&gt; <i>You can&#x27;t build routing.</i><p>You actually don&#x27;t need configurable (programmable) routing: We can model every synchronous circuit as a Mealy machine [1], therefore we need two functions and a register. Every function can be constructed from a hierarchy of programmable, fixed-size LUTs which are statically connected (for example, you can build a 5-input LUT from three 4-input LUTs). Now you don&#x27;t need to build routing, it&#x27;s implicit in the next-state and output functions.<p>[1] like this: <a href="http:&#x2F;&#x2F;electrosofts.com&#x2F;verilog&#x2F;mealy.gif" rel="nofollow">http:&#x2F;&#x2F;electrosofts.com&#x2F;verilog&#x2F;mealy.gif</a>