A device is disclosed that includes memory cells, a reference circuit, and a sensing unit. Each of the memory cells is configured to store bit data. The reference circuit includes reference switches and reference storage units. The reference switches are disposed. A first reference storage unit of the reference storage units is configured to generate a first signal having a first logic state when a first reference switch the reference switches is turned on. A second reference storage unit of the reference storage units is configured to generate a second signal having a second logic state when a second reference switch of the reference switches is turned on. The sensing unit is configured to determine a logic state of the bit data of one of the memory cells according to the first signal and the second signal.