Intel® Quartus® Prime Pro Edition User Guide: Timing Analyzer

Download PDF
ID 683243
Date 10/02/2023
Public

A newer version of this document is available. Customers should click here to go to the newest version.

Document Table of Contents
Document Table of Contents x
1. Answers to Top FAQs 2. Timing Analysis Introduction 3. Using the Intel® Quartus® Prime Timing Analyzer A. Intel® Quartus® Prime Pro Edition User Guides
2. Timing Analysis Introduction x
2.1. What's New In This Version 2.2. Timing Analysis Basic Concepts 2.3. Timing Analysis Overview Document Revision History
2.2. Timing Analysis Basic Concepts x
2.2.1. Timing Path and Clock Analysis 2.2.2. Clock Setup Analysis 2.2.3. Clock Hold Analysis 2.2.4. Recovery and Removal Analysis 2.2.5. Multicycle Path Analysis 2.2.6. Metastability Analysis 2.2.7. Timing Pessimism 2.2.8. Clock-As-Data Analysis 2.2.9. Multicorner Timing Analysis 2.2.10. Time Borrowing
2.2.1. Timing Path and Clock Analysis x
2.2.1.1. The Timing Netlist 2.2.1.2. Timing Paths 2.2.1.3. Data and Clock Arrival Times 2.2.1.4. Launch and Latch Edges
2.2.5. Multicycle Path Analysis x
2.2.5.1. Multicycle Clock Hold 2.2.5.2. Multicycle Clock Setup
2.2.10. Time Borrowing x
2.2.10.1. Time Borrowing Limitations 2.2.10.2. Time Borrowing with Latches
3. Using the Intel® Quartus® Prime Timing Analyzer x
3.1. Timing Analysis Flow 3.2. Step 1: Specify Timing Analyzer Settings 3.3. Step 2: Specify Timing Constraints 3.4. Step 3: Run the Timing Analyzer 3.5. Step 4: Analyze Timing Reports 3.6. Applying Timing Constraints 3.7. Timing Analyzer Tcl Commands 3.8. Timing Analysis of Imported Compilation Results 3.9. Using the Intel® Quartus® Prime Timing Analyzer Document Revision History 3.10. Intel® Quartus® Prime Pro Edition User Guide: Timing Analyzer Archive
3.4. Step 3: Run the Timing Analyzer x
3.4.1. Setting the Operating Conditions for Timing Analysis 3.4.2. Enabling Time Borrowing Optimization 3.4.3. Promoting Critical Warnings to Errors
3.5. Step 4: Analyze Timing Reports x
3.5.1. Generating Timing Reports 3.5.2. Cross-Probing with Design Assistant 3.5.3. Launching Design Assistant from Timing Analyzer 3.5.4. Locating Timing Paths in Other Tools 3.5.5. Correlating Constraints to the Timing Report
3.5.1. Generating Timing Reports x
3.5.1.1. Report Fmax Summary 3.5.1.2. Report Timing 3.5.1.3. Report Timing By Source Files 3.5.1.4. Report Data Delay 3.5.1.5. Report Net Delay 3.5.1.6. Report Clocks and Clock Network 3.5.1.7. Report Clock Transfers 3.5.1.8. Report Metastability 3.5.1.9. Report CDC Viewer 3.5.1.10. Report Asynchronous CDC 3.5.1.11. Report Logic Depth 3.5.1.12. Report Neighbor Paths 3.5.1.13. Report Register Spread 3.5.1.14. Report Route Net of Interest 3.5.1.15. Report Retiming Restrictions 3.5.1.16. Report Register Statistics 3.5.1.17. Report Pipelining Information 3.5.1.18. Report Time Borrowing Data 3.5.1.19. Report Exceptions and Exceptions Reachability 3.5.1.20. Report Bottlenecks
3.5.1.13. Report Register Spread x
3.5.1.13.1. Registers with High Timing Path Endpoint Tension 3.5.1.13.2. Registers with High Immediate Fan-Out Tension
3.5.1.20. Report Bottlenecks x
3.5.1.20.1. Specifying Custom Bottleneck Criteria
3.5.2. Cross-Probing with Design Assistant x
3.5.2.1. Cross-Probing from Design Assistant to Timing Analyzer
3.6. Applying Timing Constraints x
