|Specify the reserved state for unused I/O pins.
|Carefully check the pin connections in the Intel® Quartus® Prime software-generated .pin file. Do not connect RESERVED pins.
You can specify the state of unused pins in the Intel® Quartus® Prime software to allow flexibility in the board design by choosing one of the five allowable states for Reserve all unused pins on the Unused Pins category in the Device and Pin Options dialog box:
- As inputs tri-stated
- As output driving ground
- As outputs driving an unspecified signal
- As input tri-stated with bus-hold circuitry
- As input tri-stated with weak pull-up
The common setting is to set unused pins As inputs tri-stated with weak pull-up. To improve signal integrity, set the unused pins to As output driving ground. Doing this reduces inductance by creating a shorter return path and reduces noise on the neighboring I/Os. This approach should not be used if this results in many via paths causing congestion for signals under the device.
To reduce power dissipation, set clock pins and other unused I/O pins As inputs tri-stated, and tie them to ground.