MMMC (Multi-Mode Multi-Corner)

Definition: Multi-Mode Multi-Corner (MMMC) is a comprehensive methodology used in static timing analysis (STA) to verify the timing performance of a digital circuit under various operating modes and environmental conditions. MMMC combines multiple functional modes (e.g., normal, sleep, test) with multiple process, voltage, and temperature (PVT) corners to ensure the circuit meets its timing requirements across all specified scenarios.

Key Points:

  • Verifies timing across multiple functional modes and PVT corners simultaneously
  • Ensures the circuit operates correctly under all specified conditions
  • Provides a comprehensive coverage of the design space
  • Enables the identification of mode-specific and corner-specific timing violations
  • Supports the optimization of the circuit for multiple scenarios

Functional Modes:

  • Different operating modes of the circuit, such as normal, sleep, test, etc.
  • Each mode may have different timing requirements and constraints
  • Modes are typically defined by the application and the system requirements
  • Examples: high-performance mode, low-power mode, scan test mode

PVT Corners:

  • Different combinations of process, voltage, and temperature (PVT) conditions
  • Represent the extremes of the operating environment and manufacturing variations
  • Typically includes best-case, worst-case, and typical corners
  • Examples: slow-slow (SS), fast-fast (FF), typical-typical (TT)

MMMC Flow:

  1. Define the functional modes and PVT corners for the design
  2. Characterize the cell libraries and interconnects for each mode and corner
  3. Create mode- and corner-specific timing constraints and scenarios
  4. Run STA for each combination of mode and corner
  5. Analyze the timing reports and identify violations
  6. Optimize the design to meet timing across all modes and corners

Benefits of MMMC:

  • Ensures the robustness and reliability of the circuit under various operating conditions
  • Identifies mode-specific and corner-specific timing violations
  • Enables the optimization of the circuit for multiple scenarios
  • Reduces the risk of timing failures and improves the overall yield
  • Provides a comprehensive verification of the design’s timing performance

Challenges:

  • Increased complexity and runtime due to the large number of mode and corner combinations
  • Managing and maintaining multiple sets of libraries, constraints, and scenarios
  • Balancing the trade-offs between different modes and corners during optimization
  • Ensuring the consistency and accuracy of the timing models across modes and corners

Best Practices:

  • Carefully define the functional modes and PVT corners based on the system requirements
  • Use a consistent naming convention for modes, corners, and scenarios
  • Leverage automation and scripting to manage the complexity of the MMMC flow
  • Regularly review and update the MMMC setup to reflect design changes and new requirements

MMMC is a crucial methodology in modern VLSI design to ensure the timing performance and reliability of digital circuits under various operating conditions. By verifying the design across multiple functional modes and PVT corners, MMMC provides a comprehensive coverage of the design space and helps to identify and resolve potential timing issues early in the design cycle.