Timing Analysis Using Functional Analysis

The usual block-oriented timing analysis for logic circuits does not take into account functional relations between signals. If functional relations are taken into consideration, it may be found that a long path is never activated. This results in more accurate delays. This paper compares three arrival time functions–A, B, and R. Each one of these arrival time functions provides a set of times when a given signal is valid. A is the arrival time as given by exhaustive simulation. B is the arrival time as calculated by a usual block-oriented algorithm. R is the arrival time introduced in this paper, which does functional analysis. This paper will show that B ⊑R ⊑ A. The first relation means that R is never more conservative thanB and whenever the containment is proper, R is an improvement over B. The second relation means that R is correct in the sense that it will never assert a signal to be valid when it is not valid according to the idea A. The paper includes experimental results showing how often R is an improvement over B. © 1988 IEEE