| 摘要 |
PURPOSE:To decide whether the operation of a memory is possible or not at each time of access by storing information classification data correspondingly to addresses and reading out this data at the time of memory access from a processor to compare it with operation classification information from the processor. CONSTITUTION:Information classification data indicating address area information of the memory is read out from an information classification storage part 4b and is stored in an information classification register 6. Meanwhile, a processor 1 sends operation classification data indicating the classification of instruction read or data read/write together with an address and data information at the time of accessing the memory and stores this operation classification data in an operation classification register 5. A deciding circuit 7 compares stored data of registers 5 and 6 to decide whether the access operation is possible or not. Consequently, the erroneous access to an unused area or the memory access to destroy the contents of an instruction area or a read-only data area is immediately detected. Thus, the safety of the system is improved.
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