| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor storage device that can predict an optimum value of a read voltage by using read data, thereby increasing the possibility of correcting errors in comparison with one read operation and in addition, suppressing the occurrence probability of a reoperation when an error correction fails.SOLUTION: A semiconductor storage device includes a controller unit that counts the number of errors included in read data. The controller unit performs both reading at a voltage lower and at a voltage higher than an optimum value of a read voltage; compares the first number of error bits, which is a difference between data read at the lower voltage and data having no errors, and the second number of error bits which is a difference between data read at the higher voltage and data having no errors; and sets, if the first number of error bits is less than the second number of error bits, the optimum value of a read voltage for the next time of data reading so as to be lower than the optimum value of the read voltage of this time. |
