The Constraints Editor does not include the LVTTL and LVCMOS33 standards for Spartan-3. These standards do not appear in the GUI pull-down menu in the Constraints Editor.
To work around this issue, perform one of the following:
- Run PACE (or click on "Assign Package Area" within ISE); these standards are available in PACE.
- Add the constraints manually in the FPGA Editor.
This issue is fixed in the 6.1i software release, which is scheduled for release September 2003.