The clock skew between two different sequential components is the difference between the insertion delays from the clock source to the clock pins of these components. SmartTime calculates the arrival time at the clock pin of each sequential component. Then it subtracts the arrival time at the receiving component from the arrival time at the launching component to obtain an accurate clock skew.
Both setup and hold checks must account for clock skew. However, for setup check, SmartTime looks for the smallest skew. This skew is computed by using the maximum insertion delay to the launching sequential component and the shortest insertion delay to the receiving component.
For hold check, SmartTime looks for the largest skew. This skew is computed by using the shortest insertion delay to the launching sequential component and the largest insertion delay to the receiving component. SmartTime makes this distinction automatically.