Initialization

For basic operation, follow these steps:

Configure the desired input pin in the PORT peripheral as an analog pin with digital input buffer disabled. Internal pull-up and pull-down resistors must also be disabled.
Optional: Enable the output pin by writing a ‘1’ to the Output Enable (OUTEN) bit in the Control A (ZCDn.CTRLA) register.
Enable the ZCD by writing a ‘1’ to the ENABLE bit in ZCDn.CTRLA

After the ZCD is enabled, there is a start-up time during which the output of the ZCD may be invalid. The start-up time can be determined by referring to the ZCD electrical characteristics for the device.