2.1. When to Use the Netlist Viewers: Analyzing Design Problems
You can use the Netlist Viewers to analyze and debug your design. The following simple examples show how to use the RTL Viewer, State Machine Viewer, and Technology Map Viewer to analyze problems encountered in the design process.
Using the RTL Viewer is a good way to view your initial synthesis results to determine whether you have created the necessary logic, and that the logic and connections have been interpreted correctly by the software. You can use the RTL Viewer and State Machine Viewer to check your design visually before simulation or other verification processes. Catching design errors at this early stage of the design process can save you valuable time.
If you see unexpected behavior during verification, use the RTL Viewer to trace through the netlist and ensure that the connections and logic in your design are as expected. You can also view state machine transitions and transition equations with the State Machine Viewer. Viewing your design helps you find and analyze the source of design problems. If your design looks correct in the RTL Viewer, you know to focus your analysis on later stages of the design process and investigate potential timing violations or issues in the verification flow itself.
You can use the Technology Map Viewer to look at the results at the end of Analysis and Synthesis. If you have compiled your design through the Fitter stage, you can view your post‑mapping netlist in the Technology Map Viewer (Post-Mapping) and your post‑fitting netlist in the Technology Map Viewer. If you perform only Analysis and Synthesis, both the Netlist Viewers display the same post‑mapping netlist.
In addition, you can use the RTL Viewer or Technology Map Viewer to locate the source of a particular signal, which can help you debug your design. Use the navigation techniques described in this chapter to search easily through your design. You can trace back from a point of interest to find the source of the signal and ensure the connections are as expected.
The Technology Map Viewer can help you locate post‑synthesis nodes in your netlist and make assignments when optimizing your design. This functionality is useful when making a multicycle clock timing assignment between two registers in your design. Start at an I/O port and trace forward or backward through the design and through levels of hierarchy to find nodes of interest, or locate a specific register by visually inspecting the schematic.
Throughout your FPGA design, debug, and optimization stages, you can use all of the netlist viewers in many ways to increase your productivity while analyzing a design.
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