| 摘要 |
<p>PROBLEM TO BE SOLVED: To elongate a life by setting a reference nonvolatile memory of an inferior characteristic to a nonvolatile memory in a memory cell array and controlling on the basis of the reference result of the reference nonvolatile memory to raise a reference level at a read operation of a sense amplifier which is stored beforehand in a predetermined address area of the nonvolatile memory. SOLUTION: Every time a read operation to a nonvolatile memory in a memory cell array is repeated, a read operation is also conducted to a reference nonvolatile memory 40 connected to an equal word line. When data in the reference nonvolatile memory 40 is detected to be deleted while the read operation is sequentially repeated, a reference voltage of a sense amplifier 43 is changed via a control circuit 44. Since the reference voltage at the read operation of the sense amplifier 43 is controlled to be raised, a judge criterion by the sense amplifier is loosened and a life of the nonvolatile memory 40 which causes a read failure can be extended.</p> |
