Crosstalk delay on timing verificaiton

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Figure 1  Crosstalk in data and clock paths

1.  Setup analysis

• Launch clock path sees positive crosstalk delay so that data is launched late.
• Data path sees positive crosstalk delay so that it takes longer for data to reach destination (D pin in capture FF).
• Capture clock path sees negative crosstalk delay so that data is captured by capture FF early.

Since launch and capture clock edges for a setup check are different (normally one clock cycle apart), common clock path can have different crosstalk contributions for launch and capture clock edges.

2.  Hold analysis

There is one important difference between hold and setup analyses related to crosstalk on common portion of clock path (launch and capture). Launch and capture clock edge are normally the same edge for hold analysis. Clock edge through common clock portion cannot have different crosstalk contributions for launch clock path and capture clock path. Therefore, the worst-case hold analysis removes crosstalk contribution from common clock path.
Setup analysis concerns two different edges of clock which may be impacted differently in time. Thus, common path crosstalk contributions are considered for both launch and capture paths during setup analysis.

• Launch clock (not including common path) sees negative crosstalk delay so that data is launched early.
• Data path sees negative cross talk delay so that it reaches destination early (D pin in capture FF).
• Capture clock (not including common path) sees positive crosstalk delay so that data is captured by capture FF late.

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