read physical and timing constraints from one of more files.
Syntax
read_xdc [‑cells <args>] [‑ref <arg>] [‑quiet_diff_pairs] [‑mode <arg>]
[‑unmanaged] [‑no_add] [‑quiet] [‑verbose] <files>
Returns
List of files.
Usage
Name | Description |
---|---|
[-cells]
|
Import constraints for these cells |
[-ref]
|
Import constraints for this ref |
[-quiet_diff_pairs]
|
Suppress warnings about differential pair inference when importing I/O ports |
[-mode]
|
Import constraints as out_of_context. Values: default, out_of_context Default: default |
[-unmanaged]
|
treat this file as unmanaged constraints file |
[-no_add]
|
don't add this file to constraints fileset |
[-quiet]
|
Ignore command errors |
[-verbose]
|
Suspend message limits during command execution |
<files>
|
Input file(s) to read |
Categories
Description
Imports physical and timing constraints from a Xilinx™ Design Constraints file (XDC). The XDC is imported into the current_instance
level of the design hierarchy, which defaults to the top-level of the design, or can be imported into specified cells. When imported at the top-level, the specified XDC file is added to the active constraint fileset.
This command is similar to the add_files
command in that the XDC file is added by reference rather than imported into the local project directory.
You can use this command to read the contents of source files into the in-memory design, when running the AMD Vivado™ Design Suite tool in Non Project mode, in which there is no project file to maintain and manage the various project source files. Refer to the Vivado Design Suite User Guide: Design Flows Overview (UG892) for more information on Non Project mode.
Arguments
-cells
<args> - (Optional) Apply the constraints from the XDC file to the specified instance names. The constraints will be applied ONLY to the specified cell instances, and the XDC file will not be added to the active constraint fileset.
-ref <arg>
- (Optional) Read the constraints from the XDC file and apply them to ALL instances of the referenced module, wherever they happen to be instantiated in the current design.
-quiet_diff_pairs
- (Optional) Suppress warnings about differential pair inference when importing I/O constraints.
-mode [ default | out_of_context ]
- (Optional) Import the specified constraint files as in-context with the top-level design, or as out_of_context constraints to be used when generating output products for hierarchical modules or IP cores. For more information on the out-of-context design flow, refer to the Vivado Design Suite User Guide: Design Flows Overview (UG892).
-unmanaged
- (Optional) Treat the added files as unmanaged Tcl constraint files. The Vivado tool will not save constraint changes back into these unmanaged Tcl files. For more information on unmanaged Tcl constraints, refer to the Vivado Design Suite User Guide: Using Constraints (UG903).
-no_add
- (Optional) Read the constraints from the file, and integrate them into the in-memory design, but do not add the XDC file to the list of files in the current constraint set.
-quiet
- (Optional) Execute the command quietly, returning no messages from the command. The command also returns TCL_OK regardless of any errors encountered during execution.
-verbose
- (Optional) Temporarily override any message limits and return all messages from this command.
set_msg_config
command.
<files>
- (Required) The filenames of the XDC files to be imported.
Examples
The following example reads the XDC file and applies it to the current design:
read_xdc file_1.xdc
The following example reads the XDC file and applies it ALL instances of the referenced module found in the current design:
read_xdc -ref hex2led file_2.xdc
The following example reads the XDC file and applies it ONLY to the specified instance within the referenced module:
read_xdc -ref sixty -cells lsbcount file_3.xdc
The following example reads the XDC file and applies it to the specified instances in the current design, even though they are instances of different modules:
read_xdc -cells {one_decode sixty/msbcount} file_4.xdc