Abstract: Data is stored in a multi-level MRAM (MLC MRAM) cell in a manner that reduces transition states that require high energy. A new data block is received, and the new data block is divided into one or more sub-groups of bits, with each sub-group comprising at least two bits. Each sub-group is assigned data bit locations in a memory store. The received bits are compared with sub-groups present at the data bit locations to determine subgroups of hot bits. For each subgroup of hot bits, an encoding flag value is determined by XORing their most significant bits. The most significant bits of each subgroup of hot bits are complemented and the encoding flag is SET. A data block is generated to establish a data group for each subgroup of hot bits including the subgroup of hot bits and the encoding flag for that subgroup.

Abstract: The odd/even invert coding for phase change memory with thermal crosstalk devises a cost model that captures Phase Change Memory (PCM) SET/RESET write asymmetries, as well as write disturbs caused by thermal crosstalk. The cost is computed by counting the different types of transitions between the old and the new data to be written to PCM. An Odd/Even Invert data encoding/decoding algorithm makes intelligent decisions based on a cost model by taking into account the number of bit flips, write asymmetry, as well as write disturbs. The data encoding algorithm recodes the data on the fly based on selective inverting (even, odd, or full invert) to search for a minimum cost solution with aim at reducing write activities and extending the PCM lifetime. A hardware architecture for the present encoding/decoding algorithm is presented that requires only two bits storage overhead for coding, regardless of the width of data.