FSM decomposition by direct circuit manipulation applied to low power design

Abstract

Clock-gating techniques are very effective in the reduction of the switching activity in sequential logic circuits. In particular, recent work has shown that significant power reductions are possible with techniques based on finite state machine (FSM) decomposition. A serious limitation of previously proposed techniques is that they require the state transition graph (STG) of the FSM to be given or extracted from the circuit. Since the size of the STG can be exponential on the number of registers in the circuit, explicit techniques can only be applied to relatively small sequential circuits. In this paper, we present a new approach to perform FSM decomposition by direct manipulation of the circuit. This way, we do not require the STG, either explicit or implicit, thus further avoiding the limitations imposed by the use of BDDs. Therefore, this technique can be applied to circuits with very large STGs. We provide a set of experimental results that show that power consumption can be substantially reduced, in some cases by more than 70%.