UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

cancel
Showing results for 
Search instead for 
Did you mean: 
Highlighted
Voyager
Voyager
3,012 Views
Registered: ‎05-30-2017

LOC XST constraint with wildcard

Jump to solution

Hello,

I'm currently working on a design with Spartan 6 xc6slx150t-3fgg900, using ISE 14.7 and Verilog language. It is correct to write in a .v a constraint with the wildcard for example ( *LOC = "ILOGIC_X*Y*) or the wildcard can be used only in the .ufc? Thank you.

0 Kudos
1 Solution

Accepted Solutions
Historian
Historian
5,299 Views
Registered: ‎01-23-2009

Re: LOC XST constraint with wildcard

Jump to solution

So, yes, it appears to be legal syntax, although I have never seen anyone use it.

 

Nonetheless, the "correct" way to force a flip-flop into the IOB is using the IOB property I described, not a LOC constraint with a wildcard.

 

Avrum

4 Replies
Historian
Historian
3,000 Views
Registered: ‎01-23-2009

Re: LOC XST constraint with wildcard

Jump to solution

No. You cannot do this. It is not even legal in the UCF file; the LOC location must be a string with no wildcards.

 

If you want to force a flip-flop into the IOB (which is what the ILOGIC is), set the IOB=TRUE (or IOB=FORCE) property on the flip-flop. This CAN be done in the RTL.

 

(* IOB = "FORCE") reg my_iob_ff;

 

always @(posedge clk)

begin

  my_iob_ff <= (whatever);

end

 

This will force the flip-flop my_iob_ff into the IOB.

 

Avrum

Voyager
Voyager
2,912 Views
Registered: ‎05-30-2017

Re: LOC XST constraint with wildcard

Jump to solution

@avrumw,

thank you for the reply. Looking at https://www.xilinx.com/support/documentation/sw_manuals/xilinx11/cgd.pdf pg 124 it seem that using wildcards in LOCATION constraints in the .ucf file it is legal. What do you think? Thank you.

0 Kudos
Historian
Historian
5,300 Views
Registered: ‎01-23-2009

Re: LOC XST constraint with wildcard

Jump to solution

So, yes, it appears to be legal syntax, although I have never seen anyone use it.

 

Nonetheless, the "correct" way to force a flip-flop into the IOB is using the IOB property I described, not a LOC constraint with a wildcard.

 

Avrum

Voyager
Voyager
2,860 Views
Registered: ‎05-30-2017

Re: LOC XST constraint with wildcard

Jump to solution

Thank you for the reply. I used the LOC constraint with wildcard because I wanted to force FFs and latches specifically in ILOGIC blocks. Thanks for the help!

0 Kudos