Constraining a Design

You can use a user constraints file (design_name.ucf) to control the implementation of your design. The user constraints file can contain information on where to place I/O pins and blocks of logic and timing requirements for the design.

If you want to control the implementation of your design with a user constraints file, you can specify this file in the Options dialog box. The software tries to implement your design to meet the specified timing requirements and other constraints.

To Specify a User Constraints File

1. Open the Options dialog box using one of the following methods.
   
   
   • From the Design Manager, select Design Implement. Click the Options button in the Implement dialog box.
     
     
   • From the Flow Engine, select Setup Options or click the Design Implementation Options toolbar button.
     
     
     
     The Options dialog box appears, as shown in the “Options Dialog Box” figure of the “Implementation Options” chapter.
     
     
2. In the Options dialog box, type the path to a user constraints file or click the User Constraints Browse button to open a file selection dialog box in which to specify a constraints file.
   
   
3. Click OK.
   
   When you implement the design, the Flow Engine uses the specified file to constrain the implementation.