The following figure shows a simplified example of a CDC structure that includes
combinatorial logic. In this topology, a logic function implemented by a
LUT3 sits between the synchronizers from the clk_a
domain to the clk_b domain.
Figure 1. Combinatorial Logic Simplified Example
This structure is not recommended because glitches can occur at the output of the combinatorial logic. These glitches can be captured by the synchronizer and then propagate through the design, potentially causing unexpected behavior.