Accurate calculation of bit-level transition activity using word-level statistics and entropy function

Abstract

Accurate models for the calculation of bit level switching activity in data path operators, by combining the dual bit type model with the entropy based calculation are presented. Given the input statistics, the conditional entropy per bit is estimated by means of a sigmoidal model. A polynomial approximation to the entropy of the sign bits has been developed. Entropy and switching activity of primary inputs are used to estimate the output activity. The Triple-Bit Type (TBT) model is introduced to describe the behavior of the LSBs of the multiplier output, which do not behave as white noise. The error between the results of the proposed models and the measurements of entropy and switching activity is about 1% for signals with correlation factor less than 0.8.