Automated Logic Restructuring with aSPFDs

This chapter presents a comprehensive methodology to automate logic restructuring in combinational and sequential circuits. This technique algorithmically constructs the required transformation by utilizing a functional flexibility representation called Set of Pairs of Function to be Distinguished (SPFD). SPFDs can express more functional flexibility than the traditional don’t cares and have proved to provide additional degrees of flexibility during logic synthesis [21, 27]. Computing SPFDs may suffer from memory or runtime problems [16]. Therefore, a simulation-based approach to approximate SPFDs is presented to alleviate those issues. The result is called Approximate SPFDs (aSPFDs). aSPFDs approximate the information contained in SPFDs using the results of test vector simulation. With the use of aSPFDs as a guideline, the algorithm searches for the necessary nets to construct the required function. Experimental results indicate that the proposed methodology can successfully restructure locations where a previous approach that uses a dictionary model [1] as the underlying transformation template fails.

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