Method and system for determining a signal that controls the application of operands to a circuit-implemented function for power savings

摘要

A computer-implemented process for determining a signal function for use in controlling the application of signal operands to a circuit-implemented function for the purpose of power reduction. The present invention receives a netlist represented as a graph data structure having nodes interconnected with signal lines. A node can have one output (single fan-out) or can have more than one output (multiple fan-outs). Termination points of the graph are identified as inputs to registers or primary outputs. From the termination points, and using a breadth-first traversal process, the present invention traverses each node of the netlist. A parent node is not processed in the breadth-first traversal until all of its child nodes have been processed. During traversal, an activation signal function is constructed for each input of a node. If the node has multiple outputs then a disjunctive Boolean expression is used, otherwise a conjunctive Boolean expression is used to determine the activation signal function. Activation signal circuitry is then added to each node if the power savings meet certain specified area and timing considerations. Selected nodes have operand isolation circuitry added thereto to implement the activation signal functions. The activation signal circuitry is used to gate the operand signal inputs to the node thereby saving power when the node's output is ignored.