146
8331B–AVR–03/12
Atmel AVR XMEGA AU
13.3.1.2
Totem-pole with Pull-up
In this mode, the configuration is as for totem-pole, expect the pin is configured with internal pull-
up when set as input.
Figure 13-4.
I/O pin configuration - Totem-pole with pull-up (on input).
13.3.2
Bus-keeper
In the bus-keeper configuration, it provides a weak bus-keeper that will keep the pin at its logic
level when the pin is no longer driven to high or low. If the last level on the pin/bus was 1, the
bus-keeper configuration will use the internal pull resistor to keep the bus high. If the last logic
level on the pin/bus was 0, the bus-keeper will use the internal pull resistor to keep the bus low.
Figure 13-5.
I/O pin configuration - Totem-pole with bus-keeper.
13.3.3
Wired-OR
In the wired-OR configuration, the pin will be driven high when the corresponding bits in the OUT
and DIR registers are written to one. When the OUT register is set to zero, the pin is released,
allowing the pin to be pulled low with the internal or an external pull-resistor. If internal pull-down
is used, this is also active if the pin is set as input.
INn
OUTn
DIRn
Pn
INn
OUTn
DIRn
Pn