It is shown that hazards can be optimally eliminated from circuits synthesized starting with a signal transition graph (STG) specification. The proposed approach is based on a linear programming (or integer linear programming) formulation, and as such it can be solved efficiently and optimally for a variety of cost functions. Suggested cost functions optimize either the total padded delay, an estimate of the increase in area, or the maximum cycle time of the complete system. It is also shown that delay padding on all fanouts of STG signals is a necessary and sufficient condition for hazard elimination if the structure and delay of each combinational logic block cannot be changed. Experimental results indicate that the improvements obtained are well worth the added complexity of linear program solution.
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