1. A memory unit comprising; a substrate; an interface unit formed to the substrate; first and second non-volatile memory chips formed to the substrate; and a memory management unit formed to the substrate and connected to the first and second non-volatile memory chips and the interface unit, the memory management unit comprising, an access unit reading data from a memory area of the non-volatile memory chip at reading, and wiring data to the memory area of the non-volatile memory chip at wiring, wherein the non-volatile memory chip is swappable when another non-volatile memory chip is operating.