S32K3: Fast standby exit with HSE initialization

[Verifono]

On a trigger the S32K3 shall wake-up from standby, send a CAN message and receive a response - all within 50 milliseconds. The response is an CMA authenticated message (CAN message authentication).

'Fast standby exit' is used to bypass secure boot, otherwise the 50 milliseconds cannot be kept. My understanding is that the HSE (Hardware Security Engine) ist not initialized and its functionality is not available when using 'fast standby exit' - is that correct? However, the HSE is needed for the message authentication.

How can this be solved? Secure boot with flash verification is not wanted after the wakeup. Only the HSE must be initialized so that it can povide its services to the application software.

[VaneB]

Hi @Verifono 

From the images below, you can see that the program can only choose whether to use fast wakeup or not:

As HSE is only booted from the sBAF, this will only be available after a Reset or Normal Standby Exit. So you can not initialize it after a Fast Standby Exit as this skips the sBAF and secure boot section.

B.R.

VaneB