timing paths

timing paths

In this figure, Each path starts at a data point, passes through some combinational logic, and ends at a data capture point:

* path 1 starts at an input port and ends at the data input of a sequential element.
* path 2 starts at the clock pin of a sequential element and ends at the data input of a sequential element.
* path 3 starts at the clock pin of  a sequential element and ends at an output port.
* path 4 starts at an input port and ends at an output port.

Notes:
Each path has a startpoint and an endpoint. The startpoint is a place in the design where data is launched by a clock edge. The data is propagated through combinational logic in the path and then captured at the end point by another clock edge.
The startpoint of a path is a clock pin of a sequential element, or possibly an input port of the design ( because the input data can be launched from some external source.) The endpoint of a path is a data input pin of a sequential element, or possibly an output port of the design ( because the output data can be captured by some external sink).