3.6.1. Recommended Initial SDC Constraints 3.6.2. SDC File Precedence 3.6.3. Modifying Iterative Constraints 3.6.4. Using Entity-bound SDC Files 3.6.5. Creating Clocks and Clock Constraints 3.6.6. Creating I/O Constraints 3.6.7. Creating Delay and Skew Constraints 3.6.8. Creating Timing Exceptions 3.6.9. Using Fitter Overconstraints 3.6.10. Example Circuit and SDC File
3.6.1. Recommended Initial SDC Constraints x
3.6.1.1. Create Clock (create_clock) 3.6.1.2. Derive PLL Clocks (derive_pll_clocks) 3.6.1.3. Derive Clock Uncertainty (derive_clock_uncertainty) 3.6.1.4. Set Clock Groups (set_clock_groups)
3.6.4. Using Entity-bound SDC Files x
3.6.4.1. Entity-bound Constraint Scope 3.6.4.2. Entity-bound Constraint Examples
3.6.5. Creating Clocks and Clock Constraints x
3.6.5.1. Creating Base Clocks 3.6.5.2. Creating Virtual Clocks 3.6.5.3. Creating Generated Clocks (create_generated_clock) 3.6.5.4. Deriving PLL Clocks 3.6.5.5. Creating Clock Groups (set_clock_groups) 3.6.5.6. Accounting for Clock Effect Characteristics 3.6.5.7. Constraining CDC Paths
3.6.5.1. Creating Base Clocks x
3.6.5.1.1. Automatic Clock Detection and Constraint Creation
3.6.5.2. Creating Virtual Clocks x
3.6.5.2.1. Specifying I/O Interface Uncertainty 3.6.5.2.2. I/O Interface Clock Uncertainty Example
3.6.5.3. Creating Generated Clocks (create_generated_clock) x
3.6.5.3.1. Clock Divider Example (-divide_by) 3.6.5.3.2. Clock Multiplexer Example
3.6.5.5. Creating Clock Groups (set_clock_groups) x
3.6.5.5.1. Exclusive Clock Groups (-logically_exclusive or -physically_exclusive) 3.6.5.5.2. Asynchronous Clock Groups (-asynchronous) 3.6.5.5.3. set_clock_groups Constraint Tips
3.6.5.6. Accounting for Clock Effect Characteristics x
3.6.5.6.1. Set Clock Latency (set_clock_latency) 3.6.5.6.2. Clock Uncertainty
3.6.6. Creating I/O Constraints x
3.6.6.1. Input Constraints (set_input_delay) 3.6.6.2. Output Constraints (set_output_delay)
3.6.7. Creating Delay and Skew Constraints x
3.6.7.1. Advanced I/O Timing and Board Trace Model Delay 3.6.7.2. Maximum Skew (set_max_skew) 3.6.7.3. Net Delay (set_net_delay)
3.6.8. Creating Timing Exceptions x
3.6.8.1. Timing Exception Precedence 3.6.8.2. False Paths (set_false_path) 3.6.8.3. Minimum and Maximum Delays 3.6.8.4. Multicycle Paths 3.6.8.5. Multicycle Exception Examples 3.6.8.6. Delay Annotation 3.6.8.7. Constraining Design Partition Ports
3.6.8.4. Multicycle Paths x
3.6.8.4.1. Common Multicycle Applications 3.6.8.4.2. Relaxing Setup with Multicycle (set_multicyle_path) 3.6.8.4.3. Accounting for a Phase Shift (-phase)
3.6.8.5. Multicycle Exception Examples x
3.6.8.5.1. Default Multicycle Analysis 3.6.8.5.2. End Multicycle Setup = 2 and End Multicycle Hold = 0 3.6.8.5.3. End Multicycle Setup = 2 and End Multicycle Hold = 1 3.6.8.5.4. Same Frequency Clocks with Destination Clock Offset 3.6.8.5.5. Destination Clock Frequency is a Multiple of the Source Clock Frequency 3.6.8.5.6. Destination Clock Frequency is a Multiple of the Source Clock Frequency with an Offset 3.6.8.5.7. Source Clock Frequency is a Multiple of the Destination Clock Frequency 3.6.8.5.8. Source Clock Frequency is a Multiple of the Destination Clock Frequency with an Offset
3.7. Timing Analyzer Tcl Commands x
3.7.1. The quartus_sta Executable 3.7.2. Collection Commands
3.7.2. Collection Commands x
3.7.2.1. Wildcard Characters 3.7.2.2. Adding and Removing Collection Items 3.7.2.3. Query of Collections 3.7.2.4. Using the get_pins Command
1. Answers to Top FAQs
2. Timing Analysis Introduction
3. Using the Intel® Quartus® Prime Timing Analyzer
A. Intel® Quartus® Prime Pro Edition User Guides

