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Posts: 824
Registered: ‎10-25-2012

How to assign pins in UCF file?

I am a beginner to use Xilinx FPGA. I try to use UCf file to do pin assignments. I just want to make whether I should use these commands:


NET "Pin1" LOC = A9;


What is the mean of the first command? 


And whether these commands work for both Verilog and VHDL design? If somebody can give a link to show demos in UCF constrain, that will be great.


Thanks very much.

Posts: 8,355
Registered: ‎07-21-2009

Re: How to assign pins in UCF file?

Have you read the sticky README thread in the New Users Forum?  There should be links to tutorials for beginners, which may be helpful to you.


I use a text editor for editing .UCF file.  The PLANAHEAD program is a glossy windows app for editing the signal and location constraints ad assignments in the .UCF file.  You will most likely prefer.Planahead.  There is a user manual for Planahead, I believe.


The first line specifies a signaling standard for the IO signal named "Pin1".  The signaling standard is 2.5V Low Voltage CMOS.  If you look in the IO User Guide for the device family you are using, you should see descriptions of the available signaling standards.


The.UCF file uses a Xilinx-developed syntax which is neither Verilog nor VHDL.


-- Bob Elkind

README for newbies is here: http://forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369

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Posts: 824
Registered: ‎10-25-2012

Re: How to assign pins in UCF file?

Thanks very much, I will read the README thread. I prefer to edit UCF file directly in ISE instead of using PlanAhead to do pin assignments. Is that all constrains for Xilinx FPGA design can be wrote in UCF file ( like time constrain) ?. What is the difference between UCF and XCF?

Xilinx Employee
Posts: 2,501
Registered: ‎08-13-2007

Re: How to assign pins in UCF file?

[ Edited ]

ucf is for implementation, e.g. ngdbuild/translate.

xcf is an optional constraint for file XST synthesis.


You may find this useful:

http://www.xilinx.com/support/documentation/sw_manuals/xilinx14_2/cgd.pdf (Xilinx Constraints Guide)




Posts: 129
Registered: ‎01-04-2009

Re: How to assign pins in UCF file?

It means that if you are not very careful and FULLY understand the relationship between *.ucf /VHDL/ Verilog and outside world.

you can destroy your FPGA!!!!