In the timing report, there are no user constraints but only "Default ..." constraints like the following. What is the problem?
Default period analysis for net "cpu_clk"
Default OFFSET IN BEFORE analysis for clock "cpu_clk"
Default OFFSET OUT AFTER analysis for clock "cpu_clk"
This is because the -a option of Timing Analyzer is enabled when generating the timing report. When the -a(advanced analysis) option is used, Timing Analyzer will ignore any user constraints in the UCF and perform automatic timing analysis. This is why there are only "Default..." constraints in the timing report.This option is only used if you are not supplying any timing constraints (from a PCF) to TRACE. When user wants to generate the timing report based on user constraints, the -a option should not be used.