A dynamic random access memory (DRAM) with code bit and self-refresh operation is disclosed. In one particular exemplary embodiment, at least one code bit is appended to N bits of user data to form a new code data. The user data are stored in a plurality of user data sub-arrays and code bit is stored in code bit sub-array respectively. Each sub-array stores at least one bit per user-specified row and column address. Each sub-array is independently controlled in either refresh operation or user operation.Refresh operation works on at least one sub-array at a time out of a plurality of sub-arrays. User operations work on other sub-arrays out of a plurality of sub-arrays. User read operation and internal refresh operation can work concurrently.