A nonvolatile random access memory device includes a plurality of memory cells configured to store data therein, a plurality of reference cells separate from the memory cells, the reference cells each configured to output a corresponding reference cell signal, and a read/write circuit. The read/write circuit is configured to generate from the reference cell signals a reference signal which is variable to have a plurality of different reference levels. The read/write circuit is further configured to identify, in response to the reference signal, a logic state among a first logic state and a second logic state for each of one or more selected memory cells, and to output read data corresponding to the identified logic state.