16.5.7 Device Fuse Integrity Check

As described in Boot ROM Operating Modes, the Boot ROM performs fuse integrity checks automatically upon any type of reset. This behavior is always enabled and does not require any user configuration.

If the user has programmed the sequence numbers (SEQ0 and SEQ1) using the Microchip-provided Firmware Metadata (FWMD) Generator Tool, the Boot ROM uses these values to determine the preferred boot configuration between BOOTCFG1 and BOOTCFG1A.

The fuse integrity check process follows this sequence:

  1. The Boot ROM reads SEQ0 and SEQ1 to determine the user preferred boot configuration.
  2. It performs an integrity check on the selected BOOTCFG fuse set.
  3. If the selected fuse set fails the integrity check, the Boot ROM automatically attempts to boot using the redundant BOOTCFG fuse set.
  4. If both fuse sets fail integrity checks, the Boot ROM halts the boot process and places the device into a known safe state called interactive mode,
Note: If the boot process fails due to fuse integrity check failure, the Boot Failure Signal (configured through BOOT_GPIOSEL) is not asserted.
Figure 16-6. USERCFG1/1x fuse Integrity Check Selection