----- Port Pin Configurations -------
DDxn PORTxn PUD (in MCUCR) I/O Pull-up Comment
0 0 X Input Tri-state (Hi-Z)
0 1 0 Input <-- Pull-up aktiv
0 1 1 Input Tri-state (Hi-Z)
1 0 X Output Output Low (Sink)
1 1 X Output Output High (Source)