oClock groups might be updated after CTS based on new tree topologies causing new violation.
- Physical Detours and Congestion: The newly inserted clock buffers and routing can create congestion, forcing data path signals to take longer routes (detours) around the clock tree structures, thereby increasing their delay.
- CTS might trigger ECO fixes or buffer legalization that shifts data path buffers or cells.
- Actual skew values achieved is more than expected and considered in uncertainty, causing mismatch.
- CTS fixes DRC. And move around cells can cause timing violation.
- Very tight CTS constraint can cause CTS to add more buf/inv creating congestion and shifting nonCTS cells.