13.3.2.1.1 Power-On Reset (POR)
A Power-on Reset (POR) is generated by an on-chip detection circuit. The POR is activated when the VDD rises until it reaches the POR threshold voltage. The POR is always enabled and will also detect when the VDD falls below the threshold voltage.
All volatile logic is reset on POR. All fuses are reloaded after the Reset is released.