Browse Prior Art Database

Elimination of False Timing Paths

IP.com Disclosure Number: IPCOM000110312D
Original Publication Date: 1992-Nov-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 87K

Publishing Venue

IBM

Related People

Brand, D: AUTHOR [+2]

Abstract

This article describes a synthesis transformation technique to make the longest path of a circuit statically sensitizable. This helps us find exact timing of a circuit.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 59% of the total text.

Elimination of False Timing Paths

       This article describes a synthesis transformation
technique to make the longest path of a circuit statically
sensitizable.  This helps us find exact timing of a circuit.

      Timing estimation is an important component of design.  Usually
timing information of a circuit is generated by topological analysis
without taking functionality into account.  It has been noted earlier
(1) that if functionality is taken into account during this
estimation process, the resultant maximum delay could be lower.
However, an exact analysis, taking functionality into account,
usually involves an impractical amount of computation.  Thus, the
designer has to contend with inaccurate timing information.  The
proposed synthesis technique removes this ambiguity by construction,
such that the longest topological path also becomes the longest
functional path.  This is done at the cost of possibly increasing
area and fanout.  Therefore, the transformation is restricted to
situations where it does not increase delay and does not increase
area excessively.

      The basic idea is illustrated through an example. Consider the
circuit given in Figure 1.  All single faults in the above circuit
are detectable.  The path C-1-3-6 in the above circuit is not
statically sensitizable for input C=1 but sensitizable for C=0.  If
there was no fanout branch from this path, it would imply that C
stuck-at 0 is redundant; however, this is not the case,...