Extended error correction for package error correction codes.

摘要

An extended error code particularly applicable to a code that can correct any number of errors in one sub-field but can only detect the existence of any number of errors in two sub-fields. If the initial pass of the data through the error correction code indicates an uncorrected error, the data is complemented and restored in the memory and then reread. The retrieved data is recomplemented and again passed through the error correction code. If an uncorrected error persists, then a bit-by-bit comparision is performed between the originally read data and the retrieved complemented data to isolate the hard fails in the memory. The bits in the sub-field associated with the hard fail are then sequentially changed and then the changed data word is passed through the error correction code. A wrong combination is detected by the error correction code. The sequential changing continues until the bits in the sub-field associated with the hard fail match the originally stored data, in which case the error correction code can correct the remaining errors in the remaining sub-fields.