17.3.1 Initialization
After Reset, all standard function device I/O pads are connected to the port with outputs tri-stated and input buffers enabled, even if there is no clock running.
Power consumption can be reduced by disabling digital input buffers for all unused pins and for pins used as analog inputs or outputs.
Specific pins, such as those used for connecting a debugger, may be configured differently, as required by their special function.