| 摘要 |
PROBLEM TO BE SOLVED: To prevent a program from being executed by preventing program data from being modified without an output data part 24 and a code storage part 26 even when restoring only the program data. SOLUTION: An arithmetic unit 28 of an output data processing part 24 included in a program ROM calculates low-order four bits D0 to D3 of first program data read from a program data storage part and address arithmetic codes d0 to d3 of four bits set in a code storage part 26 included in the same program ROM, and outputs arithmetic results D0' to D3'. A selector 30 substitutes the D0' to D3' for D0 to D3, thus the output data processing part 24 outputs second program data of total eight bits of the DO' to D3' +D4 to D7. |
