When running the Implementation phase in ISE 10.1 using ChipScope cores that were generated in previous versions of the software, MAP fails with "ERROR:LIT" messages. What is the problem?
ChipScope cores generated pre-10.1 contain SAVE constraints in the "ila.ncf" files. When running these through ISE 10.1 implementation design tools, seemingly unrelated LIT and MapLib errors might occur due to data or trigger signals evaluating to a constant. To work around this issue:
1. Regenerate the ChipScope core using the CORE Generator flow in ISE 10.1.
2. Remove the SAVE constraint from the ".ncf" files. See the following for SAVE constraint example.
NET "<net_name>" S;
This issue is resolved in ISE 10.1 Service Pack 1. Removing the SAVE constraint will be automated in MAP.