On the generation of multiplexer circuits for pass transistor logic

Pass Transistor Logic (PTL) has attracted more and more interest during recent years, since it has proved to be an attractive alternative to static CMOS designs with respect to area, performance and power consumption. Existing automatic PTL synthesis tools use a direct mapping of (decomposed) BDDs to pass transistors. Thereby, structural properties of BDDs like the ordering restriction and the fact that the select signals of the multiplexers (corresponding to BDD nodes) directly depend on input variables, are imposed on PTL circuits although they are not necessary for PTL synthesis. General multiplexer circuits can be used instead and should provide a much higher potential for optimization compared to a pure BDD approach. Nevertheless-to the best of our knowledge-an optimization of general Multiplexer Circuits (MCs) for PTL synthesis has not been tried so far due to a lack of suitable optimization approaches. In this paper we present such an algorithm which is based on efficient BDD optimization techniques. Our experiments prove that there is indeed a high optimization potential by the use of general MCs-both concerning area and depth of the resulting PTL networks.