Difference Between Launch and Capture Distances in an AOCV Analysis

In a path-based analysis, the distance of a path is the diagonal of the bounding box that encompasses all of the arcs in the path. In a graph-based analysis, an arc can be both launching and capturing. As a result, there are launch and capture distances. Maintaining separate launch and capture distances for arcs in a graph-based analysis vastly improves the accuracy of the results and allows closer correlation between the graph-based and path-based analyses.

The distinction between launch and capture distances can be best described using an example. In the schematic shown below, the BUF cell arc is treated as a capture arc. The cells that contribute to the bounding box for the BUFcell arc are highlighted in green. The launch and capture paths are shown with arrows. Note that the capture path passes through the BUF cell arc.

Figure 1: BUF Cell Arc Treated as a Capture Arc

In the schematic shown below, the BUF cell arc is treated as a launch arc. The cells that contribute to the bounding box for the BUF cell arc are highlighted in red. The launch and capture paths are shown with arrows. Note that thelaunch path passes through the BUF cell arc.

Figure 2: BUF Cell Arc Treated as a Launch Arc

You can examine the launch and capture AOCV distances and depths using the report_aocvm command. For example,

pt_shell> report_aocvm [get_timing_arcs -of U3]