The Bus Skew Report
Summary section reports all the set_bus_skew constraints defined in the design. The following information
is reported for each constraint:
- Id
- Constraint ID referred to later in the report. This information makes it easier to search for that constraint within the report.
- From
- Pattern provided for the
set_bus_skew -fromoption. - To
- Pattern provided for the
set_bus_skew -tooption. - Corner
- Corner (Slow or Fast) in which the worst bus skew was computed.
- Requirement
- Bus skew target value.
- Actual
- Worst bus skew computed across all the paths covered by the constraint.
- Slack
- Difference between the worst bus skew and the constraint requirement.
In the following example, the design has only one bus skew constraint with a 1 ns requirement. The worst skew among all the paths covered by the constraint is 1.107 ns.
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Note: A bus skew violation (WBSS)
indicates that there is more skew between the different bits of an asynchronous bus
than expected. This can result in incorrect data on the bus being captured in the
destination clock domain. In such cases, the different bits of the bus could reflect
a state sent by the source clock domain at different clock cycles. When one or more
WBSS violations are left after routing, try a different routing or placement
directive. For hardware stability, it is recommended to ensure that there is no bus
skew violation left in the design.