ISE
Analyzing Unconstrained Paths
You can analyze paths that were not covered by constraints. Unconstrained paths are organized into different categories depending on the type of path that is unconstrained. These categories are identified by the type of global constraint that would be used to constrain these paths, such as OFFSET IN, PERIOD, and OFFSET OUT.
Note For more information on global constraints, see the Constraints Guide (UG625).
Constraint Analysis
Begin unconstrained path analysis by identifying the unconstrained category. The following example shows an unconstrained PERIOD analysis.
  1. In the Report Navigation pane, select the constraint, as shown in the following figure.
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  2. In the Timing Object Table, review the unconstrained paths associated with the selected constraint.
    This table shows the worst case paths for the selected constraint by showing each path, including common timing details associated with the path, as shown in the following figure.
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  3. In the Timing Report pane, review the summary details for the constraint.
    These details include summary information about the constraint and the number of paths and endpoints covered by the constraint. You can use this information to verify that the constraint covered the expected number of paths and endpoints and to gain a high-level view of the performance of the constraint. The following figure shows an example of the summary information.
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Detailed Path Analysis
Timing Analyzer provides a detailed path analysis for the unconstrained path. This analysis contains all of the information used to determine the timing of a single path. To analyze a detailed path, do the following:
  1. In the Report Navigation pane, select a path, as shown in the following figure.
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  2. In the Timing Report pane, review the details for the selected path.
    The details for an unconstrained path contain different groups of information, which you can review as follows:
    1. Review the first group, which is a summary of the unconstrained path timing performance. The summary section includes source register and destination pad information, transmitting clock network description, clock and data delay information, and any clock uncertainties. Because the path is unconstrained, setup and hold slack cannot be calculated. The following figure shows an example of this section.
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    2. Review the details of the data paths, including a detailed description of all components and network delays for the unconstrained path. The following figure shows an example of this section.
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See Also

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