Nonvolatile semiconductor memory device having structure storing multivalued data and data storage system comprising the nonvolatile semiconductor memory device

摘要

The inventive flash memory comprises a memory cell array including nonvolatile memory cells and a control CPU controlling data writing, reading and erasing in the memory cell array and a multivalued flag part. The multivalued flag part stores a value indicating whether data written in any memory cell is binary data or multivalued data. The data can be read in a binary read sequence for the binary data or a multivalued read sequence for the multivalued data due to the value of the multivalued flag part.