| 摘要 |
PURPOSE:To simplify a change over means and reduce a capacity of a defective cell address storing ROM by changing over the defective cell to a redundant cell group in an unit of a line of matrix or a column constituted by H, V parity system. CONSTITUTION:A redundant cell of one bit per a selecting word line is not prepared but the redundant cell group of one column of one line of a matrix prepared by an ECC circuit of H, V parity systems is prepared, and RC is its redundant cell group. When a cell MCj on a word line WL makes a hard error, all the cells of the (j) column including the cell are replaced by the redundant cell group RC. In such a manner, it is not required to judge whether the hard error cell MCk is included in the line and the column including a cell to be made access MCi or not but the cell group of the (j) column of this word line may be simply replaced by the redundant cell group RC, so that the change over control becomes easy and a circuit construction is simplified.
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