US Patent 10115446 Spin transfer torque MRAM device with error buffer

A nonvolatile error buffer is added to STT-MRAM memory design to reduce the error correction coding ECC required to achieve reliable operation with a non-zero Write Error Rate (“WER”). The error buffer is fully associative, storing both the address and the data of memory words which have failed to write correctly within an assigned ECC error budget. The write cycle includes a verify to determine if the word has been written correctly. The read cycle includes a search of the error buffer to determine if the address is present in the buffer.