Method and apparatus for organizing and analyzing timing information
AssigneeDigital Equipment Corporation
InventorSteven K. Sherman
Life of this patent
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Abstract
A method and apparatus for analyzing signal timing requirements in complex electronic systems. The invention accepts from the user a set of specifications that express timing constraints, and generates therefrom a set of self-consistent "dependences" that relate signal locations to one another in terms of the minimum or maximum time that must elapse between such locations. The invention also generates signal pattern information that establishes the states of the various signals involved at different relevant times, and can be used to produce a signal profile.
Claims7
A method for generating signal pattern and dependence information from a plurality of timing specifications, each specification including a classification, a reference to at least one source signal and at least one destination signal, a time interval having magnitude and direction and a comparison expression, the method comprising the steps of:
- a. analyzing the specifications the determine whether:
- i. any timing inconsistencies exist among the specifications, and if so, recording the identity of each specification with respect to which an inconsistency exists;
- ii. if the specifications designate any clock signals, a valid period for each such clock signal is set forth, and if not, generating at least one additional specification to set forth such a valid period;
- iii. if the specifications designate any clock signals, a valid pulse width for each such clock signal is set forth, and if not, generating at least one additional specification to set forth such a valid pulse width;
- b. generating dependences from the specifications, each dependence including a type designation, a permissible timing interval, designation of at least one location on at least one signal, and a priority attribute;
- c. resolving inconsistencies among dependences generated from specifications identified as inconsistent by lowering the priority attribute of at least one dependence;
- d. generating at least one preliminary signal pattern that specifies a sequence of non-transition states separated by state boundaries, and which are consistent with the dependences, the state boundaries corresponding to signal locations of the dependences;
- e. replacing at least some of the state boundaries with transition states, each transition state including a permissible time interval and two transitions, to produce at least one final signal pattern;
- and
- f. replacing each dependence signal location with a designation of a transition.
Apparatus for generating signal pattern and dependence information from a plurality of timing specification, each specification including a classification, a reference to at least one signal, a time interval having magnitude and direction and a comparison expression, the apparatus comprising:
- a. first memory means for storing a plurality of specifications;
- b. second memory means, accessible by a user, for storing signal and pattern information;
- and
- c. processor means for
- i. analyzing the specifications to determine whether:
- (A) any timing inconsistencies exist among the specifications, and if so, recording the identity of each specification with respect to which an inconsistency exists;
- (B) if the specifications designate any clock signals, a valid period for each such clock signal is set forth, and if not, generating at least one additional specification to set forth such a valid period;
- (C) if the specifications designate any clock signals, a valid pulse width for each such clock signal is set forth, and if not, generating at least one additional specifications to set forth such a valid pulse width;
- ii. generating dependences from the specifications and storing the dependences in the second memory means, each dependence including a type designation, a permissible timing interval, designation of at least one location on at least one signal, and a priority attribute;
- iii. resolving inconsistencies among dependences generated from specifications identified as inconsistent by lowering the priority attribute of at least one dependence;
- and
- iv. generating at least one signal pattern and storing the at least one signal pattern in the second memory means, each signal pattern comprising a sequence of transition states and non-transition states that are consistent with the dependences.
Dependencies are inferred from the claim text.