What are the best practices for verifying cdc constraints in sta using formal methods?

1 Why formal methods?

Formal methods are mathematical techniques that can prove the correctness and consistency of a design or a specification. Unlike simulation or emulation, which rely on test cases and scenarios, formal methods can exhaustively explore all the possible states and behaviors of a design. Formal methods can also handle complex scenarios and corner cases that are hard to simulate or emulate. Formal methods are especially useful for verifying CDC constraints, because they can check the validity of the constraints, identify the sources and sinks of the CDC paths, and detect any potential glitches or hazards.

2 How to use formal methods?

Formal methods can be integrated into your STA flow as a complementary step, after you have defined your CDC constraints and before you run your STA tool. There are different types of formal methods that can be applied to verify CDC constraints, such as property checking, equivalence checking, or model checking. Depending on the tool and the method you choose, you may need to write some assertions or properties to specify the expected behavior and requirements of your CDC paths, or you may use some predefined templates or libraries provided by the tool. You may also need to set some parameters or options to control the scope and depth of the formal analysis.

3 What to check for?

When formally verifying CDC constraints in STA, you should check for completeness, consistency, correctness, and robustness. You should make sure that all the CDC paths are covered by your constraints, that they are consistent with your design intent and specifications, that they accurately reflect the timing behavior and requirements of your CDC paths, and that they are robust enough to handle any variations or uncertainties in your design or environment. Additionally, you need to ensure that your constraints prevent any glitches or hazards from propagating through your CDC paths.

4 What to do next?

After you run your formal methods tool, you should review the results and reports generated by the tool. You should look for any errors, warnings, or violations that indicate a problem with your CDC constraints or your design logic. You should also look for any recommendations or suggestions that can help you improve your CDC constraints or your design quality. You should fix any issues or errors that you find, and update your CDC constraints accordingly. You should also rerun your formal methods tool to confirm that your CDC constraints are verified and validated.

5 How to benefit from formal methods?

Using formal methods to verify CDC constraints in STA can bring you many advantages, such as saving time and resources by catching and fixing any CDC issues early on in the design cycle. This can prevent costly rework or redesign later on. Additionally, formal methods can provide a high level of assurance that your CDC constraints are correct and consistent, and that your design meets your specifications. Furthermore, you can benefit from the best practices and expertise of the formal methods tool vendors and the formal methods community, learning from their examples, templates, and libraries.