I develop SBSFU app based on NULEO-L496, I referred to UserApp in 2-images sample. The application can be downloaded, installed and run, but just in a few seconds, the device got rebooted, witch "Reboot triggered by a Watchdog reset!"

[Kevin Lang]

= [SBOOT] System Security Check successfully passed. Starting...

======================================================================

=       (C) COPYRIGHT 2017 STMicroelectronics         =

=                                  =

=       Secure Boot and Secure Firmware Update        =

======================================================================

= [SBOOT] SECURE ENGINE INITIALIZATION SUCCESSFUL

= [SBOOT] STATE: CHECK STATUS ON RESET

     INFO: A Reboot has been triggered by a Software reset!

= [SBOOT] STATE: CHECK NEW FIRMWARE TO DOWNLOAD

= [SBOOT] STATE: DOWNLOAD NEW USER FIRMWARE

     File> Transfer> YMODEM> Send ...

[Kevin Lang]

= [SBOOT] System Security Check successfully passed. Starting...

======================================================================

=       (C) COPYRIGHT 2017 STMicroelectronics         =

=                                  =

=       Secure Boot and Secure Firmware Update        =

======================================================================

= [SBOOT] SECURE ENGINE INITIALIZATION SUCCESSFUL

= [SBOOT] STATE: CHECK STATUS ON RESET

     WARNING: A Reboot has been triggered by a Watchdog reset!

= [SBOOT] STATE: CHECK NEW FIRMWARE TO DOWNLOAD

= [SBOOT] STATE: DOWNLOAD NEW USER FIRMWARE

     File> Transfer> YMODEM> Send ......

[Kevin Lang]

After refresh IWDG, got firewall reset

= [SBOOT] System Security Check successfully passed. Starting...

======================================================================

=       (C) COPYRIGHT 2017 STMicroelectronics         =

=                                  =

=       Secure Boot and Secure Firmware Update        =

======================================================================

= [SBOOT] SECURE ENGINE INITIALIZATION SUCCESSFUL

= [SBOOT] STATE: CHECK STATUS ON RESET

     WARNING: A Reboot has been triggered by a Firewall reset!

= [SBOOT] STATE: CHECK NEW FIRMWARE TO DOWNLOAD

= [SBOOT] STATE: DOWNLOAD NEW USER FIRMWARE

     File> Transfer> YMODEM> Send .........