Error: top level design entity " " is undefined

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hello, I met with the same question,

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As FvM indicated this error message is caused by the fact that no VHDL entity is found with the name of the "top level entity". It is not enough to name your VHDL file with the name of the top entity. The top entity itself of your VHDL description should have this name.

e.g. In the example below TOP is the "Top Level Entity" and has been declare d like that (see @pletz) file TOP.vhd

entity TOP is

port (

...

);

end TOP;

architecture my_design of TOP is

begin

...

end my_design;