EH_STATE Features

  • EH_STATE allows for fast device startup by not employing the hardware Root of Trust in the system.
  • The boot process bypasses the application authentication steps, performing only cursory checks on the application before trying to execute it.
  • This state also allows some level of debug port locking; the user can specify a 128-bit key that is stored in NVM.
    • This key, once present, is used by the ROM to enforce the debug port locking functionality.
    • Once a device is locked, the debug port can only be accessed by the provision of the key through the Data Exchange Unit (DEU).
  • The state also allows for a specific SOC ID to be written to each device, which can be read back at a later stage by the DEU if required.
    • This enables device manufacturers to identify their devices uniquely if needed.
    • The SOC ID in EH mode is a 32-bit value. For more detail about the SOC ID, see Setting the SOC ID.