Sequential logic rectifications with approximate SPFDs

In the digital VLSI cycle, logic transformations are often required to modify the design to meet different synthesis and optimization goals. Logic transformations on sequential circuits are hard to perform due to the vast underlying solution space. This paper proposes an SPFD-based sequential logic transformation methodology to tackle the problem with no sacrifice on performance. It first presents an efficient approach to construct approximate SPFDs (aSPFDs) for sequential circuits. Then, it demonstrates an algorithm using aSPFDs to perform the desirable sequential logic transformations using both combinational and sequential don't cares. Experimental results show the effectiveness and robustness of the approach.