2.2.3 Unused I/O Pins

In case of Low-power modes, do not allow the unused I/O pins to float as inputs. They can be configured as outputs and driven to a Logic-low state. Alternatively, reserve the inputs by connecting the pin to VSS through a 1-10k resistor and configuring the pin as an input.

In general, the I/O pins need to be driven based on the application use-case. The user must know how a particular pin is wired before driving it to a particular state. For example, do not drive a pin to low if it is wired to sink current or drive high if it is going to source current.