An Integrated Approach of Variable Ordering and Logic Mapping into LUT-Array-Based PLD

This paper presents an approach of logic mapping into LUT-Array-Based PLD where Boolean functions in the form of the sum of generalized complex terms (SGCTs) can be mapped directly. While previous mapping approach requires predetermined variable ordering, our approach performs mapping and variable reordering simultaneously. For the purpose, we propose a directed acyclic graph based on the multiplevalued decision diagram (MDD) and an algorithm to construct the graph. Our algorithm generates candidates of SGCT expressions for each node in a bottom-up manner and selects the variables in the current level by evaluating the sizes of SGCT expressions directly. Experimental results show that our approach reduces the number of terms maximum to 71 percent for the MCNC benchmark circuits. key words: reconfigurable system, design technology, logic synthesis, variable ordering, look-up table