The CRC can run in these modes:

Although the CPU has priority under the continuous mode and single mode in the background, there can still be a "collision". Therefore, the CPU will have to wait one additional cycle when this condition occurs. It is important that it should not run continuous background checks during executing or running safety critical code. Otherwise, it is hard to get test coverage.

The CRC fetches a new word (16-bit) on every third main clock cycle when in priority mode, or when the CRC module is set to do a scan from startup. In background mode, scan time can not be guaranteed.