31.2.7.22 CRCSUM SFR Description

CRCSUM contains the checksum value. CRCCTRL.PLEN32 controls the checksum size. When selecting CRC-16, bit 16 and above are not used.

The CRC Compare Equation is given by:

Compare is True if CRCSUM = 1.

   CRCSUM = (CRCACC xor CRCFXOR)

Results

Recall as stated in the Overview, that if the comparison fails (CRCSUM = 0), logic sets the CRCERR flag and stops the process by setting the DONE flag.

If no error occurs (CRCSUM = 0):

If AUTOR is not set (calculations only perform once), the CRC logic sets CRCDONE and clears CRCERR. No further checking happens until CRCDONE is cleared and CRCEN is set to load the initial values.

If AUTOR is set (calculations repeat), then the CRC logic reloads all initial settings and restarts the CRC calculation for the next value without setting CRCDONE. Thus CRC checking will be continuously performed until either an error is encountered, or CRCEN is cleared.