39.6.2.2 Enabling, Disabling and Resetting
The SDADC is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The SDADC is disabled by writing a zero to CTRLA.ENABLE.
The SDADC is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the ADC will be reset to their initial state, and the SDADC will be disabled. Refer to CTRLA39.8.1 Control A for details.