MEMORY ACCESS CONTROL CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a memory access control circuit capable of obtaining a high protection function against an illegal access. SOLUTION: A register 14 stores the value of a program counter 11. A table 15 stores the addresses of a protection area in a memory and a table 16 stores the address of an instruction allowed to access to the protection area. An access detection circuit 17 judges whether an instruction is an access instruction to the protection area or not as the decoding result of the instruction based on a compared result between an accessed address and an address in the table 15. At the time of detecting an access instruction to the protection area, a comparator circuit 18 mutually compares the addresses of the register 14 and the table 16, and at the time of judging an instruction read out from an area inhibited from accessing to the protection area, outputs an inhibition signal to inhibit an illegal memory access.