28.4.4.4 I/O Line State Retention in Hibernate

When entering Hibernate , PORTs are powered off but the pin configuration is retained. When the device exits the Hibernate , the I/O line configuration can either be released or stretched, based on the I/O Retention bit in the CTRLA register (CTRLA.IORET).

If IORET = 0 when exiting Hibernate , the I/O lines configuration is released and driven by the reset values of each PORT.

If the IORET = 1 when exiting Hibernate , the configuration of the I/O lines is retained until the IORET bit is written to 0. It allows the I/O lines to be retained until the application has reprogrammed each PORT.