Quartus® Prime Pro Edition User Guide: Timing Analyzer

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ID 683243
Date 9/30/2024
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Document Table of Contents
Document Table of Contents x
Answers to Top FAQs 1. Timing Analysis Introduction 2. Using the Quartus® Prime Timing Analyzer A. Quartus® Prime Pro Edition User Guides
1. Timing Analysis Introduction x
1.1. What's New In This Version 1.2. Timing Analysis Basic Concepts 1.3. Timing Analysis Overview Document Revision History
1.2. Timing Analysis Basic Concepts x
1.2.1. Timing Path and Clock Analysis 1.2.2. Clock Setup Analysis 1.2.3. Clock Hold Analysis 1.2.4. Recovery and Removal Analysis 1.2.5. Multicycle Path Analysis 1.2.6. Metastability Analysis 1.2.7. Timing Pessimism 1.2.8. Clock-As-Data Analysis 1.2.9. Multicorner Timing Analysis 1.2.10. Time Borrowing
1.2.1. Timing Path and Clock Analysis x
1.2.1.1. The Timing Netlist 1.2.1.2. Timing Paths 1.2.1.3. Data and Clock Arrival Times 1.2.1.4. Launch and Latch Edges
1.2.5. Multicycle Path Analysis x
1.2.5.1. Multicycle Clock Hold 1.2.5.2. Multicycle Clock Setup
1.2.10. Time Borrowing x
1.2.10.1. Time Borrowing Limitations 1.2.10.2. Time Borrowing with Latches 1.2.10.3. Enabling Time Borrowing Optimization
2. Using the Quartus® Prime Timing Analyzer x
2.1. Using Timing Constraints throughout the Design Flow 2.2. Timing Analysis Flow 2.3. Applying Timing Constraints 2.4. Timing Constraint Descriptions 2.5. Timing Report Descriptions 2.6. Scripting Timing Analysis 2.7. Using the Quartus® Prime Timing Analyzer Document Revision History 2.8. Quartus® Prime Pro Edition User Guide: Timing Analyzer Archive
2.2. Timing Analysis Flow x
2.2.1. Step 1: Specify General Timing Analyzer Settings 2.2.2. Step 2: Specify Timing Constraints 2.2.3. Step 3: Run the Timing Analyzer 2.2.4. Step 4: Analyze Timing Reports
2.2.2. Step 2: Specify Timing Constraints x
2.2.2.1. Specifying SDC-on-RTL Timing Constraints 2.2.2.2. Specifying Conventional SDC Timing Constraints 2.2.2.3. Specifying Synthesis-Only SDC Timing Constraints
2.2.3. Step 3: Run the Timing Analyzer x
2.2.3.1. Running Post-Synthesis Early Timing Analysis 2.2.3.2. Running Post-Fit Timing Analysis
2.2.3.2. Running Post-Fit Timing Analysis x
2.2.3.2.1. Setting the Operating Conditions for Timing Analysis 2.2.3.2.2. Promoting Critical Warnings to Errors
2.2.4. Step 4: Analyze Timing Reports x
2.2.4.1. Cross-Probing with Design Assistant 2.2.4.2. Launching Design Assistant from Timing Analyzer 2.2.4.3. Locating Timing Paths in Other Tools 2.2.4.4. Correlating Constraints to the Timing Report
2.2.4.1. Cross-Probing with Design Assistant x
2.2.4.1.1. Cross-Probing from Design Assistant to Timing Analyzer
2.3. Applying Timing Constraints x
2.3.1. Recommended Initial Conventional SDC Constraints 2.3.2. Example Circuit and Conventional SDC File 2.3.3. SDC File Precedence 2.3.4. Iteratively Modifying Constraints 2.3.5. Applying Entity-Bound Timing Constraints 2.3.6. Constraining Design Partition Ports 2.3.7. Using Fitter Overconstraints
2.3.1. Recommended Initial Conventional SDC Constraints x
2.3.1.1. Create Clock (create_clock) 2.3.1.2. Derive PLL Clocks (derive_pll_clocks) 2.3.1.3. Derive Clock Uncertainty (derive_clock_uncertainty) 2.3.1.4. Set Clock Groups (set_clock_groups)
2.3.5. Applying Entity-Bound Timing Constraints x
2.3.5.1. Using Entity-Based SDC-on-RTL Constraints 2.3.5.2. Using Entity-Bound SDC Files
2.3.5.1. Using Entity-Based SDC-on-RTL Constraints x
2.3.5.1.1. Targeting Constraints to Module Inputs and Outputs 2.3.5.1.2. Entity Based SDC-on-RTL Constraint Scope 2.3.5.1.3. Automatic Scope Example for SDC-on-RTL 2.3.5.1.4. Manual Scope Example for SDC-on-RTL
2.3.5.2. Using Entity-Bound SDC Files x
2.3.5.2.1. Entity-Bound SDC Constraint Scope 2.3.5.2.2. Automatic Scope Entity-bound Constraint Example 2.3.5.2.3. Manual Scope Entity-bound Constraint Example 2.3.5.2.4. Exporting a Design Partition with Entity-bound Constraints 2.3.5.2.5. Importing a Design Partition with Entity-bound Constraints
2.3.6. Constraining Design Partition Ports x
