20.3.1 Initialization

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

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

The VLM functionality will follow the BOD mode. If the BOD is disabled, the VLM will not be enabled, even if the VLMIE is ‘1’. If the BOD is using the Sampled mode, the VLM will also be sampled. When enabling the VLM interrupt, the interrupt flag will always be set if VLMCFG equals 0x2, and may be set if VLMCFG is configured to 0x0 or 0x1.

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