To avoid potentially damaging current caused by floating CMOS input-only pins, TI recommends tying unused controller input pins through a pullup resistor to its associated power supply or a pulldown resistor to ground. For controller inputs with internal pullup or pulldown resistors, it is unnecessary to add an external pullup or pulldown unless specifically recommended. Note that internal pullup and pulldown resistors are weak and should not be expected to drive an external device. The DLPC34xx controller implements very few internal resistors and are listed in the tables found in the Pin Configuration and Functions section. When external pullup or pulldown resistors are needed for pins that have weak pullup or pulldown resistors, choose a maximum resistance of 8 kΩ.

Never tie unused output-only pins directly to power or ground. Leave them open.

When possible, TI recommends that unused bidirectional I/O pins are configured to their output state such that the pin can remain open. If this control is not available and the pins may become an input, then include an appropriate pullup (or pulldown) resistor.