In USB DFU and PCIe boot modes, the
boot image is processed in image mode, meaning that the image is entirely loaded in
internal RAM at address 0x70001000 before the certificate is validated.
This introduces two limitations compared to the other boot modes:
- Once the image is validated,
it needs to be relocated by the DMSC to its final location to be ready for
execution. Since the source and destination for the copy are both in
internal RAM, the user needs to ensure the reloaction address is either in a
lower address (0x70000000-0x71000000) or in a higher address beyond the end
of the image (0x71000000 + size of image). If this is not followed, the
image relocation will corrupt itself while copying, resulting in a boot
failure. The relocation address is defined in the certificate.
- Because the downloaded image is at offset 0x70001000 it also means that
both DFU and PCIe maximum image size are 4Kbytes less than with the other
boot mode.