Data recording/reproducing apparatus

Abstract: In a data recording/reproducing apparatus (1) which can record/reproduce digital data, since a parity check code (C1, C2) is added to data at the time of recording the data (D), the original data (D) can be reproduced by error correction even though part of the data is lost at the time of reproducing. In the present invention, in order to improve reliability of data (D) still more, the data (D) immediately after recorded is read and the number of errors in it is detected by means of its parity check code (C1,C2) at the time of recording data (D), and in case that the number of errors in the data is equal to or greater than a predetermined reference value, the data is re-recorded. Therefore, by setting the reference value at a value less than the maximum number of errors which can be corrected by means of parity check codes (C1,C2), data is also re-­ recorded which has apprehension that it cannot be corrected due to increase of the number of errors in it caused by deterioration of its recording state owing to repetition of a reproducing operation on the like. In this way, reliability of the data recording/reproducing apparatus (1) can be remarkably improved.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data recording/reproducing apparatus such as a rotary head type digital audio tape recorder (hereinafter referred to as R-DAT) and the like which can perform recording/reproducing of digital data. 2. Description of the Prior Art Up to now, there has been a magnetic recording/reproducing apparatus such as an R-DAT and the like which can reproduce from data a part of which is lost its original data through error correction in reproduction, by adding some error correction information (such as a parity check code) to the original data in case of recording digital data on a magnetic tape. Although such an apparatus can correct completely data of which very little part is lost, it cannot reproduce the original data in case that part of the data has been lost over a wide range. In case of using such a magnetic recording/reproducing apparatus as an auxiliary storage of a computer or the like, it is necessary to check a recording state of data after recorded, in order to detect such a situation as this. For example, therefore, writing heads and reading heads are separately provided and inspection of recorded data is performed by a method called "read after write", namely, a method of reproducing with a reading head data written on a magnetic tape by a writing head immediately after writing the data to compare it with its original data. Reliability of data is improved by writing data again when any write error has been detected in the data through inspection of the recorded data by the above-mentioned comparison method and the like. This method is known, for example, from Patent Abstracts of Japan, vol. 9, no. 113 (P-356) (1836) May 17, 1985, (Matsushita D.S.K.K.). This document discloses further a magnetic recording and reproducing device which records the same data on one track and also the adjacent track for error correction at reproduction, or in case if a difference exists between data reproduced by reading the original data and the original data. Furthermore, it is known from Patent Abstracts of Japan, vol. 10, no. 101 (P-447) (2158) April 17, 1986, (Sony K.K.) to judge whether the data needs to be written again or not in an alternate sector. The judgement is based upon a check whether write data is recorded correctly by reading out the written data and deciding on its error state. This document is considered to represent the closest prior art. EP-A-0278702 discloses an apparatus for reproducing a digital signal (Fig. 4) comprising two rotary magnetic heads, both heads for reproducing data recorded on a magnetic tape, whereby data has to be stored on the tape according to a PCM data format used for rotary head digital audio tape recorders, said data including error correction codes. The apparatus is adapted to reproduce recorded data without the use of a recorded tracking signal. Generally, an R-DAT performs an azimuth recording by means of two magnetic heads which have their azimuth angles different from each other. It can, therefore, record data in high density by overlapping contiguous tracks on each other. For this reason, a reading head is positioned so that it can reproduce data from the narrow tracks. In case of tracing a track immediately after recording data on it by means of such a reading head as this, since a track for data to be next recorded on it has not been formed yet, the reading head reproduces data from the wide track. Since a level of reproducing signal is too high at this time, tracing position of the reading head needs to be shifted slightly. Since inspection of recorded data in such an R-DAT as mentioned above is performed