Patent ID: 7881111

Claim:
A nonvolatile memory apparatus comprising: a nonvolatile memory; and a control unit for controlling writing data and reading data to or from the nonvolatile memory, wherein the nonvolatile memory includes plural memory cells, each of which is for storing plural bits of data therein by shifting a threshold voltage thereof to one of plural threshold voltage ranges, wherein, in performing a first page writing, the threshold voltage of a first memory cell of said plural memory cells remains in a first threshold voltage range or shifts into a second threshold voltage range in accordance with data to be written into the first memory cell, wherein, in performing a second page writing, the threshold voltage of the first memory cell remains in the first threshold voltage or the second threshold voltage, or shifts into a third threshold voltage range from the first threshold voltage range or into a fourth threshold voltage range from the second threshold voltage range, and wherein a second memory cell of said plural memory cells is configured to be used for storing information indicating whether the first page writing or the second page writing is performed on the first memory cell.