| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a compact and user-friendly storage device that has a large storage capacity in a simple structure. <P>SOLUTION: The storage device has: a semiconductor nonvolatile memory storing multiple bits in each memory cell; a semiconductor volatile memory; a controller part for accessing the semiconductor nonvolatile memory and semiconductor volatile memory; a power supply detection circuit; a voltage holding circuit; and a power supply switch control circuit. In the semiconductor nonvolatile memory, a plurality of addresses corresponding to the multiple bits are assigned to each memory cell to provide a plurality of page modes corresponding to the plurality of addresses, and a save area and a data area are allocated as storage areas. Save data is written to the semiconductor nonvolatile memory at power shutdown only in the first page mode corresponding to the least significant bit. <P>COPYRIGHT: (C)2010,JPO&INPIT |
