Scoping Constraints - 2022.1 English

The XDC files that an IP delivers are scoped to the IP instance(s) using two properties on the XDC file(s):

For more information on these properties see Vivado Design Suite User Guide: Using Constraints (UG903).

When overriding IP constraints at the top-level you have two choices:

• Specify the hierarchy to specific cell of the IP. If there are multiple instances of the IP, do either of the following:
  • Use wild cards
  • Duplicate the constraint for each IP
• Use the SCOPED_TO_REF and SCOPED_TO_CELLS properties that the IP uses and write your constraints as if the IP cell were the top-level of the hierarchy (recommended).

To find the SCOPED_TO_REF and SCOPED_TO_CELLS values you can use the report_compile_order -constraints command. Look at the synthesis or implementation section for the IP fileset.

The SCOPED_TO_REF is typically the IP customization name. The SCOPED_TO_CELLS is typically either inst in Verilog or U0 in VHDL.

Xilinx recommends you create a new XDC or Tcl file and place all the XDC/Tcl commands to override the IP XDC and set the SCOPED_TO_REF and SCOPED_TO_CELLS properties to match what 1 lists.

The complete procedure is, as follows:

1. Create a new XDC or Tcl file and add it to your active constraint set.
2. Place any XDC or Tcl commands required to override the IP XDC in the new file.
3. Use the set_property command to set the SCOPED_TO_REF and SCOPED_TO_CELLS properties:

   set_property SCOPED_TO_REF <REF> [get_files <new XDC/Tcl file>]
   set_property SCOPED_TO_CELLS <CELL> [get_files <new XDC/Tcl file>]

4. Mark the XDC/Tcl file to be used in implementation only:

   set_property USED_IN IMPLEMENTATION [get_files <net XDC/Tcl file]