To help you identify congestion, the Report Design Analysis command allows you to generate a congestion report that shows the congested areas of the device and the name of design modules present in these areas. The congestion tables in the report show the congested area seen by the placer and router algorithms. The following figure shows an example of the congestion table.
The Placed Maximum, Initial Estimated Router Congestion, and Router Maximum congestion tables provide information on the most congested areas in the North, South, East, and West direction. When you select a window in the table, the corresponding congested area is highlighted in the Device window.
The tables show the congestion at different stages of the design flow:
- Placed Maximum
- Shows congestion based on the location of the cells and a model of routing.
- Initial Estimated Router Congestion
- Shows congestion after a quick router iteration. This is the most useful stage to analyze congestion because it gives an accurate picture of congestion due to placement.
- Router Maximum
- Shows congestion after the router has worked extensively to reduce congestion.
The Congestion percentages in the Congestion Table show the routing utilization in the congestion window. The top three hierarchical cells located in the congested window are listed and can be selected and cross-probed to the Device window or Schematic window. The cell utilization percentage in the congestion window is also shown.
With the hierarchical cells present in the congested area identified, you can use the congestion alleviating techniques discussed later in this guide to try reducing the overall design congestion.
For more information on generating and analyzing the Report Design Analysis Congestion report, see this link in the Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906).