Reference Clock Input StructureFunctional DescriptionThe reference clock input structure is illustrated in Figure 2-1. The input is terminatedinternally with 50 on each leg to 4/5 MGTAVCC. The reference clock is instantiated insoftware with the IBUFDS_GTE2 software prim itive. The ports and attributes controllingthe reference clock input are tied to the IBUFDS_GTE2 software primitive.Figure 2-1 shows the internal structure of the reference clock input buffer.