STATE ENCODING OF FINITE-STATE MACHINES FOR LOW-POWER DESIGN

We address the problem of state encoding for synchronous finite state machines (FSMs), targeted for low power design. Most previous work in FSM state encoding has been focused on minimizing chip area and does n ot consider switching activity of the circuit. As a result, this does not always lead to a power efficient implementation. Especially in CMO S circuits, the switching activity is a very important factor to power dissipation. In this work, we define a function lambda for automatic tradeoff between switching activity and area that contribute to power dissipation. lambda is used in determining the encoding affinity betwe en states and is observed to be related to the number of states of an FSM in our experiments. A state encoding algorithm, based on hypercube embedding, is proposed to find encodings of states such that the sum of bit toggles between each pair of states times the encoding affinity between them is minimized. The proposed approach does not require any change in the functional specification of the state machine and can b e easily incorporated in present design flow. Results over a wide rang e of MCNC benchmark examples which show the efficacy of our technique are presented. A simple function for lambda is provided, and it is sho wn to be robust in finding low-power state encodings.