DLPS117B July 2018 – October 2020 DLPC6421
To avoid potentially damaging current caused by floating CMOS input-only pins, it is recommended that unused ASIC input pins be tied through a pull-up resistor to its associated power supply or a pull-down to ground. For DLPC6421 inputs with an internal pull-up or pull-down resistors, it is unnecessary to add an external pull-up/ pull down unless specifically recommended. Note that internal pull-up & pull-down resistors are weak and should not be expected to drive the external line.
Unused output-only pins can be left open. When possible, it is recommended that unused Bi-directional I/O pins be configured to their output state such that the pin can be left open. If this control is not available and the pins may become an input, then they should be pulled-up (or down) using an appropriate resistor