
135
XMEGA A [MANUAL]
8077I–AVR–11/2012
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.
Figure 13-6. Output configuration - Wired-OR with optional pull-down.
INn
OUTn
DIRn
Pn
INn
OUTn
DIRn
Pn
INn
OUTn
Pn