Clock and Reset Handling in Emulation

In the verification of integrated circuits (ICs), clock and reset handling is a critical aspect that ensures the reliability and functionality of digital systems. Emulation offers a powerful platform for thoroughly verifying these signals before hardware fabrication. This blog delves into advanced techniques for clock and reset handling in emulation, with a focus on specific cases and practical applications.

Importance of Clock and Reset Handling​

Clock and reset signals are foundational to digital circuit operation. The clock synchronizes various components, while the reset initializes the system, ensuring it starts from a known state. Effective handling of these signals during emulation is crucial for identifying and correcting timing issues early in the design process.

Advanced Clock Handling Techniques​

1. Clock Domain Crossing (CDC) Verification
In modern ICs, multiple clock domains are common, making CDC verification essential to prevent metastability and data corruption.

Case Study:
A multi-core processor design utilized CDC verification tools like Blue Pearl Visual Verification. These tools allowed the design team to visualize and analyze clock domain interactions, identify potential CDC issues, and implement solutions, ensuring reliable data transfer across domains.

Implementation:
CDC verification involves adding synchronizers at clock domain boundaries and using formal verification tools to ensure proper signal transfer. By rigorously testing these boundaries, potential issues can be detected and corrected early, preventing functional failures in the final hardware.

2. Dynamic Frequency Scaling (DFS)
DFS allows clock frequency adjustments based on performance requirements, optimizing power consumption without compromising functionality.

Case Study:
An automotive electronics company implemented DFS in their ADAS systems. Emulation was crucial for verifying the correct implementation of DFS, ensuring that frequency transitions did not introduce timing errors and that the system performed reliably under various operating conditions.

Implementation:
DFS verification in emulation involves testing the system under various frequency scenarios. This ensures that the system remains stable and performs as expected regardless of the clock frequency. Emulation tools must support rapid frequency changes and accurately model their impact on system performance.

Advanced Reset Handling Techniques​

1. Asynchronous vs. Synchronous Resets
The choice between asynchronous and synchronous resets can significantly impact the reliability and complexity of reset logic. Asynchronous resets are independent of the clock signal, while synchronous resets are synchronized with the clock.

Case Study:
A SoC design team opted for asynchronous resets with synchronous deassertion. This hybrid approach allowed the system to initialize quickly upon power-up while ensuring reset deassertion did not violate timing constraints. Emulation validated this strategy under various conditions, proving its robustness and reliability.
Implementation:

• Asynchronous Reset Assertion: Used for immediate reset, independent of the clock.
• Synchronous Reset Deassertion: Ensures timing consistency when the reset signal is deactivated, preventing timing violations.
• Verification Strategy: Emulation tests both the assertion and deassertion phases, checking for proper initialization and timing adherence.

2. Reset Domain Crossing (RDC) Verification
RDC verification ensures that resets crossing different clock domains do not cause unpredictable behavior, which is crucial for system stability.

Case Study:
An FPGA design team employed Blue Pearl’s RDC analysis to verify their designs for radiation-hardened applications. Thorough RDC checking ensured reliable reset behavior, even in harsh environments, preventing unexpected issues during operation.
Implementation:

• Synchronization of Reset Signals: Ensuring that resets are synchronized when crossing domains to avoid glitches and metastability.
• RDC Analysis Tools: Using emulation tools to model and verify reset signal behavior across domains.

Practical Applications​

1. 5G Network Equipment
Robust clock and reset handling ensures reliable performance in 5G network equipment, which requires stringent timing and synchronization.
Case Study:
A telecom company used advanced emulation techniques to verify their 5G baseband processor. Emulation allowed them to simulate various network conditions and configurations, ensuring the processor handled high data rates and dynamic environments reliably.
Implementation:

• Network Condition Simulation: Emulation of different operational scenarios to verify clock and reset stability.
• Stress Testing: Ensuring the processor can handle extreme conditions without failure.

2. Automotive Electronics
In automotive systems, particularly those involving autonomous driving, robust clock and reset handling is critical for safety and reliability.
Case Study:
An automotive manufacturer employed emulation to validate the clock and reset logic of their autonomous driving platform. Emulation enabled them to test the system’s response to various reset conditions, ensuring critical safety features functioned correctly under all circumstances.
Implementation:

• Safety-Critical Testing: Ensuring that the system responds predictably to resets in all scenarios.
• Multi-Domain Verification: Verifying clock and reset handling across multiple domains to ensure overall system integrity.