The BOD settings are loaded from fuses during reset. The BOD level and operating mode in Active and Idle sleep mode are set by fuses and cannot be changed by the CPU. The operating mode in Standby and Power Down sleep mode is loaded from fuses, too, and can be changed by software.

The Voltage Level Monitor function can be enabled by writing a '1' to the VLM Interrupt Enable bit (VLMIE) in the Interrupt Control register (BOD.INTCTRL). The VLM interrupt is configured by writing the VLM Configuration bits (VLMCFG) in BOD.INTCTRL. An interrupt is requested when the supply voltage crosses the VLM threshold either from above, from below, or from any direction.

The VLM functionality will follow the BOD mode. If the BOD is turned off, the VLM will not be enabled, even if the VLMIE is '1'. If the BOD is using sampled mode, the VLM will also be sampled.

The VLM threshold is defined by writing the VLM Level bits (VLMLVL) in the Control A register (BOD.VLMCTRLA).

If the BOD/VLM is enabled in sampled mode, only VLMCFG=0x1 (crossing threshold from above) in BOD.INTCTRL will trigger an interrupt.