Constraints generated by System Generator fail in XST with the following error message:
"ERROR:Xst:1587 - Line 10: No signal name matches ce_1500_sg_x7 pattern."
Where "ce_1500_sg_x7" is a clock enable signal verified by me in the RTL code created by System Generator.
This is a known issue caused by XST renaming the signal prior to attaching the constraint to it. To work around this issue, you must apply some attributes to the signal so it will not be renamed.
In the top-level output from System Generator, you should see the following lines that declare the attributes for use:
attribute syn_keep: boolean;
attribute keep: boolean;
attribute preserve_signal: boolean;
Add the following lines to apply these attributes to the appropriate signal that is being renamed (in this case, ce_1500_sg_x7 is the target signal):
attribute syn_keep of ce_1500_sg_x7: signal is true;
attribute keep of ce_1500_sg_x7: signal is true;
attribute preserve_signal of ce_1500_sg_x7: signal is true;
As of System Generator for DSP 9.2, these attributes are automatically added to the HDL netlist.