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AR# 19778

6.1i XST - LOC constraint from XCF file ignored for bidirectional ports

Description

Keywords: XST, LOC, constraint, XCF, bidirectional

Urgency: Standard

General Description:
The LOC constraint from ".xcf" file or from HDL attributes is ignored for bidirectional ports.

In the following example:
io<3> is a bidirectional port.
o<3> is a unidirectional port - output

I have the following in my ".xcf" file:
BEGIN MODEL "sch1"
PIN "io<3>" loc=E4;
PIN "o<3>" loc=D1;
END;

XST shows the following in log:
Reading constraint file C:\examples\virtex2hdl\sch1.xcf.
Set user-defined property "LOC = E4" for signal <io<3>> in unit <sch1>.
Set user-defined property "LOC = D1" for signal <o<3>> in unit <sch1>.
XCF parsing done.

But in the ".pcf" file there is only one constraint.
SCHEMATIC START ;
// created by map version G.25a on Wed Nov 05 13:46:26 2003
COMP "o<3>" LOCATE = SITE "D1" LEVEL 1;
SCHEMATIC END ;

The io<3> LOC constraint is not passed to the ".pcf" file.

Solution

To work around this issue, specify the LOC constraints for bidirectional ports in the UCF file instead.
AR# 19778
Date Created 08/05/2004
Last Updated 03/08/2006
Status Archive
Type General Article