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AR# 15426

5.2i XST - XST incorrectly compares signed constants and generates incorrect logic

Description

Keywords: XST, VHDL, compare, comparison, incorrect, wrong, logic, signed, unsigned

Urgency: Urgent

General Description:
When performing comparisons on signed constants, XST generates incorrect logic.

Solution

You can work around this problem by using only the unsigned package. A patch is available specifically for this problem. This patch works only with the 5.2i Service Pack 3.

To resolve this issue, apply the following platform-appropriate patch to the ISE 5.2i SP3 installation:
http://www.xilinx.com/txpatches/pub/swhelp/ise5_updates/xst_patch_nt_5203i.zip
http://www.xilinx.com/txpatches/pub/swhelp/ise5_updates/xst_patch_sol_5203i.tar.gz
http://www.xilinx.com/txpatches/pub/swhelp/ise5_updates/xst_patch_sol64_5203i.tar.gz

To install the patch, unzip the contents into the appropriate directory as follows:
Solaris: $XILINX/bin/sol
Solaris64: $XILINX/bin/sol64
Windows: %XILINX%\bin\nt
AR# 15426
Date Created 08/18/2002
Last Updated 10/20/2005
Status Archive
Type General Article