Excavating
Patent
1987-11-10
1989-07-18
Atkinson, Charles E.
Excavating
371 39, G06F 1110
Patent
active
048499757
ABSTRACT:
A method and apparatus is disclosed for correcting up to two byte errors in encoded uncorrected data in records of a predetermined length. As illustrated, the records are subblocks of a block in a multi-level error correction code format. The data is read from a storage device and corrected by decoding and processing four syndromes of error (S.sub.1, S.sub.2, S.sub.3, S.sub.0) that are generated by means disclosed in the prior art. These syndromes are decoded in response to uncorrected errors in any one record by computing vectors (P, Q, and R), which are functions of the four syndromes. Binary numbers (u and v) are then determined from these vectors by table look-up to enable calculation of one value (d) from the sum of said binary numbers for determining error locations. Another value (t), mathematically related to said one value, is then determined by table look-up and the error location values (y and z) are determined by calculating the offset of binary numbers (u,v) from the other value (t). Finally, error patterns (E.sub.y and E.sub.z) are determined by table look-up.
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Atkinson Charles E.
International Business Machines - Corporation
Otto, Jr. Henry E.
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