Don't Cares in Synthesis: Theoretical Pitfalls and Practical Solutions

Effective use of don't cares requires solving several theoretical and practical problems. The theoretical problems are caused by a need to have all tools in a methology use a consistent semantics of don't cares, so as to guarantee correctness of the final implementation. Several common meanings of don't care will be considered and their respective conditions for design correctness will be derived. Several practical problems involving one kind of don't care, where design correctness can be guaranteed, will be discussed. These practical issues include: specifying don't cares in a language description, deriving them during high-level synthesis, and optimizing logic in their presence. Experimental results showing the impact of don't cares on logic quality are presented.

By: D. Brand, R.A. Bergamaschi and L. Stok

Published in: RC20127 in 1995


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