8.10.2 Write Fuses

The fuses may only be "programmed," that is, written from one to zero. The write fuses operation is allowed only after successfully presenting the secure code (Write 7 password). The fuses must be blown sequentially: FAB must be blown first, CMA may be blown only if FAB is zero, and PER only if CMA is zero. After this command, the host must perform ACK polling. The SEC fuse is blown at the Microchip factory to protect lot history information.