Encoding of memory cell bit storage having stuck-at faults

摘要

A data storage system includes a memory circuit comprising memory cells and a control circuit. The control circuit generates a first set of redundant bits indicating the bit positions of the memory cells having stuck-at faults in response to a first write operation dependent on whether a first rate or first bit error rate (BER) of the stuck-at faults in the memory cells is greater than a first threshold, for example greater than zero. The control circuit is operable to encode data bits to generate encoded data bits and a second set of redundant bits that indicate a transformation (such as a data inversion) performed on the data bits to generate the encoded data bits in response to a second write operation if a second rate of stuck-at faults in the memory cells is greater than a second threshold. The encoded data bits stored in the memory cells having the stuck-at faults match digital values of corresponding ones of the stuck-at faults. The data storage system may generate a third set of redundant bits indicating which if the first data bits stored in the memory cells having stuck at faults match digital values corresponding to the ones of the stuck at faults in response to the first operation. The memory circuit may operate as a multi-level memory cell and/or may comprise a phase change memory cell.