Inputs: 

Crystal Inputs 

For applications not requiring the use of the crystal oscillator input,  both XTAL_IN and XTAL_OUT can be left floating. Though not  required, but for additional protection, a 1kΩ resistor can be tied from  XTAL_IN to ground.  

LVCMOS_CLK Input 

For applications not requiring the use of a clock input, it can be left  floating. Though not required, but for additional protection, a 1kΩ resistor can be tied from the LVCMOS_CLK to ground. 

LVCMOS Control Pin 

The control pin has an internal pulldown; additional resistance is not  required but can be added for additional protection. A 1kΩ resistor  can be used.

Outputs: 

LVCMOS Outputs 

All unused LVCMOS outputs can be left floating. We recommend that  there is no trace attached.