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

ID 683243
Date 10/02/2023
Document Table of Contents 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
  • 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.
  • 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[*]
  • 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 \
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