interview 3 Flashcards
(19 cards)
How do you deal with design-side uncertainty?
I use a physics-first approach: I rely on physical principles, analyze behavior systematically, and speak the same technical language as design teams.
This approach ensures that the analysis is rooted in fundamental laws, providing a consistent framework for understanding design challenges.
Why are you suitable for a design-facing role?
Because I help design teams save time by exposing hidden risks early. I combine physical understanding with automation and practical tool development.
This combination enhances efficiency and reduces the likelihood of costly design errors.
What is the benefit of using a physics-first approach in design?
It provides a consistent framework based on unchanging physical principles.
This allows for systematic analysis and better communication with design teams.
What is a key advantage of exposing hidden risks early in the design process?
It saves time for design teams.
Early identification of risks can lead to more informed decision-making and reduced project delays.
Fill in the blank: Patterns and causes can be _______.
learned and traced.
Understanding patterns helps in predicting outcomes and improving design processes.
True or False: Physics principles change over time.
False.
Physics principles are constant and provide a reliable basis for analysis.
What does combining physical understanding with automation achieve?
It enhances practical tool development.
This integration streamlines processes and improves design accuracy.
why CDC or formal verification?
“While my direct experience with formal verification is limited, I understand that tools like JasperGold and VC Formal are used to mathematically prove CDC correctness. They exhaustively check for metastability, glitches, and data loss at clock domain boundaries—issues that traditional simulation often misses. This is especially critical in complex SoCs with multiple asynchronous domains, where CDC bugs are a leading cause of silicon re-spins.”
What is assertion-based verification?
It is a method where specific properties (assertions) are written into the code to automatically check that the design behaves as intended during simulation or formal verification.
Assertion-based verification enhances design reliability by ensuring critical properties are validated during the verification process.
What is a SystemVerilog assertion?
A SystemVerilog assertion is a statement that must always be true in the design. If it is violated, an error is reported.
SystemVerilog assertions are crucial for identifying design errors early in the development cycle.
What are the two main types of assertions in SystemVerilog?
- Immediate assertions
- Concurrent assertions
Immediate assertions are checked at a specific time, while concurrent assertions are checked over time, which is useful for temporal properties.
Why are assertions important for CDC (Clock Domain Crossing) verification?
CDC issues, such as metastability and data loss, are hard to catch with simulation alone. Assertions can formally prove that data crossing between clock domains is safe and correct.
CDC verification is critical for ensuring reliable operation in designs with multiple clock domains.
What is formal verification?
Formal verification uses mathematical methods and tools to exhaustively check that all possible behaviors of a design meet the specified assertions, rather than relying on testbenches or simulation.
This approach provides a higher level of assurance compared to traditional verification methods.
How do tools like JasperGold and VC Formal help with CDC analysis?
These tools automatically analyze the design and its assertions to prove that CDC paths are safe, checking for issues like metastability, data loss, and protocol violations using exhaustive, mathematical methods.
Utilizing formal verification tools can significantly reduce the time spent on debugging and increase confidence in design correctness.
What is an example of a simple assertion for a handshake protocol?
“If a request is made, an acknowledge must eventually follow.” In SVA:
text
property req_ack;
@(posedge clk) req |-> ##[1:$] ack;
endproperty
assert property (req_ack);
This assertion ensures that the protocol behaves correctly by requiring an acknowledgment to follow a request.
What is the benefit of using formal tools for CDC versus simulation?
Formal tools can exhaustively check all possible scenarios and timing relationships, catching bugs that simulation might miss due to limited coverage.
This exhaustive approach provides a more comprehensive verification process, especially for complex designs.
What should you do if you are not experienced with UVM or CDC tools?
Emphasize your understanding of the concepts, willingness to learn, and ability to collaborate with verification experts or quickly ramp up on these tools if needed.
Demonstrating a proactive attitude towards learning can be beneficial in a technical interview or job setting.
What is the typical workflow for assertion-based CDC verification?
- Identify signals crossing clock domains
- Write assertions describing correct behavior at these crossings
- Use formal tools (like JasperGold or VC Formal) to prove assertions hold in all cases
- Debug and refine assertions as needed
Following a structured workflow helps in systematically addressing CDC issues and improving design reliability.
