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AR# 21068

7.1i Virtex-4 PAR - "ERROR:Place:604 - Placer was unable to create LVDS pair for component ..."

Description

Keywords: PAR, LVDS, placer, placement, ERROR:Place:604

Beginning with version 7.1i, the I/O placer creates internal macros to better handle the automatic placement of LVDS pairs. This new macro causes problems if the designer LOCs the Master IOB to the Slave site and vice versa. This practice is unusual but valid.

"ERROR:Place:604 - Placer was unable to create LVDS pair for component clk_p due to the following reason:
ERROR:Place -
The following components are part of this structure:
IOB clk_p
IOB clk_n
The reason for this issue is the following:
All of the logic associated with this structure is locked and the relative
placement of the logic violates the structure. The problem was found between the
relative placement of IOB clk_p at site IOB_X0Y79 and IOB clk_n at site
IOB_X0Y78."

Solution

This problem has been fixed in the latest 7.1i Service Pack available at:
http://support.xilinx.com/xlnx/xil_sw_updates_home.jsp
The first service pack containing the fix is 7.1i Service Pack 2.

Meanwhile, a tactical patch is available to fix this. The fix allows LOC constraints to override the macro creation under environment variable control.

Windows:
http://www.xilinx.com/txpatches/pub/swhelp/ise7_updates/71isp1_par_win_21068.zip
To install, unzip in the XILINX install directory while maintaining directory
structure.

SET XIL_PAR_ALLOW_LVDS_LOC_OVERRIDE=1

Linux:
http://www.xilinx.com/txpatches/pub/swhelp/ise7_updates/71isp1_par_lin_21068.tar.gz
To install:
cd $XILINX
tar zxvf 71isp1_par_lin_21068.tar.gz

setenv XIL_PAR_ALLOW_LVDS_LOC_OVERRIDE 1

For more general information about setting ISE environment variables, see (Xilinx Answer 11630).

AR# 21068
Date Created 09/04/2007
Last Updated 10/19/2008
Status Archive
Type General Article