The inputs on the NXP PCAL6524 i/o expander can be configured with internal pull-up or pull-down resistors.
The datasheet states, "External resistors are required for inputs... that may float. If a driver to an input will never let the input float, a resistor is not needed with internal pull-up or pull-down resistor option."
I thought the whole point of a pull-up or pull-down resistor was to allow the input to float, so I don't understand what the datasheet is saying. Why would you need or want a pull-up or pull-down resistor if the input is not floating?