Derived ECC for Protection of On-Demand Data

Traditional error correction coding (ECC) methodologies store data parity bits along with data they protect. Subsequently, upon accessing the combined data and parity bits it is possible discover and correct faults in either the data or correction bits. In domain-wall memories (DWMs), a type of sequential access non-volatile memory related to spin-transfer torque magnetic memory (STT-MRAM), it is not convenient or efficient to store data to protect access errors data shifting during sequential access. To solve this problem, we propose a new technique called derived error correction (DEC) for such cases where it is intractable to record metadata for error correction. Instead, we rebuild the metadata on-demand and store only the parity bits that protect the metadata. The DWM metadata is constructed using a novel transverse read (TR). TR reads in an orthogonal direction of a traditional DWM access point and can be used to calculate number of ones in a DWM. Faults in the metadata correspond to shift-errors in the DWM. Using ECC, we can correct these faults in the metadata and use these corrections to repair the shifting state of the DWM to ensure correct operation. Through these techniques, we propose a shift-aware error correction code that provides a lifetime over 10 years while reducing area by 2.6 and 3.7 times against state of the art technique