General Description: When doing a timing simulation on a Spartan-XL part from an FPGA Compiler generated XNF (.sxnf) netlist, there will be an extra inverter added to all LDPE primitives when using the .ngm file.
ソリューション
This problem has been found and will be fixed in the next 'quarterly' service pack. The work around is to not use the .ngm file during timing simulation.