| 摘要 |
<p>PURPOSE:To use effectively an original read-only memory ROM contents in case of function change or the like by providing an auxiliary area, where data is not written initially, on the ROM in relations preliminarily determined with respect to address and using control information, which indicates whether a cell is effective or not, stored in a part of the cell. CONSTITUTION:A part of every cell is used as a keyword (control informatiin) 21,...2N in a table 1, and the table 1 consists of plural cells 31,...3N which are not arranged in order and an auxiliary area 4 following the cell 3N in prescribed relations with respect to address. If a prescribed bit pattern is in the write state in every keyword, it means that the cell corresponding to this keyword is effective to fulfill a specific function obtained by fractionizing the function asigned to the table 1; but if all bits of the keyword are in the write state, it means that the cell corresponding to this keyword is ineffective not to fulfill the specific function.</p> |
