18.6.3.4 I/O Lines Retention in HIBERNATE or BACKUP Mode

When entering HIBERNATE or BACKUP mode, the PORT is powered off but the pin configuration is retained. When the device exits the HIBERNATE or BACKUP mode, the I/O line configuration can either be released or stretched, based on the I/O Retention bit in the Control A register (CTRLA.IORET).

• If IORET=0 when exiting HIBERNATE or BACKUP mode, the I/O lines configuration is released and driven by the reset value of the PORT.
• If the IORET=1 when exiting HIBERNATE or BACKUP mode, 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 programmed the PORT.