Semiconductor device and its memory access control method

A memory access control method performed in semiconductor device, wherein the semiconductor device comprises:

• a main-arithmetic unit configured to execute a program;
• a sub-arithmetic unit configured to execute a process of a part of the program executed by the main-arithmetic unit, the sub-arithmetic unit including a register configured to store an access permission range address value provided from the main-arithmetic unit;
• and
• a shared memory configured to be accessed by the main-arithmetic unit and the sub-arithmetic unit,
• the memory access control method comprising:
• the sub-arithmetic unit executing a predetermined process according to an operation instruction provided from the main-arithmetic unit;
• and
• the sub-arithmetic unit providing, among access requests issued to the shared memory according to the predetermined process, an access request for an address within an access permission range specified by the access permission range address value to the shared memory and blocking an access request for an address outside the access permission range specified by the access permission range address value;
• wherein the main-arithmetic unit executes, as the program, a reliability-verified program having a high reliability and a reliability-unverified program having a reliability lower than that of the reliability-verified program, and a process for storing the access permission range address value into the register of the sub-arithmetic unit is performed by the reliability-verified program.