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AR# 55833

How to connect unused GT I/Os


Why does the documentation suggests to leave the unused GT I/O ports connected to GND, even though Xilinx development boards have all available GT I/Os floating?


The user guide (UG476) provides all of the required details about how to connect unused GT I/Os.

A floating I/O is needed on development boards because any GT I/O must be accessible for tests and measurements.

If a particular GT is not used, this does conflict with the user guide recommendation.

The user guide also suggests to ground unused GT I/Os because this is good design practice. 

However, an I/O that is floating or (that is a similar condition) connected to a decoupling capacitor will not break just because it is floating.

AR# 55833
Date 08/25/2017
Status Active
Type General Article
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