by a method of comparing data corrected through error correction information with its original data, it has been impossible to detect a data recording state quantitatively. When repeating a reproducing operation of a magnetic tape multiple times, its recording state is deteriorated due to rubbing between the magnetic tape and the reading head, and the like. There is a case, therefore, that error correction becomes impossible due to increase of errors after a plurality of reproducing operations even though error correction immediately after recording can correct every error. SUMMARY OF THE INVENTION An object of the present invention is to provide a data recording/reproducing apparatus which can solve the above-mentioned problem and record and/or reproduce data in high reliability and speed. The data recording/reproducing apparatus according to the invention comprises the features of appended claim 1. According to the invention, in a data recording/reproducing apparatus which adds error correction data for detecting errors in main data to the main data to be recorded and records such data in each predetermined unit recording area on a recording medium by means of a recording means, data immediately after recorded is reproduced by a reading means at the time of recording data and detection of errors in the main data on the basis of its error correction data is performed by an error detecting means. The number of errors in the main data is counted for each unit recording area by means of a counting means, and the original of data in which the number of errors is equal to or greater than a predetermined reference value is recorded in another unit recording area. In this way it is possible to detect a data recording state quantitatively, and inspection of the recording state can be easily performed. And data in a unit recording area in which the number of errors is equal to or greater than the above-mentioned reference value, namely, data in a unit recording area in which a recording state is bad is re-recorded. Additionally, by setting the reference value at a value less than the maximum number of errors which can be corrected by error correction data, the data is also re-recorded which has apprehension that it cannot be corrected due to increase of the number of errors in it caused by deterioration of its recording state owing to repetition of a reproducing operation and the like even though its every error can be corrected immediately after recorded. In this way, reliability of a data recording/reproducing apparatus can be remarkably improved. BRIEF DESCRIPTION OF THE DRAWINGS These objects, the other objects, features, and merits of the present invention will be clarified more expressly by the following detailed descriptions and drawings. Fig. 1 is a block diagram showing basic configuration of an R-DAT1 of an embodiment of the invention, Fig. 2 is a diagram showing configuration of data to be recorded on a magnetic tape 3, Fig. 3 is a diagram showing a recording pattern of the magnetic tape 3 on which data are recorded, and Fig. 4 is a flowchart to explain a recording operation of the R-DAT1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, a preferred embodiment of the present invention is described in details below. Fig. 1 is a block diagram showing basic configuration of an R-DAT1 of an embodiment of the invention. The embodiment uses the R-DAT1 as an auxiliary storage of an external computer 2. In case of recording data from the external computer 2 on a magnetic tape 3, the external computer 2 gives data to an interface 4 as well as gives a data recording instruction to a control unit 5 through the interface 4. The data is output to a recording signal processing circuit 7 as well as output to a memory 6 of random access memory and the like from the interface 4. Input and output operations and the like in the interface 4 are performed according to control signals from the control unit 5 implemented by a microcomputer and the like. In the recording signal processing circuit 7, error correction codes and the like in DAT are added to the data in each frame. The frame is a recording area consisting of two tracks formed respectively by recording heads W1 and W2 described later. Fig. 2 is a figure showing configuration of data and their error correction codes to be recorded in one frame. Data of one frame consist of data D to be recorded in a recording area 21, first error correction codes C1 which are vertical parity check codes to be recorded in a recording area 22, and second error correction codes C2 which are horizontal parity check codes to be recorded in a recording area 23. Addition of error correction codes is started with addition of the first error correction codes C1. The first error correction codes C1 (0,0) to C1 (ℓ,0) are added to the data D (0,0) to D (m,0), and in the