8.5.1 Region Descriptor

Each protection region x has a region descriptor comprised of four SFRs: Control (PRxCTRL), Start Address (PRxST), End Address (PRxEND) and Lock (PRxLOCK). Most region descriptor register bit/field Reset values can be configured with Configuration bits (FPRxCTRL, FPRxST and FPRxEND).

Region descriptor configuration options include dynamic configuration by firmware, static configuration by boot firmware and permanent configuration using fuses. This last option enables creating permanent OTP and IRT regions in program Flash that cannot be modified even with a chip erase. Firmware configurable region descriptors also include a locking mechanism. The PRxLOCK register must be configured to allow descriptor writes; otherwise, writes to other descriptor registers are ignored.