| 摘要 |
PURPOSE:To easily set the protecting information to an unused area by inhibiting the accesses to the unused area excepting those used for preventive maintenance. CONSTITUTION:In an initialization, an initializing part 11C of a processor 1 starts an unused protecting information setting part 112 and sets the unused protecting information PZ within a protecting information setting part 13 in response to all unit areas Aij of a memory 2. When the processor 1 gives an access to the memory 2 for purposes excepting the preventive maintenance, a normal access part 14 refers to the part 13 and decides the access abnormality in case protecting information Pk is equal to the information PZ. When an access is given to the memory 2 for the purpose of preventive maintenance, a security access part 15 refers to the part 13 and has no access and returns only the result showing that a normal access is carried out in case the information Pk is coincident with the information PZ.
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