AN 584: Timing Closure Methodology for Advanced FPGA Designs

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ID 683145
Date 10/08/2021
Public
Document Table of Contents
Document Table of Contents x
1. AN 584: Timing Closure Methodology for Advanced FPGA Designs
1. AN 584: Timing Closure Methodology for Advanced FPGA Designs x
1.1. Plan Early for Timing Closure 1.2. Customize Settings Per Application 1.3. Change Fitter Placement Seeds 1.4. Planning for Timing Closure 1.5. Best Practices for Timing Closure 1.6. Resolving Common Timing Issues 1.7. Conclusion 1.8. Document Revision History for AN 584: Timing Closure Methodology for Advanced FPGA Designs
1.4. Planning for Timing Closure x
1.4.1. Timing Closure Planning at Specification Stage 1.4.2. Timing Closure Planning at Coding and Compilation Stage
1.4.1. Timing Closure Planning at Specification Stage x
1.4.1.1. Plan for the Target FPGA Device 1.4.1.2. Plan for On-Chip Debugging
1.4.2. Timing Closure Planning at Coding and Compilation Stage x
1.4.2.1. Plan for Design Hierarchy and Block Partitioning 1.4.2.2. Plan for Early Compilation of Design Blocks 1.4.2.3. Plan for Verification
1.5. Best Practices for Timing Closure x
1.5.1. Performance Planning General Guidelines 1.5.2. Follow Synchronous Design Practices 1.5.3. Follow Recommended Coding Styles 1.5.4. Constraining and Compiling Your Design
1.5.4. Constraining and Compiling Your Design x
1.5.4.1. Setting Location Constraints 1.5.4.2. Setting Proper Timing Constraints 1.5.4.3. Using Optimal Compiler Settings for Your Design
1.6. Resolving Common Timing Issues x
1.6.1. Excessive Logic Levels 1.6.2. Improper Timing Constraints 1.6.3. Handling High Fan-Out Registers 1.6.4. Metastability Issues 1.6.5. Reset Signal Related Issues 1.6.6. Small Margin Timing Constraint Failures 1.6.7. Long Compilation Times
1.6.2. Improper Timing Constraints x
1.6.2.1. Check Constraint Diagnostics
1.6.4. Metastability Issues x
1.6.4.1. Check CDC Design Assistant Rule Violations 1.6.4.2. Check CDC Report
1.6.5. Reset Signal Related Issues x
1.6.5.1. Recovery and Removal Issues
1. AN 584: Timing Closure Methodology for Advanced FPGA Designs

1.6. Resolving Common Timing Issues

When the Timing Analyzer reports failing paths, verify if the failing requirements are correct. By default, the Timing Analyzer handles all clock domains as related, and this can cause some invalid requirements. To correct this condition, group clocks in your design appropriately. Analyze the datapath to determine how you can reduce any critical path delays.

This section contains examples of commonly encountered timing issues and troubleshooting practices:

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