2.5.1 Physical Implementation

Implementing differential I/O standards requires the configuration of a pair of external I/O pads, resulting in a single internal signal. To facilitate construction of the differential pair, a single I/O Cluster contains the resources for a pair of I/Os. Configuration of the I/O Cluster as a differential pair is handled by Designer software when the user instantiates a differential I/O macro in the design.

Differential I/Os can also be used in conjunction with the embedded Input Register (InReg), Output Register (OutReg), Enable Register (EnReg), and Double Data Rate (DDR). However, there is no support for bidirectional I/Os or tristates with these standards.