29.6.1.1 Initialization

The EIC must be initialized in the following order:

1. Enable CLK EICAPB.
2. If required, configure the NMI by writing the Non-Maskable Interrupt Control (NMICTRL) register.
3. Enable GCLK EIC or CLK ULP32K when one of the following external interrupt, EIC_EXTINTx pins, modes is selected:
   • EIC_EXTINT pin filtering
   • EIC_EXTINT pin synchronous edge detection
   • EIC_EXTINT pin de-bouncing
   • GCLK EIC is used when a frequency higher than 32 kHz is required for filtering
   • CLK ULP32K is recommended when power consumption is the priority
4. For CLK ULP32K write a '1' to the Clock Selection bit in the Control A register (CTRLA.CKSEL).
5. Configure the EIC input sense and filtering by writing the Configuration n register (CONFIG).
6. Optionally, enable the Asynchronous mode.
7. Optionally, enable the Debounce mode.
8. Enable the EIC by writing a '1' to CTRLA.ENABLE.