2.2.1 Voltage Level Monitoring (VLM)

The VLM, when enabled, monitors the power supply and can be configured to generate an interrupt request when the voltage passes a given threshold. This can act as an early warning to the application that the voltage is passing the VLM threshold and the application can take necessary action to prepare for a possible Brown-out or start-up. The threshold is configurable and is expressed in percentage above the configured BOD level.

The VLM threshold can be configured to:

The VLM can be configured to trigger an interrupt request when:

On FSFEB, the VLM is configured to trigger an interrupt request when the voltage crosses in either direction 15% above the BOD threshold. FSFEB will always start on 0V after a power-up, and when the user sets the voltage above BOD level using the touch slider, the device will start. As soon as the VLM is enabled, the VLM status bit will be set if the voltage is below the VLM threshold. The VLM interrupt will only trigger when the voltage crosses the VLM threshold.

In the VLM interrupt routine, the VLMS bit in the VLM status register is read to determine if the voltage is above or below the VLM threshold. If the VLMS bit is one, the operating voltage is below the threshold and the application heartbeat is increased to indicate this. If the VLMS bit is zero, the operating voltage is above the threshold and the application heartbeat is set to 60 bpm, indicating normal operation.