35.3.1 Initialization

To initialize the OPAMP peripheral for basic, always-on operation, the following steps are recommended:

1. Configure the timebase of the OPAMP peripheral by writing to the Timebase (TIMEBASE) bit field in the Timebase (OPAMP.TIMEBASE) register.
2. For each op amp that will be used:
   1. Configure the Op Amp n Input Multiplexer (OPAMP.OPnINMUX):
      • Select the non-inverting (+) input of the op amp by writing to the Multiplexer for Positive Input (MUXPOS) bit field
      • Select the inverting (-) input of the op amp by writing to the Multiplexer for Negative Input (MUXNEG) bit field
   2. Configure the Op Amp n Resistor Ladder Multiplexer (OPAMP.OPnRESMUX):
      • Select the connection to the top resistor in the resistor ladder by writing to the Multiplexer for Top (MUXTOP) bit field
      • Select the connection to the bottom resistor in the resistor ladder by writing to the Multiplexer for Bottom (MUXBOT) bit field
      • Select the wiper position in the resistor ladder by writing to the Multiplexer for Wiper (MUXWIP) bit field
   3. Configure the Op Amp n Control A (OPAMP.OPnCTRLA) register:
      • Configure the op amp to be always on by writing ‘1’ to the Always On (ALWAYSON) bit
      • Disable events for the op amp by writing ‘0’ to the Event Enable (EVENTEN) bit
      • Select the normal output mode by writing the NORMAL setting to the Output Mode (OUTMODE) bit field
   4. Optional: Configure the allowed settling time by writing to the Settle Timer (SETTLE) bit field in the Op Amp n Settle Timer (OPAMP.OPnSETTLE) register.
3. Enable the OPAMP peripheral by writing a ‘1’ to the OPAMP Enable (ENABLE) bit in the Control A (OPAMP.CTRLA) register.
4. For each op amp whose settling time was configured in step 2.4 above, wait for the SETTLED bit in the Op Amp n Status (OPAMP.OPnSTATUS) register to become ‘1’. This indicates that the op amp start-up and settling have completed, and the OPAMP peripheral is ready for use.