Bounds on FSM Switching Activity

This paper obtains lower and upper bounds for the switching activity on the state lines of a finite state machine (FSM) that is driven by typical input sequences. More specifically, the paper provides bounds on the average Hamming distance which is in turn proportional to the switching activity and the overall power dissipation in the system. By introducing the concepts of a distance matrix and a weight matrix, and by exploiting the symmetry of the distance matrix, we are able to obtain bounds that are provably tighter than existing bounds and, as demonstrated by our experimental results, they can offer significant improvements in many cases of interest. Since our bounds are independent of the state assignment and the actual implementation, they can be used at an early stage of the FSM design to indicate the largest/smallest possible power consumption.