Inferred Tristate buffers are implemented with different device primitives when driving the following:
•An external pin of the circuit (OBUFT)
•An Internal bus (BUFT):
°An inferred BUFT is converted automatically to logic realized in LUTs by Vivado synthesis.
°When an internal bus inferring a BUFT is driving an output of the top module, the Vivado synthesis infers an OBUF.