How do I simulate low lovel entities?

[Altera_Forum]

I'm working on some basic units (low level entities) which I'll later use to build the top level with. 

 When I opened the project I had to give the top level entity a name, and so I did. But now I cant compile and simulate the low level entity I created because it keeps asking for the top level.  Another question is ho do I handle several low level entities? I wish to create them in the same project but to compile and simulate them each one alnoe at first. How do I do this ?  Thanks.

[Altera_Forum]

see: http://www.alteraforum.com/forum/showthread.php?t=21911

[Altera_Forum]

Thanks for your quick help.  

Can I compile one file only or is compilation, by default, includes all the files in the project ?

[Altera_Forum]

i think Analysis and Elaboration will go through all the files in the project, but synthesis (and the rest of the compile) will only use what elaboration found to be necessary to compile the project. so your syntax should still be correct in the files that are in the project but not actually used in the design or else compilation will error out. the logic in the unused files won't show up in resource usage or anything.

[Altera_Forum]

You can compile any entity at any time provided you set them as top level entity. I do not know which simulation tool you use. But in general you can simulate any low level entity. If you are simulating top level the low level entity must be precompiled before you do the top level. Check your simulation tool user guide.

[Altera_Forum]

--- Quote Start ---  You can compile any entity at any time provided you set them as top level entity. I do not know which simulation tool you use. But in general you can simulate any low level entity. If you are simulating top level the low level entity must be precompiled before you do the top level. Check your simulation tool user guide.  --- Quote End ---   good point, if you simulate in ModelSim-AE directly you can just vcom the appropriate files and vsim the correct top.  i usually edit the Quartus/Nativelink ModelSim .do to taste, out of laziness. ;)