When I use the Schematic Editor in either WebPACK or ISE, sometimes I want to lock down my pins on the schematic rather than using a UCF file. How do I do this?
Follow these steps to add pin locations to the schematic:
1. Right-click the I/O marker or the net connected to it, and select "Object Properties."
2. Click the "New" button to add a new net attribute.
3. Enter "LOC" for the attribute name and the pin name (e.g., P14 or A21) for the value, then click "OK."
4. Click "OK" once more from the Object Properties dialog box to return to the schematic.
5. To view the location constraint on the schematic, go to the Add -> Attribute Window. In the Attribute Name option box, type "LOC." Finally, click the net for which you want to see the LOC attribute.