ETDD-based synthesis of term-based FPGAs for incompletely specified Boolean functions

Complex terms are logic expressions which can be mapped directly to cell arrays of cellular architecture devices such as Atmel 6000 series FPGAs. This paper presents an approach to generation of complex terms for incompletely specified Boolean functions using ETDD (EXOR Ternary Decision Diagram)s. Basically the decompositions, Shannon, positive Davio and negative Davio, inherent in ETDDs are employed to generate complex terms. While traversing the ETDD can be done in a simple and efficient way for completely specified functions, the manipulation of ETDDs with don´t care terms becomes very complex because the three decompositions require different evaluations of the function. The changes made to the function due to don´t cares in each decomposition are analyzed and an approximation algorithm is presented with its applications to the synthesis of complex terms