A composition technique of multiple switching functions based on BDD

Binary Decision Diagram has a great impact on the Boolean function manipulation for its compressed and canonical presentation. In switching function organization ROBDD (Reduced Ordered Binary Decision Diagram) with a fixed variable ordering plays a significant role for its distinctiveness. Combination of multiple functions using switching operations has more redundant states. For removing these redundant states we apply ROBDD in this joining process. In this paper, we presented the way of combining n number of functions using ROBDD with a fixed variable ordering. In our proposed method at first, we compute each function's ROBDD over Shannon's expression. Then switching operations are going to be performed over these functions and ROBDD of the combinations of these functions are also computed. By this method, appearance of redundant states will be less. To construct an understandable and simple method, some examples have been used.