same way the first error correction codes C1 (0,1) to C1 (ℓ,1) through the first error correction codes C1 (0,n) to C1 (ℓ,n) are respectively added to the data D (0,1) to D (m,1) through the data D (0,n) to D (m,n). In this way the first error correction codes C1 of the n+1 columns have been added to the data. Next, the second error correction codes C2 are added to the data D and the first error correction codes C1, respectively. The second error correction codes C2 (0,0) to C2 (0,k) are added to the data D (0,0) to D (0,n), and in the same way the second error correction codes C2 (1,0) to C2 (1,k) through the second error correction codes C2 (m,0) to C2 (m,k) are respectively added to the data D (1,0) to D (1,n) through the data D (m,0) to D (m,n). And the second error correction codes C2 (m+1,0) to C2 (m+1,k) through the second error correction codes C2 (m+ℓ+1,0) to C2 (m+ℓ+1,k) are respectively added to the first error correction codes C1 (0,0) to C1 (0,m) through the first error correction codes C1 (ℓ,0) to C1 (ℓ,n). In this way the second error correction codes C2 of the m+ℓ+2 rows have been added. Signals of the data to which the first and second error correction codes C1 and C2 were added in this way are modulated in order to be recorded on the magnetic tape 3 and supplied to a recording signal amplifier 11. The data signals amplified by the recording signal amplifier 11 are recorded on the magnetic tape 3 by the recording heads W1 and W2 mounted on a rotary drum 12. Such recording heads W1 and W2, and reproducing heads R1 and R2 described later are fixed on the rotary drum 12 of circular cylinder type. The rotary drum 12 is rotated in the direction of an arrow 13 by a motor (not shown in the Fig.1). The magnetic tape 3 is run in the direction of an arrow 14 by a capstan 9 and a pinch roller 10. At this time a capstan driving means 8 controls the capstan 9 according to a control signal from the control unit 5. As shown in Fig. 3, the recording heads W1 and W2 form respectively tracks Ai and Bi (i=1,2,...) as tracing in the direction of an arrow 18 on the magnetic tape 3 being run in this way. The track Ai, which is a portion recorded by the recording head W1, is reproduced by the reproducing head R1. The track Bi, which is a portion recorded by the recording head W2, is reproduced by the reproducing head R2. Each data is recorded in a frame Fi consisting of one pair of tracks Ai and Bi. Data recorded on the magnetic tape 3 are reproduced by the reproducing heads R1 and R2. The reproducing heads R1 and R2 reproduce data respectively on the tracks Ai and Bi formed by the recording heads W1 and W2 individually corresponding to the reproducing heads R1 and R2. Signals from the reproducing heads R1 and R2 are amplified by a reproducing signal amplifier 15 and supplied to a reproducing signal processing circuit 16. In the reproducing signal processing circuit 16, error correction and the like are performed by means of the first and second error correction codes C1 and C2 added in the recording signal processing circuit 7. In inspection of a recording state immediately after recording at the time of recording, a quantity called syndrome is calculated, using the second error correction codes C2. That is to say, using the second error correction codes C2 (0,0) to C2 (0,k) through the second error correction codes C2 (m,0) to C2 (m,k), syndromes of the data D (0,0) to D (0,n) through the data D (m,0) to D (m,n) are calculated, and using the error correction codes C2 (m+1,0) to C2 (m+1,k) through C2 (m+ℓ+1,0) to C2 (m+ℓ+1,k), syndromes of the first error correction codes C1 (0,0) to C1 (0,n) through the first error correction codes C1 (ℓ,0) to C1 (ℓ,n) are calculated. Calculation of these syndromes makes it possible to detect the number of errors and location where they occur. A syndrome is calculated for each data unit of one row. In case that an error is found in the reproduced data, a pulse signal is supplied to a counter 17 from the reproducing signal processing circuit 16. Each time calculation of syndromes of one frame portion, namely, syndromes of the m+ℓ+2 rows which is performed by means of the second error correction codes C2 is finished, the reproducing signal processing circuit 16 supplies a reset signal to the counter 17. The counter 17 is reset by the reset signal, counts the number of errors for each frame on the basis of the pulse signals, and supplies the count value to the control unit 5. The control unit 5 compares the count value of the counter 17 with a predetermined reference value, and re-records the data when the count value is equal to or greater than the predetermined reference value. Fig. 4 is a flowchart to explain a recording operation of the R-DAT1. At step n1, data from the external computer 2 are inputted and at step n2, the data are recorded on the magnetic tape 