guides

Timing Closure Guide

David Wang

Principal FAE - High-Speed Design

2024-02-10

💡 FAE Insights

📋 Customer Cases

Communications Equipment Vendor

Telecommunications

Challenge

Struggling with timing closure on 200MHz design

Solution

Applied timing closure methodology from this guide

Customer Feedback

"The systematic approach to timing closure saved our project schedule."

Results

Achieved timing closure
Improved clock speed by 20%
Reduced compile time

Frequently Asked Questions

1. How do I create timing constraints?

Constraint creation: (1) Clocks - Define all clock sources with create_clock. (2) I/O - Specify input/output delays. (3) Exceptions - Mark false paths and multicycle paths. (4) Derived - Create generated clocks for PLLs. (5) Verify - Check constraint coverage. Complete constraints are essential for proper analysis.

💡 Decision Guide: Contact LiTong for constraint development assistance.

2. What are false paths?

False paths: (1) Definition - Paths that don't need timing analysis. (2) Examples - Reset lines, test logic, asynchronous crossings. (3) Benefits - Reduces compile time, focuses optimization. (4) Syntax - set_false_path in constraints. (5) Care - Don't overuse, verify paths are truly false. Proper false path definition improves results.

💡 Decision Guide: Contact LiTong for false path identification.

3. How do I fix setup violations?

Setup violation fixes: (1) Pipeline - Add registers to break long paths. (2) Optimize - Restructure logic for faster paths. (3) Placement - Guide placement of critical logic. (4) Speed - Use faster speed grade device. (5) Clock - Reduce clock frequency. Pipelining is most effective solution.

💡 Decision Guide: Contact LiTong for setup violation analysis.

4. How do I fix hold violations?

Hold violation fixes: (1) Insertion - Add delay elements. (2) Clock - Adjust clock skew. (3) Optimization - Prevent over-optimization. (4) Constraints - Verify hold constraints correct. Hold violations are usually tool issues, not design issues.

💡 Decision Guide: Contact LiTong for hold violation resolution.

5. What is clock domain crossing?

Clock domain crossing: (1) CDC - Signals crossing between clock domains. (2) Synchronizers - Use 2+ flip-flop synchronizers. (3) FIFO - Use asynchronous FIFOs for data. (4) Constraints - Set false paths for CDC. (5) Verification - Check with CDC tools. Proper CDC handling prevents metastability.

💡 Decision Guide: Contact LiTong for CDC design guidance.

#Timing #Constraints #SDC #Optimization