and a block diagram of an embodiment according to the present invention, which will be described below with reference to the drawings. Data recording is performed by the first and second recording heads 5 and 7, and data reproduction is performed by the first and second recording heads.
Playback heads 6 and 8 are used. The first and second recording heads 5 and 7 are installed on a cylinder (not shown) on a diagonal line, and the first and second reproducing heads 6 and 8 are also installed on a cylinder diagonal line. There is. The two recording heads 5 and 7 alternately scan the recording tracks, and the two reproducing heads 6 and 8 also alternately scan the tracks. When recording data, the bus line 1
1 is sent to the memory 17 and the encoding circuit 13 through the control circuit 12 that performs an interface operation with the CPU, and the recording signal converted by the encoding circuit 13 is applied to the recording amplifier 14 and the recording head 5.
(Or 7) to record on a magnetic tape. At this time, the reproducing head 6 (or 8) that scans the same track with a slight delay reproduces the signal just recorded,
The reproduction amplifier 15 and the decoding circuit 16 convert the reproduction data. The coincidence detection circuit 18 compares the recording data stored in the memory 17 with the reproduction signal output from the decoding circuit for all tracks. When the recorded data and the reproduced data all match, the data valid signal X is sent to the encoder circuit 13, the recording amplifier 14,
Then, the recording head 7 (or 5) is used to perform recording at the beginning of the next track, and subsequently, data to be recorded next is requested from the CPU side (not shown) and recorded. If the recorded data and the reproduced data do not match, the data invalid signal Y is recorded, and the recorded data stored in the memory 17 is recorded again. Therefore, the tracks on the magnetic tape are recorded as shown in FIG. When the data a is recorded on the track 1 and is correctly reproduced by the reproducing head, the data valid signal X is recorded at the head of the track 2. The following data b is continuously recorded on the track 2. However, although the data c was recorded on the track 3, the reproduction signal is c'for some reason such as a scratch on the magnetic tape. Therefore, the data invalid signal Y is recorded at the beginning of the track 4, and the data c is recorded again at the track 4. When reproducing the data, the reproducing heads 6 and 8 are used to reproduce the data. In this case, if there is the data invalid signal Y, the data before the track is discarded. That is, when the track 4 is reproduced and the data invalid signal Y is reproduced, the data c ′ reproduced on the track 3 is discarded and the data c on the track 4 is used. In the embodiment of FIG. 3, the data valid signal X or the data invalid signal Y is recorded at the beginning of the next track by the recording head 5 or 7, but the reproduction amplifier 15 is used.
And the recording amplifier 14 are temporarily switched, and the reproducing head 6
Alternatively, 8 can be used to record at the end of the track. The tracks on the magnetic tape in this case are as shown in FIG. In the embodiment of FIG. 3, two heads are used for each of the recording head and the reproducing head, but the same can be done by using two heads installed on the diagonal line of the cylinder. In this case, it is necessary to shift the setting of one head as compared with the other head and adjust so that the two heads scan the same track. As described above, according to the present invention, error-free data reproduction can be performed without interrupting normal tape running even when a recording abnormality occurs during data reproduction. The necessary processing also determines whether the data is normal,
If it is not normal, only the data of the next track is used, so it can be easily processed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an example of a recording format of a helical scan type magnetic tape storage device. FIG. 2 is an explanatory diagram showing a recording method according to the present invention. FIG. 3 is a block diagram showing an embodiment of a magnetic tape data reproducing method according to the present invention. FIG. 4 is an explanatory diagram showing recording tracks according to the present invention. FIG. 5 is an explanatory diagram showing a recording track of another embodiment according to the present invention.

Continued front page    (56) References JP-A-48-82812 (JP, A)                 JP-A-53-10412 (JP, A)                 JP-A-55-142406 (JP, A)

Claims (1)

(57) [Claims] 1. When data is recorded by the helical scan method and the data is not recorded normally, re-record the data and record the flag data indicating the recording error on the same magnetic tape as the recording data. Is a method of reproducing data from a magnetic tape recorded
Then , when the flag data is detected during reproduction, the data reproduction method of the magnetic tape, wherein the already reproduced data corresponding to the flag data is invalidated.