US Patent 11170868 Semiconductor memory devices and memory systems

A semiconductor memory device includes a memory cell array and an interface circuit including an error correction code (ECC) engine. The memory cell array includes a plurality of volatile memory cells, a normal cell region and a parity cell region. The interface circuit, in a write operation, receives main data and first parity data from an external device, the first parity data being generated based on a first ECC and stores the main data in the normal cell region and the first parity data in the parity cell region. The interface circuit, in a read operation, performs an ECC decoding on the main data using a second ECC, based on the first parity data to correct a first type of error in the main data. The second ECC has a parity check matrix which is the same as a parity check matrix of the first ECC.