26.6.5 Programmable Low Voltage Detector

The programmable LVD is able to monitor the VDDIO input power supply.

Before enabling the LVD by setting LVD.ENABLE bit, the threshold level bits field (LVD.LEVEL) and the direction (LVD.DIR) have to be configured. The LVD register is Enable-Protected, meaning that it can only be written when the LVD is disabled (LVD.ENABLE). As long as the Enable bits is ‘1’, any writes to LVD register will be discarded and a bus error will be generated. The Enable bits are not Enable-Protected.

Settling Time

After being enabled, a start-up delay is required before the result of the comparison is ready. During the startup-time, the output value is zero (STATUS.LVDET).

After the start-up time has passed, the LVDET ready bit is set (STATUS.LVDRDY) indicating that STATUS.LVDET bit is available, and the appropriate LVD interrupt flag or output event are also generated. New comparisons are performed continuously until LVD.ENABLE bit is written to zero. The start-up time applies only to the first comparison. If LVD is disabled (LVD.ENABLE is written to 0), the STATUS.LVDRDY bit will take time to fall because of resynchronization. As a consequence, this is forbidden to re-enable immediately the LVD if the STATUS.LVDRDY field is still one.

LVD Interrupt and Event

• LVD Output Interrupt source: LVD Output interrupt source status (STATUS.LVDET) is set to one when the VDDIO voltage value crosses the programmed threshold level (LVD.LEVEL) in the right direction (LVD.DIR). It is reset to zero when the VDDIO voltage value crosses the threshold level in the wrong direction (LVD.DIR). Note that if the LVD is just enabled and the voltage is already below the threshold (if DIR=1) or the voltage is already above the threshold (if DIR=0), then the LVD output interrupt is also generated.

• LVD Output event: The LVD can generate output event when the VDDIO voltage value crosses the programmed threshold level (LVD.LEVEL) in the right direction (LVD.DIR). To enable this feature, the LVD.OEVEN bit has to be set to one. Refer to the EVSYS Event System for details on configuring the event system.

LVD Behavior in Sleep Mode

LVD is off in hibernate and backup sleep modes.

LVD is automatically turned OFF in standby mode except if the LVD.RUNSTDBY bit is set.