| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a semiconductor memory which has nonvolatile memory cells and can reliably and correctly read the stored information without increasing the chip size. <P>SOLUTION: The bit lines connected to nonvolatile memory cells are connected to a comparator 105 through a bit line selector circuit 104 controlled by the bit line selector circuit driver 103. It compares the discharge potentials of the bit lines with the predetermined reference value in the comparator 105, and counts the discharge periods where the discharge potential is larger than the reference value in the counter 106 based on the output data from the comparator 105. It detects the threshold between information 0 and information 1 from the distribution of the counts of the counter 106 for the memory cells connected to one bit line, and discriminates the stored information in the memory cells based on this threshold. Since conventional reference cells can be eliminated, the chip size can be reduced, and discrimination errors due to the variations of the memory cells or temporal changes of retained charges are prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
