27.5.1 Control A

Writing this bit to '1' resets the CRCSCAN peripheral: The CRCSCAN Control registers and STATUS register (CTRLA, CTRLB, STATUS) will be cleared one clock cycle after the RESET bit was written to '1'.

If NMIEN is '0', this bit is writable both when the CRCSCAN is busy (the BUSY bit in CRCSCAN.STATUS is '1') and not busy (the BUSY bit is '0'), and will take effect immediately.

If NMIEN is '1', this bit is only writable when the CRCSCAN is not busy (the BUSY bit in CRCSCAN.STATUS is '0').

The RESET bit is a strobe bit.

When this bit is written to '1', any CRC failure will trigger an NMI.

This can only be cleared by a system Reset - it is not cleared by a write to the RESET bit.

This bit can only be written to '1' when the CRCSCAN is not busy (the BUSY bit in CRCSCAN.STATUS is '0').

Writing this bit to '1' enables the CRCSCAN peripheral with the current settings. It will stay '1' even after a CRC check has completed, but writing it to ‘1’ again will start a new check.

Writing the bit to '0' will disable the CRCSCAN after the ongoing check is completed (after reaching the end of the section it is set up to check). A failure in the ongoing check will still be detected and can cause an NMI if the NMIEN bit is '1'.

The CRCSCAN can be enabled during the internal Reset initialization to verify Flash sections before letting the CPU start normal code execution (see the device data sheet fuse description). If the CRCSCAN is enabled during the internal Reset initialization, the ENABLE bit will read as '1' when normal code execution starts.