OEM Firmware Ratchet Level

  • Only MB1-BCT is ratchet protected using hardware fuses.
  • Fuses are field programmable and can be updated when the device is in the field.
  • The ratchet value is thermometer encoded (a numerical value between 0 to N). For example, the number of bits set from LSB denotes the ratchet value.
  • Besides MB1-BCT, all OEM owned firmware loaded during boot are ratcheted using their absolute ratchet value in MB1-BCT.
  • OEM owned firmware ratchet versions are set in MB1-BCT and their corresponding BCH during flashing or offline image creation. For more information, see Bootburn.

For more details, see Ratchet Fuse Programming for OEM Owned Software Components.