Answers Database
Foundation Express F1.5: When are constraints applied from the Express Constraints Editor?
Record #4880
Product Family: Software
Product Line: Synopsys
Product Part: Foundation Express API
Problem Title:
Foundation Express F1.5: When are constraints applied from the Express Constraints Editor?
Problem Description:
Urgency: Standard
General Description:
Foundation Express users have the ability to use the FPGA Express Constraints
Editor to enter physical and timing constraints for the design. This solution
provides more detail about how and when these constraints are applied.
The first thing to note is that the Express Constraints Editor will not export
timing constraints by default. Physical constraints (pin locations, slew rate,
pullup usage, clock buffers, etc.) will always be applied when entered, but
timing specifications (written as TIMESPECs in the XNF or NCF (Virtex only))
will only be written if that option has been enabled by the user. To enable
this option, select Synthesis->Options within the Foundation Project Manager
and check the box next to "Export Timing Constraint".
Solution 1:
To access the Express Constraints Editor, check the box next to "Edit
Synthesis/Implementation Constraints" when Synthesizing the design. This will
prompt the Express Constraints Editor to open after the elaboration phase of
synthesis has completed. You can also open the Constraints Editor on a Version
that has already been synthesized by right-clicking the Functional Structure
(under the Versions tab) and selecting "Edit Constraints..."
Each synthesis run is represented by a Version in your Foundation project.
Constraints entered in the Express Constraints Editor are applied only to that
particular Version.
If you use the "Update" command to re-synthesize and re-optimize an existing
Version, the constraints will remain and apply to that Version. The Update
command is used by right-clicking on the Functional Structure or Optimized
Structure and selecting "Update".
If you want to take constraints entered in one Version and apply them to
another Version, you must use the "Export Constraints" and "Import Constraints"
buttons. In the first Version, select the Functional Structure, right click
and select "Edit Constraints". Click the "Export Constraints" button to save
the constraints in an .EXC file. Then, when synthesizing the new version, open
the Constraints Editor and click on the "Import Constraints" button and select
the .EXC file saved earlier.
Express will apply any constraints it can, but realize if instances or names
have changed in the source HDL, Express will not be able to match constraints
relating to the modified instances.
End of Record #4880 - Last Modified: 10/22/98 14:56 |
