The Cyclic Redundancy Check (CRC) is an important safety feature. It scans the Nonvolatile Memory (NVM) making sure the code is correct.
The device will not execute code if Flash fault has occurred. By ensuring no code corruption has occurred, a potentially unintended behavior in the application that can cause a dangerous situation can be avoided. The CRC scan can be set up to scan the entire Flash, only the boot section, or both the boot and application code sections.
The CRC generates a checksum that is compared to a pre-calculated one. If the two checksums match, the Flash is OK, and the application code can start running.
The BUSY bit in the Status (CRCSCAN.STATUS) register indicates if a CRC scan is ongoing or not, while the OK bit in the Status (CRCSCAN.STATUS) register indicates if the checksum comparison matches or not.
The CRCSCAN can be set up to generate a Non-Maskable Interrupt (NMI) if the checksums do not match.