Description

Solution

Some XST constraints can be applied not only globally but also specifically to certain modules, instances or signals in the XST Constraint File (XCF). Most XST constraints that can be applied in RTL code can also be applied in XCF. Applying constraints in the XCF makes the HDL source code more portable and reusable.

Following are some examples of applying XST constraints in XCF.

BEGIN MODEL "top"
NET "signal1" fsm_style = lut;
END;

MODEL "top" keep_hierarchy = yes;

BEGIN MODEL "top"
INST"submodule1"shift_extract = no;
END;

For more information about any constraints syntax in XCF, please refer toUG627/687-XST User Guide (Xilinx Answer 38931).

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