ISE
Instantiation and Inference
Instantiation and inference are two different methods of adding components to your design, and each method has its advantages. Instantiation gives you full control over how the component is used, therefore, you know exactly how the logic will be used. Inference offers readable and portable code that can be used to target different architectures.
Note For information on specific components, see Components Overview. For information about all design components see the Libraries Guides, available from the Software Manuals collection.
Instantiation
When you instantiate a component, you add an instance of that component to your HDL file or schematic. Xilinx® provides the following methods for instantiating components:
  •  HDL
    In an HDL file, you must use specific syntax to instantiate a component. For your convenience, the ISE® software provides Language Templates, which are pre-built code examples that you can insert into your own design file. You can also create and store your own User Templates. For information, see Working with Language Templates.
    You can also use instantiation templates. For more information on instantiation templates, see the XST User Guide, the Synthesis and Simulation Design Guide, or your third party synthesis software documentation.
  •  Schematic
    In a schematic file, you can instantiate components from the Xilinx® Unified Library provided with the ISE software. You can also create your own schematic symbols to instantiate. For information, see the Schematic Overview.
Black Box Instantiation
A "black box" is a module that you instantiate but that does not require a corresponding source file during synthesis. However, you must make the source of your black box available during the Translate process so the software tools (NGDBuild) can resolve the black box. An example of a black box is an Intellectual Property (IP) core that references an EDIF or NGC netlist.
Inference
When you infer a component, you provide a description of the function you want to accomplish. The synthesis tool then interprets the HDL code to determine which hardware components to use to perform the function. For your convenience, the ISE software provides Language Templates, which are pre-built code examples that you can insert into your own design file. You can also store your own User Templates. For information, see Working with Language Templates.
You can also use inference templates. For more information on inference templates, see the XST User Guide, the Synthesis and Simulation Design Guide, or your third-party synthesis software documentation.
Note  Not all components can be inferred. In this case, the component must be instantiated.
See Also

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