Patent ID: 6631485
Filing Date: 2003-10-07
Classification: G11B

Abstract:
Apparatus for storing a stream of data records on magnetic media, said apparatus including:group formatting means for grouping said data records into groups of data bytes; sub-group processing means for dividing each of said groups into sub-groups, wherein each sub-group comprises data bytes corresponding to one or more data tracks; a track checksum calculating means for applying the data bytes from each said data track to a checksum algorithm to calculate one or more checksums for each data track, means for transforming each sub-group into at least one respective array, each corresponding to a data track, first error correction coding encoding means for encoding columns of each array to provide first ECC codewords comprising data bytes and parity bytes for causing first level correction of at least one of the data bytes in said first EEC codewords; second error correction coding encoding means for encoding rows of each array to provide second ECC codewords comprising data bytes and parity bytes for causing second level correction of at least one of the data bytes in said second ECC codewords, and wherein the data bytes and parity bytes making up any given second ECC codewords are in accordance with at least one predetermined ECC rule; the algorithm applied by said track checksum calculating means being such that it does not correlate with said predetermined ECC rule but is arranged to provide a checksum having the property that, on decoding of said ECC codewords and re-calculating and checking of the track checksum, the probability of a miscorrected codeword causing a track checksum failure is increased.