ISE
Changing Design Properties
Design properties control the target device, top-level source type, synthesis tool, simulation tool, compilation option, and Design Summary options for your design. You can update these settings as follows.
Caution! If you change the device information, generated files are deleted. This includes all synthesized netlists (for non-EDIF design flows), intermediate and output files of the implementation software, and reports. Source files and user constraints are not deleted.
To Change Design Properties
  1.  In the Hierarchy pane of the Design panel, select the device icon Image.
  2.  Select Project > Design Properties, or click the Edit Design Properties toolbar button Image.
  3.  In the Design Properties dialog box, edit the properties.
  4.  Click OK.

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