A key difference between C28-based devices and the F29H85x is the integration of the Hardware Security Module (HSM). The HSM is a subsystem that provides security and cryptographic functions. The C29 CPUs interface with the HSM to perform cryptographic operations required for code authentication, secure boot, secure firmware upgrades, and encrypted run-time communications.

During the flash boot sequence, the HSM is responsible for authentication of image present in flash. For the authentication to succeed, the programmed image must include an X.509 certificate. The post-build steps of the project are responsible for generating a valid X.509 certificate. Please refer to this section for details on the post-build steps.

The HSM introduces the concept of different device security states. The device states are High Security - Field Securable (HS-FS), High Security - Key Provisioned (HS-KP), and High Security - Security Enabled (HS-SE). By default, the F29H85x device ships with HS-FS. Table 1-1 describes the differences between these three states.

The FOTA upgrade process differs between HS-FS and HS-SE devices. For details regarding the C29 CPU1/CPU3 FOTA upgrades on an HS-FS device, refer to the High-Level Flow section.

For details regarding C29 CPU1/3 or HSM FOTA upgrades on an HS-SE device, refer to the Secure Firmware Upgrade section of the TIFS SDK (tifs_f29h85x_xx_xx_xx_xx/docs/api_guide_f29h85x/html/docs_src/secure_firmware_update/secure_firmware_update.html)