| 摘要 |
PROBLEM TO BE SOLVED: To prevent using a cell which has high possibility of becoming defective in the future by judging the normal/defective state of a cell on the basis of the absolute value of a resistance value of each memory cell. SOLUTION: Average values of bit line potential at the time of read of a desired plurality of cells in a high resistance state are obtained previously, and they are stored in a reference voltage generator 62. At the time of read, the reference voltage generator 62 outputs voltage in which voltage of half of resistance variation by data scheduled at the time of design is added to this average value, a discriminator 61 compares this value with a bit line potential read via transistors 58, 59. In judging the normal/defective state of cells, all cells are set in the high resistance state, the reference voltage generator 62 outputs voltage of 105% of the average value, the discriminator 61 discriminates the cell as defect when the bit line potential at the time of read is higher than this potential. COPYRIGHT: (C)2004,JPO
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