LPC55S69: PUF reinitialization

[EugeneHiihtaja]

Hi !

In case of Secure Boot, few keys can be loaded to PUF in Boot-Rom and etc.

So it is appears in my code in some preprogrammed state.

After that in my code I'm using lowpower PowerDown mode what deinitialize PUF to some level.

If I  call PUF_Init/Start after that, PUF reinitalized and I can execute Key/Keycode Set/Get operations without visible problems.

But Init function have PUF reset RESET_SetPeripheralReset(kPUF_RST_SHIFT_RSTn);

and also manipulate with PUF clock.

But from other side I can't see in fsl_puf any special API for partial re-initialization for cases when Secure Boot enabled.

Do I understand right and in my firmware I can manipulate with PUF freely (deinit/init/start) and etc, even secure boot is fully enabled and some intrinsic keys are loaded ?

Or what kind of other sequences I should use to reinitialize PUF after PowerDown mode ?

Regards,

Eugene

[diego_charles]

Hi Eugene,

You are correct,  your application can make use of the PUF deinit/init/start commands freely.  They should not affect

 the Key codes stored in the protected flash region.

After a power down wake you will  need to initialize the module again and wait until becomes ready. Then if you have a previously stored activation code you can perform start command ,skipping enroll operation.

Regards,

Diego,