The present invention provides a method for estimating the average-case
activity in a digital circuit. The method includes the steps of assigning
initial activity values to outputs of flops in the digital circuit, and
repeatedly updating the activity values in an iterative procedure until a
predetermined termination criterion is met. The updating of the activity
values uses a combination of standard probability updating techniques and
predetermined formulae for obtaining the activity values of predesignated
types of circuit elements in the digital circuit. The predesignated types
of circuit elements include, for example, one or more of a clock-gated
flop, an enable flop and a flop with a recirculation multiplexer.