To enable a CRC in software (or via the debugger):
- Write the MODE and Source (SRC) bit
fields of the Control B register (CRCSCAN.CTRLB) to select the desired mode and
source settings.
- Enable the CRCSCAN by writing a '1'
to the ENABLE bit in the Control A register (CRCSCAN.CTRLA).
The CRCSCAN can be enabled during the internal reset initialization to ensure
the Flash is OK before letting the CPU execute code. If the CRCSCAN fails during the
internal reset initialization, the CPU is not allowed to start normal code execution. The
full source settings are available during the internal reset initialization. See the Fuse
description for more information.
If the CRCSCAN was enabled during the internal reset initialization, the CRC
Control A and B registers will reflect this when normal code execution is started:
- The ENABLE bit in CRCSCAN.CTRLA will
be '1'
- The MODE bit field in CRCSCAN.CTRLB
will be BACKGROUND
- The SRC bit field in CRCSCAN.CTRLB
will reflect the checked section(s).