| 摘要 |
PURPOSE:To simplify the correction of data by preparing an initial memory area where the partial correction is impossible for the data written into a read- only memory ROM and a patch area having a high degree of reading preference and therefore just writing only the corrected data into a patch area at correction of data. CONSTITUTION:In an initial memory area 51 the data written into a ROM cannot be corrected unless the data is erased. A patch area 52 can use an address in common to a part of the area 51 and has a reading preference degree higher than the area 51. When the initial data is stored in such an EPROM, the area 52 is set in an access unable state and the initial data is stored in the area 51. When the partial correction is desired for the initial data, the correction data is written into the area 52 after this area 52 is set in an access enable state. Thus the initial data is stored and kept as it is in the area 51, and only the correction data is stored in the area 52. As a result, the correction of data is simplified. |
