| 摘要 |
PURPOSE:To make it impossible to read data unless the prescribed conversion rules are used by converting data or their addresses with the prescribed rules beforehand when the data are stored in a ROM. CONSTITUTION:In a ROM of a ROM control circuit 2, data, which have been converted according to the prescribed conversion rules determined beforehand at the time of storing data, are stored at respective corresponding addresses. Moreover, these addresses have been converted according to the prescribed conversion rules. It is assumed that an address value and data values are made correspond to positive logic and negative logic for every bit according to the prescribed rules. Consequently the address value and data values in the ROM control circuit 2 will not become effective information even when these values are read by hardware. |
