How should unused input and output pins be terminated?
Input pins should never be left open or floating. The system may false trigger from noise if the inputs are left floating. It is recommended that all unused input pins be tied to a valid logic level using a resistor. The advantage of using pull-up or pull-down resistors is that they ensure a defined logic levels when the bus is floating. Typical resistor values range from 1 k-ohm to 10 k-ohms. Outputs may be left floating.
