Automatic FSM Synthesis for Low-power Mixed Synchronous/Asynchronous Implementation

Power consumption in a synchronous FSM (Finite-State Machine) can be reduced by partitioning it into a number of coupled sub-FSMs where only the part that is involved in a state transition is clocked. Automatic synthesis of a partitioned FSM includes a partitioning algorithm and sub-FSM synthesis to an implementation architecture. In this paper, we first introduce an implementation architecture for partitioned FSMs that uses gated-clock technique for disabling idle parts of the circuits and asynchronous controllers for communication between the sub-FSMs. We then describe a new transformation procedure for the sub-FSM. The FSM synthesis flow has been automated in a prototype tool that accepts an FSM specification. The tool generates synthesizable RT-level VHDL code with identical cycle-to-cycle input/output behavior in accordance with the specification. An average power reduction of 45% has been obtained for a set standard FSM benchmarks.