Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
2000-10-06
2003-08-26
Decady, Albert (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
Reexamination Certificate
active
06611939
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a data error correction device which executes iterative decoding of multiply added error-correcting codes, in data processing.
BACKGROUND ART
Conventionally, data error correction devices which decode error-correcting codes having capabilities of correcting data errors are utilized in various data recording/reproduction apparatus, as a method for increasing the reliabilities of data processing systems.
Particularly in recent years, due to the high density recording to recording media or increased data transfer rate for the data processing apparatus, the probability of errors in data which are read from the recording media is increased. Accordingly, plural error-correcting codes each having a high error-correcting capability are added to the data, or iterative decoding in which the plural error-correcting codes are repeatedly decoded is performed in the data error correction device.
For example in CD-ROMs, an error-correcting code for music CD which is called CIRC and another two kinds of error-correcting codes are added to data. Further, the iterative decoding is performed for these two kinds of error-correcting codes. Similarly, also in DVD-ROMs or DVD-RAMs, the iterative decoding is performed for product codes.
Generally, when data are read from a recording medium to be transferred to the data processing apparatus, it is required that the demodulation processing, error correction processing, data transfer processing and the like should be executed without delaying the reading of the data. Accordingly, the data error correction device is designed to satisfy the requirements also when performing the iterative decoding of a predetermined number of times successively.
FIG. 3
is a block diagram illustrating a structure of a prior art data error correction device.
In the figure, numeral
31
denotes a syndrome calculation means for calculating a syndrome of input data. Numeral
32
denotes an error location
umeric value calculation means for calculating an error location and an error numeric value on the basis of the syndrome calculated by the syndrome calculation means
31
. Numeral
33
denotes an uncorrectability detection means for detecting the presence or absence of uncorrectable codewords in the present decoding. Numeral
34
denotes a correction termination judgement means for judging the termination of the correction process. Numeral
35
denotes a control means for controlling the syndrome calculation means
31
, the error location
umeric value calculation means
32
, the uncorrectability detection means
33
and the correction termination judgement means
34
. In addition, numeral
130
denotes a data error correction device which comprises the syndrome calculation means
31
, the error location
umeric value calculation means
32
, the uncorrectability detection means
33
, the correction termination judgement means
34
, and the control means
35
.
Here, the error-correcting codes (code A and code B) are doubly added to the input data, respectively.
FIG. 4
is a flowchart showing an example of procedures of the iterative decoding which is repeated a predetermined number of times in the data error correction device as shown in FIG.
3
.
FIG. 5
is a flowchart showing an example of procedures of the decoding which is repeated less than the predetermined number of times in the data error correction device as shown in FIG.
3
.
In
FIGS. 4 and 5
, the error-correcting codes which are doubly added, respectively, are the code A and the code B. A
1
decoding, B
1
decoding, A
2
decoding and B
2
decoding show the first decoding of the code A, the first decoding of the code B, the second decoding of the code A and the second decoding of the code B, respectively. That is, these figures show the processing in which the code A and the code B are alternately subjected to the iterative decoding twice, respectively. In addition, UNC(B
2
)=0 shows that no uncorrectable codeword is detected in the B
2
decoding. When UNC(B
2
) is not 0, i.e., it is 1, it shows that the uncorrectable codeword is detected. The same things can be said of UNC(A
1
), UNC(B
1
and UNC(A
2
) in FIG.
5
.
Initially, the case (Prior Art 1) where error judgement is made by the iterative decoding of the predetermined number of times in the data error correction device is described with reference to
FIGS. 3 and 4
.
(Step S
1
) The syndrome calculation means
31
receives from outside the data to which the error-correcting codes, i.e., code A and code B are doubly added as described above, then calculates a syndrome of the code A which is added to the input data, and outputs the syndrome.
Then, the error location
umeric value calculation means
32
calculates the error location and error numeric value of the code A from the syndrome calculation means
31
on the basis of the syndrome calculated by the syndrome calculation means
31
and outputs these values to the outside as well as outputs the values calculated by the error location
umeric value calculation means
32
to the uncorrectability detection means
33
.
Then, the uncorrectability detection means
33
detects the presence or absence of uncorrectable codewords in the present decoding (A
1
decoding) from the values calculated by the error location
umeric value calculation means
32
, and outputs the detection result.
Then, the correction termination judgement means
34
outputs a judgement result that the next B
1
decoding is to be executed to the control means
35
, regardless of the detection result of the uncorrectability detection means
33
, i.e., regardless of the presence or absence of uncorrectable codewords.
Then, the error correction processing in the A
1
decoding is terminated.
(Step S
2
) Next, the control means
35
controls the syndrome calculation means
31
and the like, whereby the next B
1
decoding is executed.
The syndrome calculation means
31
calculates a syndrome of the code B which is added to the input data and outputs the syndrome. The error location
umeric value calculation means
32
, the uncorrectability detection means
33
and the correction termination judgement means
34
operate in the same manner as in the above-mentioned A
1
decoding (step: S
1
), and then the B
1
decoding is terminated.
(Step S
3
) Then, also in the A
2
decoding, the syndrome calculation means
31
, the error location
umeric value calculation means
32
, the uncorrectability detection means
33
and the correction termination judgement means
34
operate in the same manner as in the above-mentioned B
1
decoding (step S
2
), and then the error correction processing is terminated.
(Step S
4
) Then, also in the B
2
decoding, the syndrome calculation means
31
, the error location
umeric value calculation means
32
and the uncorrectability detection means
33
operate in the same manner as in the above-mentioned A
2
decoding (step S
3
), and a detection result showing the presence or absence of uncorrectable codewords in the last decoding (B
2
decoding) is output.
(Step S
5
) Then, the correction termination judgement means
34
receives the detection result (UNC(B
2
)) from the uncorrectability detection means
33
, and judges the termination of the correction processing (iterative decoding).
When the detection result is UNC(B
2
)=0 and shows that no uncorrectable codeword is detected, the correct termination judgement means
34
judges that all errors in the data are corrected, and outputs the judgement result that the correction is to be terminated to the control means
35
. The control means
35
controls the syndrome calculation means
31
and the like, to execute the iterative decoding for data which are to be subjected to the error correction processing next, without interruption.
Inversely, when the detection result is UNC(B
2
)=1 and shows that the uncorrectable codeword is detected, the correction termination judgement means
34
judges that errors remain in the data, and outputs a judgement result judging the uncorrectability to the control means
35
.
Abraham Esaw
De'cady Albert
Matsushita Electrical Industrial co., Ltd.
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