Inter-Wire Coupling Reduction Analysis of Bus-Invert Coding

Bus-invert (BI) coding is the first encoding method for reducing peak and average self-switching power on a bus. It can also reduce capacitive coupling between bus lines. Although it is no longer used as a stand-alone method, it is often used as a starting point for developing a more sophisticated method. Despite its wide use, researchers in the past often resorted to simulations or depended on their intuition to obtain the switching and coupling characteristics. We clearly need a simple but accurate way to carry out this task. We previously published results on BI coding analysis for switching activity reduction. In this paper we conduct a theoretical analysis of BI coding for coupling reduction for uncorrelated uniformly distributed data. Our findings include a set of closed-form formulas for computing the number of couplings per bus transfer for a nonpartitioned versus a partitioned bus. These formulas are simple and easily understandable. They can be readily used for calculating couplings by simply plugging one or two parameter values into them.