2.3.6.1. Timing Analysis of Imported Compilation Results
2.4. Timing Constraint Descriptions x
2.4.1. Clock Constraints 2.4.2. I/O Constraints 2.4.3. Delay and Skew Constraints 2.4.4. Timing Exception Constraints 2.4.5. Delay Annotation
2.4.1. Clock Constraints x
2.4.1.1. Creating Base Clocks 2.4.1.2. Creating Virtual Clocks 2.4.1.3. Creating Generated Clocks (create_generated_clock) 2.4.1.4. Deriving PLL Clocks 2.4.1.5. Creating Clock Groups (set_clock_groups) 2.4.1.6. Accounting for Clock Effect Characteristics 2.4.1.7. Constraining CDC Paths
2.4.1.1. Creating Base Clocks x
2.4.1.1.1. Automatic Clock Detection and Constraint Creation
2.4.1.2. Creating Virtual Clocks x
2.4.1.2.1. Specifying I/O Interface Uncertainty 2.4.1.2.2. I/O Interface Clock Uncertainty Example
2.4.1.3. Creating Generated Clocks (create_generated_clock) x
2.4.1.3.1. Clock Divider Example (-divide_by) 2.4.1.3.2. Clock Multiplexer Example
2.4.1.5. Creating Clock Groups (set_clock_groups) x
2.4.1.5.1. Exclusive Clock Groups (-logically_exclusive or -physically_exclusive) 2.4.1.5.2. Asynchronous Clock Groups (-asynchronous) 2.4.1.5.3. set_clock_groups Constraint Tips
2.4.1.6. Accounting for Clock Effect Characteristics x
2.4.1.6.1. Set Clock Latency (set_clock_latency) 2.4.1.6.2. Clock Uncertainty
2.4.2. I/O Constraints x
2.4.2.1. Deprecation of the blackbox Argument 2.4.2.2. Input Constraints (set_input_delay) 2.4.2.3. Output Constraints (set_output_delay)
2.4.3. Delay and Skew Constraints x
2.4.3.1. Advanced I/O Timing and Board Trace Model Delay 2.4.3.2. Maximum Skew (set_max_skew) 2.4.3.3. Net Delay (set_net_delay) 2.4.3.4. Data Delay (set_data_delay)
2.4.4. Timing Exception Constraints x
2.4.4.1. Timing Exception Precedence 2.4.4.2. False Paths (set_false_path) 2.4.4.3. Minimum and Maximum Delays 2.4.4.4. Multicycle Paths 2.4.4.5. Multicycle Exception Examples 2.4.4.6. Creating Efficient Timing Exceptions
2.4.4.4. Multicycle Paths x
2.4.4.4.1. Common Multicycle Applications 2.4.4.4.2. Relaxing Setup with Multicycle (set_multicyle_path) 2.4.4.4.3. Accounting for a Phase Shift (-phase)
2.4.4.5. Multicycle Exception Examples x
2.4.4.5.1. Default Multicycle Analysis 2.4.4.5.2. End Multicycle Setup = 2 and End Multicycle Hold = 0 2.4.4.5.3. End Multicycle Setup = 2 and End Multicycle Hold = 1 2.4.4.5.4. Same Frequency Clocks with Destination Clock Offset 2.4.4.5.5. Destination Clock Frequency is a Multiple of the Source Clock Frequency 2.4.4.5.6. Destination Clock Frequency is a Multiple of the Source Clock Frequency with an Offset 2.4.4.5.7. Source Clock Frequency is a Multiple of the Destination Clock Frequency 2.4.4.5.8. Source Clock Frequency is a Multiple of the Destination Clock Frequency with an Offset
2.5. Timing Report Descriptions x
2.5.1. Report Fmax Summary 2.5.2. Report Timing 2.5.3. Report Timing By Source Files 2.5.4. Report Data Delay 2.5.5. Report Net Delay 2.5.6. Report Clocks and Clock Network 2.5.7. Report Clock Transfers 2.5.8. Report Metastability 2.5.9. Report CDC Viewer 2.5.10. Report Asynchronous CDC 2.5.11. Report Logic Depth 2.5.12. Report Neighbor Paths 2.5.13. Report Register Spread 2.5.14. Report Route Net of Interest 2.5.15. Report Retiming Restrictions 2.5.16. Report Register Statistics 2.5.17. Report Pipelining Information 2.5.18. Report Time Borrowing Data 2.5.19. Report Exceptions and Exceptions Reachability 2.5.20. Report Bottlenecks 2.5.21. Check Timing 2.5.22. Report SDC
2.5.13. Report Register Spread x
2.5.13.1. Registers with High Timing Path Endpoint Tension 2.5.13.2. Registers with High Immediate Fan-Out Tension
2.5.20. Report Bottlenecks x
2.5.20.1. Specifying Custom Bottleneck Criteria
2.6. Scripting Timing Analysis x
2.6.1. The quartus_sta Executable 2.6.2. The quartus_staw Executable 2.6.3. Collection Commands
2.6.3. Collection Commands x
2.6.3.1. Wildcard Characters 2.6.3.2. Adding and Removing Collection Items 2.6.3.3. Query of Collections 2.6.3.4. Using the get_pins Command
Answers to Top FAQs
1. Timing Analysis Introduction
2. Using the Quartus® Prime Timing Analyzer
A. Quartus® Prime Pro Edition User Guides

