The Clock Pair Classification column explains why the tool considers two clocks synchronous or asynchronous. The tool stops checking as soon as it detects one of the conditions below, listed in order of priority:
- Ignored
- A clock group, false path, or max delay datapath-only constraint
covers the entire clock pair.Note: When a clock pair is covered by a max delay datapath only, the Inter-Clock Constraints are reported as Max Delay Datapath Only during setup analysis and as Auto Generated False Path during hold analysis (
-delay_type min).
- Virtual Clock
- One or both clocks are virtual, so common primary clock or node checks do not apply
- No Common Clock
- The clocks do not share a common primary clock
- No Common Period
- The periods are not expandable
- Partial Common Node
- The two clocks appear synchronous, but a subset of the crossing paths does not have a common node and cannot be safely timed
- No Common Node
- The two clocks appear synchronous, but the crossing paths do not have a common node
- No Common Phase
- The clocks lack a known phase relationship
- Clean
- None of the above conditions apply.