3. At step n3, the recorded data are reproduced immediately after recorded and at step n4, their syndromes are calculated by the reproducing signal processing circuit 16. At step n5, it is decided whether or not the number of errors is equal to or greater than the reference value, and in case that the number of errors is less than the references value, the recording operation is returned to step n1 and the next data are inputted. In case that the number of errors is equal to or greater than the reference value, the recording operation proceeds to step n6 and inputting of data from the external computer 2 is stopped. At step n7 then, the data are read from the memory 6 and at step n8 the data are re-recorded. At step 11 the recorded data are reproduced immediately after recorded and at step n10 their syndromes are calculated in the reproducing signal processing circuit 16. At step n11, it is decided whether or not the number of errors in the data is equal to or greater than the reference value, and in case that the number of errors is less than the reference value, the recording operation is returned to step n1 and the next data from the external computer 2 are inputted. In case that the number of errors is equal to or greater than the reference value, the recording operation is returned to step n7 and the re-recording operation is performed again. The above-mentioned operation is concretely described below as referring to Fig. 3. Immediately after the data D1 is recorded in the frame F1, the data D1 is reproduced and its recording state is inspected. In case that the number of errors in the reproduced data D1 is equal to or greater than the reference value, the data D1 is re-recorded. At this time the data D1 is re-recorded in the frame F4, since data D2 and D3 are recorded respectively in frames F2 and F3 while the recording state of the data D1 is being inspected. According to the embodiment of the invention as mentioned above, since a recording state of data can be detected quantitatively, inspection of the recording state of the data immediately after recorded can be easily performed. And by selecting as the reference value a number less than the maximum number of errors which can be corrected by means of the first and second error correction codes C1 and C2, it is possible to keep data re-recorded which have apprehension that they cannot be corrected due to increase of the number of errors in them caused by a plurality of reproducing operations even though they can be corrected immediately after they were recorded. In this way, when the R-DAT1 is used as an auxiliary storage of the external computer 2, its reliability as the auxiliary storage can be remarkably improved.

Claims: A data recording/reproducing apparatus, comprising: a recording means (W1, W2) for recording first main data (D1) in a first unit recording area (F1) of a recording medium (3) and for adding error correction data (C1, C2) to the main data (D1) in the first unit recording area (F1); a reading means (R1, R2) for reading the recorded data from the first unit recording area (F1) immediately after the data is recorded, the reading means (R1, R2) being disposed in close vicinity of the recording means (W1, W2); an error detecting means (16) for detecting errors in the main data on the basis of the error correction data (C1, C2); and a counting means (17) for counting a number of errors on the basis of the output of the error detecting means (16), whereby when the number of errors counted in the recorded data of the first unit recording area (F1) is equal to or greater than a predetermined reference value, the apparatus is adapted to re-record the recorded data into a second unit recording area (F4), characterized in that the apparatus is adapted to record the main data (D2 to D3) which follows the first main data (D1) in a third unit recording area (F2 to F3) being adjacent to and following said first unit recording area (F1), while error detection of the first main data (D1) is accomplished, and said second unit recording area (F4) being adjacent to and following said third unit recording area (F2 - F3). A data recording/reproducing apparatus as claimed in claim 1 wherein the error correction data (C1,C2) consists of a vertical parity check code (C1) of the first error correction code and a horizontal parity check code (C2) of the second error correction code. A data recording/reproducing apparatus as claimed in claim 1 wherein the error detecting means (16) calculates a syndrome which indicates the number of errors and location where they occur for each unit data row, using at least one of the first and second error correction codes (C1,C2).

Inventors: KIYONAGA CHITOKU, SUDOH KENGO, KIYONAGA, CHITOKU, SUDOH, KENGO
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1990
Main classification: G11B20
IPC codes: G11B20