126.96.36.199. Unused Pin Settings
For example, if you reserve all unused pins as outputs driving ground, you must ensure that you do not connect unused I/O pins to VCC pins on your PCB. Connecting unused I/O pins to VCC pins may result in contention that could lead to higher than expected current draw and possible device overstress.
The Reserve all unused pins list shows available unused pin state options for the target device. The default state for each pin is the recommended setting for each device family.
When you reserve a pin as output driving ground, the Fitter connects a ground signal to the output pin internally. You should connect the output pin to the ground plane on your PCB, although you are not required to do so. Connecting the output driving ground to the ground plane is known as creating a virtual ground pin, which helps to minimize simultaneous switching noise (SSN) and ground bounce effects.
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