6.10 Configuration and User Fuses (FUSE)
Fuses are part of the nonvolatile memory and hold the device configuration. The fuses are available from the device power-up. The fuses can be read by the CPU or the UPDI but can only be programmed or cleared by the UPDI. The configuration values stored in the fuses are written to their respective target registers at the end of the start-up sequence.
The fuses for peripheral configuration (FUSE) are pre-programmed but can be
altered by the user. Altered values in the configuration fuse will be effective only
after a Reset.
Note: When writing the
fuses, all reserved bits must be written to ‘1’.