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1keith1
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Registered: ‎02-17-2014

XST trimming I/O signals

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I'm getting constraint errors similar to the one in this solution: http://www.xilinx.com/support/answers/34900.html Where the tool doesn't think the I/O signals are drivers or loads and so it removes them.

I've tried modifying the system_xst.scr file and setting '-iobuf YES' where previously it was set to NO, but this still doesn't solve my problem. I did this according to this solution: http://www.xilinx.com/support/answers/52274.html

What else can I do to prevent these signals from being trimmed? Do I just need to use the KEEP commands on my ucf?

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1keith1
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Registered: ‎02-17-2014

Update: 
I wasn't able to resolve this so I just created a new project, in the same way, and now these errors/warnings are gone.

 

 

View solution in original post

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balkris
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Registered: ‎08-01-2008
The work-around is to instantiate IBUF and OBUF in the HDL code manually.
Thanks and Regards
Balkrishan
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htsvn
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Registered: ‎08-02-2007

hi,

 

would that be possible to let us know if the error is on the top-level signals or internal signals?

are these signals driving/or being driven by any logic?

 

--hs

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1keith1
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Here is a photo of the errors:

Capture.PNG

 

These signals are at the top level, listed as external ports:

Capture1.PNG

 

Yes they are driving logic, a TEMAC hard core and a DDR2 controller. This is on a virtex 5.

 

On my system.v file I have:

...
 (* KEEP = "TRUE" *) input xps_ll_temac_0_RGMII_RX_CTL_0_pin;
(* KEEP = "TRUE" *) input [3:0] xps_ll_temac_0_RGMII_RXD_0_pin;
(* KEEP = "TRUE" *) output xps_ll_temac_0_TemacPhy_RST_n_pin;
(* KEEP = "TRUE" *) output [3:0] xps_ll_temac_0_RGMII_TXD_0_pin; ...

and in my system.ucf I have:

NET xps_ll_temac_0_TemacPhy_RST_n_pin                         LOC = G38 | IOB = true | KEEP;
NET xps_ll_temac_0_RGMII_TXD_0_pin<0>                         LOC = R38 | IOB = true | KEEP;
NET xps_ll_temac_0_RGMII_TXD_0_pin<1>                         LOC = P38 | IOB = true | KEEP;
NET xps_ll_temac_0_RGMII_TXD_0_pin<2>                         LOC = N38 | IOB = true | KEEP;
NET xps_ll_temac_0_RGMII_TXD_0_pin<3>                         LOC = M38 | IOB = true | KEEP;

 

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1keith1
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Registered: ‎02-17-2014

Update: 
I wasn't able to resolve this so I just created a new project, in the same way, and now these errors/warnings are gone.

 

 

View solution in original post

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