How do you calculate signature of the boot image in LPC4357?

[lpcware]

Content originally posted in LPCWare by crchaves on Sun Feb 22 00:04:16 MST 2015
Hi,

I tried to boot with severals ways the core cortex-M4 without success. Now I try to boot the OS uClinux from the internal flash memory but I need calculate a signature of my bootloader, and I dont know why calculate this kind of checksum.
If anyone has worked with this microcontroller and has installed uClinux successful, I would be grateful with any help


Sincerely,

Cristóbal

[lpcware]

Content originally posted in LPCWare by bavarian on Tue Mar 17 04:46:12 MST 2015
It is just a short checksum over a small area of the flash, in order to tell the bootloader that the content of the flash is valid executable code.
This is described in the UM v1.8 in chapter 6.4.4.1:

"The reserved Cortex-M4 exception vector location 7 (offset 0x001C in the vector table)
should contain the 2’s complement of the check-sum of table entries 0 through 6. This
causes the checksum of the first 8 table entries to be 0. The boot loader code checksums
the first 8 locations in sector 0 of the flash. If the result is 0, then execution control is
transferred to the user code."

That's it, you only need to look at the first 7 words and apply the correct value to the 8th word.

Regards,
NXP Support Team