188.8.131.52.2. Identifying Circuits for Shannon’s Decomposition
Shannon's decomposition is a good solution for circuits in which you can rearrange many inputs to control the final select stage. Account for new logic depths when restructuring logic to use a subset of the inputs to control the select stage. Ideally, the logic depth to the select signal is similar to the logic depth to the selector inputs. Practically, there is a difference in the logic depths because of difficulty in perfectly balancing the number of inputs feeding each cloud of logic.
Shannon’s decomposition may also be a good solution for a circuit with only one or two signals in the cone of logic that are truly critical, and others are static, or with clearly lower priority.
Shannon’s decomposition can incur a significant area cost, especially if the function is complex. There are other optimization techniques that have a lower area cost, as described in this document.