Method and system for correcting long bursts of consecutive errors

Claim 1

A method of correcting multibyte errors in a magnetic medium on which data is recorded in variable length blocks that comprise subblocks of data bytes and corresponding check bytes and include error correction code (ECC) for which ECC syndromes are generated during reading, said method comprising the steps of: writing at the end of each block a sequence of N sequential parity check bytes; during reading, after the generation of the ECC syndromes, generating parity syndromes by comparing the parity check bytes computed from the data bytes and check bytes as read with the parity check bytes as written; in response to a long-burst error condition, generating a pointer to the first of the N consecutive bytes in a block that could have been influenced by the error burst; using any ECC syndromes which are not affected by the N bytes identified by the pointer, correcting correctable errors in all subblocks not affected by these identified bytes; adjusting the parity syndromes according to the errors thus corrected; using the adjusted parity syndromes, correcting the errors in the N bytes indicated by the pointer; adjusting an unused ECC syndromes according to the errors corrected by the adjusted parity syndromes; and using the adjusted ECC syndromes, correcting all correctable errors then remaining.

Claim 2

A method of correcting multibyte errors in a magnetic medium on which data is recorded in variable length blocks that comprise subblocks of data bytes and corresponding check bytes and include error correction code (ECC) for which ECC syndromes are generated during reading, said method comprising the steps of: writing at the end of each block a sequence of N sequential parity check bytes; during reading, after the generation of the ECC syndromes, generating parity syndromes by comparing the parity check bytes computed from the data bytes and check bytes as read with the parity check bytes as written; in response to a long-burst error condition, generating a pointer to the first of the N consecutive bytes in a block that could have been influenced by the error burst; using any ECC syndromes which are not affected by the N bytes identified by the pointer, correcting correctable errors in all subblocks not affected by these identified bytes; adjusting the parity syndromes according to the errors thus corrected; using the adjusted parity syndromes, correcting the errors in the N bytes indicated by the pointer; adjusting an unused ECC syndromes according to the errors corrected by the adjusted parity syndromes; and using the adjusted ECC syndromes, correcting all correctable errors then remaining.

Claim 8

A method of correcting multibyte errors in a magnetic medium on which data is recorded in variable length blocks that comprise subblocks of data bytes and corresponding check bytes and include error correction code (ECC) for which ECC syndromes are generated during reading, said method being operable to correct up to a preselected number of errors in each subblock during processing at a first level of error correction and additional errors in each block during processing at a second level of error correction, said method comprising the steps of: writing at the end of each block a sequence of N sequential parity check bytes to create N parity groups from interleaved data bytes and check bytes; during reading, after the generation of the ECC syndromes, generating during first level correction parity syndromes by comparing the parity check bytes computed from the data bytes and check bytes as read with the parity check bytes as written; in response to a long-burst error condition, generating a pointer to the first of the N consecutive bytes in a block that could have been influenced by the error burst; using any ECC syndromes which are not dependent on the N bytes identified by the pointer, correcting any correctable errors during first level correction; adjusting the parity syndromes according to the errors thus corrected; using the adjusted parity syndromes, correcting the long-burst errors in the N bytes indicated by the pointer; adjusting any unused first level ECC syndromes according to the errors corrected by the adjusted parity syndromes; and using the adjusted first level ECC syndromes, correcting all first level correctable errors; adjusting second level ECC syndromes for all errors thus far corrected; and using the adjusted second level ECC syndromes, correcting all correctable errors then remaining.

Claim 9

A method of correcting multibyte errors in a magnetic medium on which data is recorded in variable length blocks that comprise subblocks of data bytes and corresponding check bytes and include error correction code (ECC) for which ECC syndromes are generated during reading, said method being operable to correct up to a preselected number of errors in each subblock during processing at a first level of error correction and additional errors in each block during processing at a second level of error correction, said method comprising the steps of: writing at the end of each block a sequence of N sequential parity check bytes to create N parity groups from interleaved data bytes and check bytes; during reading, after the generation of the ECC syndromes, generating during first level correction parity syndromes by comparing the parity check bytes computed from the data bytes and check bytes as read with the parity check bytes as written; in response to a long-burst error condition, generating a pointer to the first of the N consecutive bytes in a block that could have been influenced by the error burst; using any ECC syndromes which are not dependent on the N bytes identified by the pointer, correcting any correctable errors during first level correction; adjusting the parity syndromes according to the errors thus corrected; using the adjusted parity syndromes, correcting the long-burst errors in the N bytes indicated by the pointer; adjusting any unused first level ECC syndromes according to the errors corrected by the adjusted parity syndromes; and using the adjusted first level ECC syndromes, correcting all first level correctable errors; adjusting second level ECC syndromes for all errors thus far corrected; and using the adjusted second level ECC syndromes, correcting all correctable errors then remaining.