NXP Semiconductors K32 L2A Series, Reference Manual, Page: 318 / 1379

• The MMCAU information structure and the actual MMCAU functions do not need to
be in contiguous memory.
• A ready-to-use library contains these functions, but this library needs to be rebuilt to
be compatible with the prototypes above. Specifically, the rcon variable needs to be
passed into the functions, to make the code relocatable.
After an encrypted SB file starts to be received by the bootloader, the information for
setting up the MMCAU is retrieved and the decryption process begins.
• If the information is incorrect or if the functions do not meet the above requirements,
then the bootloader can become unresponsive, so be sure that everything is correctly
implemented as above.
• If there is a recoverable error, then the bootloader will return a relevant error code.
If everything is operating properly, then the exact same response will be received as
though the bootloader was receiving an unencrypted file via the ReceiveSbFile command.
14.7 Verifying the application in flash using CRC-32
Using CRC-32 and a given address range, the ROM bootloader supports performing an
application integrity check.
Before application integrity testing: the following fields in the bootloader configuration
area must be set:
• Set crcStartAddress to the start address that should be used for the CRC check.
• Set crcByteCount to the number of bytes to run the CRC check on, from the start
address.
• Set crcExpectedValue to the value that the CRC calculation should result in.
Application integrity testing:
• If all of the above fields are unset (all 0xFF bytes for crcStartAddress, crcByteCount,
and crcExpectedValue), then the ROM bootloader returns
kStatus_AppCrcCheckInvalid.
• If any one of the above fields are set (crcStartAddress, crcByteCount, and
crcExpectedValue), then the ROM bootloader checks if the given address range of
the application is valid, and if the application resides in internal flash or external
QSPI flash, by running a CRC check on the image in flash:
• If the the given address range of the application is not valid (false), then the
bootloader returns kStatus_AppCrcCheckOutOfRange.
• If the given address range of the application is valid (true), then the CRC check
is performed. The CRC32 algorithm in ROM uses a polynomial
(0x04C1_1DB7), and the initial seed is 0xFFFF_FFFF.
Verifying the application in flash using CRC-32
K32 L2A Reference Manual, Rev. 2, 01/2020
318 NXP Semiconductors