System and method for correcting errors in coded data recorded in blocks and sub-blocks

摘要

The present invention relates to an error correcting system for correcting errors in coded data recorded on a record medium in blocks of data bytes, in which each block comprises at least one sub-block, of data bytes and at least one sub-block error check byte (C1 to C3), and at least one block error check byte. The system is of the type which comprises error syndrome byte generating means, responsive to the error check bytes recorded in each sub-block, for generating, during read out of the data bytes and error check bytes in each sub-block, error syndrome bytes, and error correcting means, responsive to the error syndrome bytes, for correcting errors in the data bytes read out from each of the sub-blocks.;A system according to the invention is characterised in that it comprises;first error syndrome byte generating means for generating sub-block error syndrome bytes, corresponding to the check bytes associated with each sub-block,;first error syndrome processing circuitry (73), responsive to the sub-block error syndrome bytes, to detect and correct a predetermined number of errors in the data bytes in each sub-block and to detect but not correct another predetermined number of errors in the data bytes in each sub-block,;additional block error check byte generating means (72B) for generating additional block error check bytes (CO) for each block, corresponding to uncorrected errors in any sub-block in each block,;second error syndrome byte generating means for generating additional block error syndrome bytes, corresponding to the error check bytes in each block and the additional block error check bytes, and;second error syndrome processing circuitry (74 - 78), responsive to the block error syndrome bytes, to correct additional errors in the data bytes in each block.