3.6.4.1. Entity-bound Constraint Scope

The entity-bound SDC approach offers diverse scoping possibilities for your constraints, each dictating the extent of their influence.
Table 20.  Entity-bound Constraint Scope
Constraint Scope Type Features To Enable Instance-bound Scoping
Automatic
  • Default mode applied to entity-bound SDC files defined in the Intel® Quartus® Prime Pro Edition GUI.
  • Under automatic scoping, constraints apply to every instance of the assigned entity across the project.
  • Each result from any get command (for example, get_pins, get_ports, and so on) in the SDC file is prepended with the instance's path.
  • All get commands are confined to the target elements within the bound instance associated with the SDC file.
Default mode for SDC_ENTITY_FILE. No additional steps required.
Manual
  • Accessible by QSF assignment only.
  • The -no_sdc_promotion setting disables automatic scoping, necessitating full hierarchical path for targeting nodes.
  • Grants the flexibility to target nodes beyond entity boundaries.
  • The get_current_instance command delivers the top-level path to the current instance, allowing you to merge filters targeting elements in the current instance with commands addressing those beyond entity boundaries.
Use -no_sdc_promotion. Append each collection filter with get_current_instance to target nodes within the entity boundaries.
For example: 
get_registers [get_current_instance]|reg[*]
Disabled
  • Accessible by QSF assignment only.
  • -no_sdc_promotion and the -no_auto_inst_discovery arguments together disable scoping, treating an entity-bound SDC as a global SDC file. The SDC file is read only once for the entire compilation instead of processing repeatedly for each instance it is linked to.
  • This mode is ideal when bundling an SDC with an entity destined for export as a qdb file, while preserving the capability for SDC's collection filters to specify global, top-level paths in their get commands.
Use -no_sdc_promotion and -no_auto_inst_discovery arguments.

When entity-bound SDC files are defined either through the graphical interface or via QSF assignments (excluding the -no_sdc_promotion and -no_auto_inst_discovery arguments), the constraints are applied using automatic scoping. Automatic scoping involves prepending filters with the instance's path. To provide clarity, the following table illustrates how paths are interpreted in various Tcl commands due to the automatic scoping of constraints:

Table 21.  Automatic Scope of Constraints
Constraint Example Auto-Scope Constraint Interpretation for Instance X|Y
set_false_path -from [get_keepers a] set_false_path -from [get_keepers X|Y|a]
set_false_path -from [get_registers a] -to [get_registers b] set_false_path -from [get_registers X|Y|a] -to [get_registers X|Y|b]
set_false_path –from [get_clocks clk_1] –to [get_clocks clk_2] set_false_path –from [get_clocks clk_1] –to [get_clocks clk_2]
set_max_delay –from [get_ports in] -to [get_registers A] 2.0 set_max_delay –from [get_ports in] -to [get_registers X|Y|A] 2.0
get_ports * get_ports *
get_clocks * get_clocks *
get_ports a get_ports a
get_clocks a get_clocks a

When automatic scoping is disabled through QSF assignments, including the use of the -no_sdc_promotion argument, you must manually prepend the top-level path to achieve the same behavior as automatic scoping. To simplify this process, use the -get_current_instance command as it returns the top-level path of the current instance. The following table illustrates how paths are interpreted when the -get_current_instance command is employed to add the top-level path to certain Tcl commands:

Table 22.  Manual Scope of Constraints
Constraint Example Manual Scope Constraint Interpretation 
set_false_path –from [get_current_instance]|d\ 
     –to [get_current_instance]|e
 
set_false_path –from i1|inner|d –to i1|inner|e 
set_false_path –from i2|inner|d –to i2|inner|e 
set_false_path –from i3|d –to i3|e
 
create_generated_clock –divide_by 2 –source \
   [get_ports inclk] –name \
   [get_current_instance]_divclk \
   [get_current_instance]|div 
set_multicycle_path –from [get_current_instance]|a \ 
   –to [get_current_instance]|b 2 
create_generated_clock –divide_by 2 –source \ 
    [get_ports inclk] –name “i1_divclk” i1|div 
set_multicycle_path –from i1|a –to i1|b 2 \ 
    create_generated_clock –divide_by 2 –source \ 
    [get_ports inclk] –name “i2_divclk” i2|div 
set_multicycle_path –from i2|a –to i2|b 2
Level Two Title