The OPAMP is enabled by writing a '1' to the Enable bit in the Control A register (CTRLA.ENABLE). The OPAMP is disabled by writing a '0' to CTRLA.ENABLE.
Each OPAMP sub-module is enabled by writing a '1' to the Enable bit in the OPAMP Control x register (OPAMPCTRLx.ENABLE). Each OPAMP sub-module is disabled by writing a '0' to OPAMPCTRLx.ENABLE.
The OPAMP module is reset by writing a '1' to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the OPAMP will be reset to their initial state, and the OPAMP will be disabled. Refer to CTRLA for details.