1.2.7. Timing Pessimism

Common clock path pessimism removal accounts for the minimum and maximum delay variation associated with common clock paths during static timing analysis by adding the difference between the maximum and minimum delay value of the common clock path to the appropriate slack equation.

Minimum and maximum delay variation can occur when timing analysis uses two different delay values for the same clock path. For example, in a simple setup analysis, the maximum clock path delay to the source register determines the data arrival time. The minimum clock path delay to the destination register determines the data required time. However, if the clock path to the source register and to the destination register share a common clock path, both the maximum delay and the minimum delay model the common clock path during timing analysis. The use of both the minimum delay and maximum delay results in an overly pessimistic analysis since two different delay values, the maximum and minimum delays, cannot be used to model the same clock path.

Figure 30. Typical Register to Register Path

Segment A is the common clock path between reg1 and reg2. The minimum delay is 5.0 ns; the maximum delay is 5.5 ns. The difference between the maximum and minimum delay value equals the common clock path pessimism removal value; in this case, the common clock path pessimism is 0.5 ns. The Timing Analyzer adds the common clock path pessimism removal value to the appropriate slack equation to determine overall slack. Therefore, if the setup slack for the register-to-register path in the example equals 0.7 ns without common clock path pessimism removal, the slack is 1.2 ns with common clock path pessimism removal.

You can also use common clock path pessimism removal to determine the minimum pulse width of a register. A clock signal must meet a register’s minimum pulse width requirement for recognition by the register. A minimum high time defines the minimum pulse width for a positive-edge triggered register. A minimum low time defines the minimum pulse width for a negative-edge triggered register.

Clock pulses that violate the minimum pulse width of a register prevent data from latching at the data pin of the register. To calculate the slack of the minimum pulse width, the Timing Analyzer subtracts the required minimum pulse width time from the actual minimum pulse width time. The Timing Analyzer determines the actual minimum pulse width time by the clock requirement you specify for the clock that feeds the clock port of the register. The Timing Analyzer determines the required minimum pulse width time by the maximum rise, minimum rise, maximum fall, and minimum fall times.

Figure 31. Required Minimum Pulse Width time for the High and Low Pulse

With common clock path pessimism, the minimum pulse width slack can increase by the smallest value of either the maximum rise time minus the minimum rise time, or the maximum fall time minus the minimum fall time. In the example, the slack value can increase by 0.2 ns, which is the smallest value between 0.3 ns (0.8 ns – 0.5 ns) and 0.2 ns (0.9 ns – 0.7 ns).

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