Why does the Quartus II software report unconstrained paths when running quartus_sta with the --sdc option to perform timing analysis?

You may observe Quartus® II software report unconstrained paths while running quartus_sta with the --sdc option to perform timing analysis. This behavior may occur even though there are no unconstrained paths when running a full compilation. If you use the --sdc option for the quartus_sta command, the software uses only the constraints in the specified Synopsys Design Constraints (.sdc) file for timing analysis, but not the embedded timing constraints in your design files.

To avoid this behavior, do one of the following actions:

• Include the command read_sdc -hdl within your specified .sdc file to have the software use the embedded constraints.
• Remove the --sdc option. Without the --sdc option, the software performs timing analysis using the embedded constraints in design files and the .sdc files in your project.