5.5 BOOTCFG - Boot Configuration Fuses

The BOOTCFG fuses contain configuration details for the device and essential peripherals, such as BOD or WDT, that are applied after a device reset and during start-up.

When the Sequence Number (SEQNUM) fuse is not 0xFFFFFFFF at start-up and after a Reset, the contents of the other BOOTCFG fuses are copied to the respective peripheral registers and bit fields, as described in the following fuse descriptions. Follow these steps to alter the device configuration:
  1. Write the desired values to the fuses.
  2. Reset the device. The values are copied from the fuses to the peripheral registers.
  3. (Optional) To read the actual configuration, read the respective registers of the SYSCTRL, WDT, and SUPC.
Attention: When the SEQNUM fuse is not 0xFFFFFFFF, all of the BOOTCFG fuse values are copied to the peripheral registers. For this reason, all BOOTCFG fuses must be written to desired values—the factory values of these fuses have no practical meaning.

When the value of the Sequence Number (SEQNUM) fuse is equal to 0xFFFFFFFF, none of the BOOTCFG fuse values are copied to any of the peripheral registers at startup/reset. Instead, the respective reset values given in the peripheral registers’ descriptions are used.

Note: The entire BOOTCFG section is unaffected by the Chip Erase command. For this reason, the residual space of the BOOTCFG section (after the Fuses described below) can be used to store persistent application data, such as serial numbers or application keys.