An ASCII text file (with the extension .tdf) written in the Altera Hardware Description Language (AHDL).
A TDF can contain any combination of Boolean equations, truth tables, state machines, and group operations. TDFs can also be parameterized.
You can easily incorporate Altera-provided primitives and both Altera-provided megafunctions and user-defined megafunctions and macrofunctions, including library of parameterized modules (LPM) functions, into a TDF. You can use a megafunctino or macrofunction by creating a Function Prototype and inserting an instance of the function into the Text Design File. You can also use this method to incorporate Text Design File logic in another Text Design File. You can also automatically generate a default AHDL Include File (.inc) that contains a Function Prototype for any design file. To do so, on the File menu, point to Create/Update and click Create AHDL Include Files for Current File.
Text Design Files can be incorporated into both top-level entities and lower-level entities in a project. To direct the Quartus II software to automatically create a Block Symbol File (.bsf) that represents any design file, on the File menu, point to Create/Update and click Create Symbol Files for Current File. This symbol and the logic it represents can be incorporated into a Block Design File (.bdf).
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