| 摘要 |
PURPOSE:To make the reading of the content of ROM difficult and to prevent the leakage of know-how and a secret item by converting a part of or all data transmitted from a second storage means to a micro processor so that they can be inversely converted in accordance with a value which a first storage means holds. CONSTITUTION:The micro processor 1 transmits address information for reading a program to ROM 4 through a signal line 101. ROM 4 transmits data corresponding to a transmitted address on a signal line 103 and transmits it to a conversion circuit 2. The circuit 2 converts data transmitted from the signal line 103 by a conversion rule which is instructed by a non-volatile register 3 and transmits it to the micro processor 1 through a signal line 102 as program information. Program information written into ROM 4 at that time is stored in a shape where original program data is inversely converted in accordance with the conversion rule. Thus, it becomes difficult for a third person to decode and analyze the program and the outflow of know-how and the leakage of secrecy can be prevented. |
