User`s guide

Methodolo

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For example, in the case of a convergence or reconvergence

hazard, look for conflicting rise/fall inputs. In the case of

cumulative ambiguity, look for the merging of successive

ambiguity regions within two edges forming a pulse.

Once the appropriate paths are identified, the relative timing of

the paths can be understood, and one of the following courses of

action may be taken:

• Modifying the stimulus (in the case of a simple convergence

hazard) to rearrange the relative timing of the signals

involved.

• Changing one or both of the path delays to accomplish the

same thing, by adding or removing logic, or by substitution

of component types with ones having different delay

characteristics.

Note that the first option is not generally effective in the case of

the reconvergent hazard since the difficulty lies between the

source of the reconvergent fanout and the location of the hazard.

The simulator has already determined that discounting the

common ambiguity did not preclude the hazard.

In the case of the cumulative ambiguity hazard, the most likely

solution will involve shortening the (one) path involved. This

may be done by:

• Adding a synchronization point to the logic, such as a flip-

flop, or perhaps simply gating the questionable signal with

a clock (having well-controlled ambiguity) before its

ambiguity can grow to unmanageable duration.

• Substituting faster components in the path, so that the

buildup of ambiguity happens less quickly.