why warning "Missing drive strength" ?

[Altera_Forum]

Hello all, 

I am a beginner of Altera FPGA. Today I wrote a simple project with Quartus II 10.0. I set the device as EP3C25, then I wrote a simple VHDL, assigned the location and IO standard. When I compile this project, I always got a warning:"Some pins have incomplete I/O assignments. Refer to the I/O Assignment Warnings report for details". I check the assignment waring report, and all out pins are identified as "missing drive strength". I changed the device to EP1C12, reassign the location, the warning is eliminated. I did some tests, and found that if I use Cyclone III device, this warning will come out. Could anybody tell me why?

[Altera_Forum]

Drive strenght is the maximum current that the pin can drive. 

 In modern FPGA this is programmbale. If you don't set the value you get a warning saying that a default value (probably the highest current) has been set.   This is not a problem unless you don't have signal integrity problems  in the integration of your FPGA on the final board.   I think that when you don't get the warning is because the value is not programmable

[Altera_Forum]

Thank you. Could you tell how to program the drive strength?

[Altera_Forum]

--- Quote Start ---  Thank you. Could you tell how to program the drive strength?  --- Quote End ---    In the pin planner in the pin list there's a column called current strength. If it doesn't show up there, right-click your mouse in the pin list and select customize columns.... You can add the currenth strenght column and select the desired drive strength.  good luck, Ton

[Altera_Forum]

The warning is eliminated when I did what you told me to do.Thank you.