AR# 6492: 1.5i Virtex Map/PAR - Clock net LOC constraints may be ignored if IPAD to BUFG connection is used.
1.5i Virtex Map/PAR - Clock net LOC constraints may be ignored if IPAD to BUFG connection is used.
For the following configuration:
The .ucf NET constraint:
NET "NET_X" LOC=Y11 ;
is not handled successfully by the Map and PAR tools in version 1.5i.
Map incorrectly maps to a standard IOB rather than GCLKIOB and writes a LOC constraint into the .pcf file for the GCLKIOB site. PAR incorrectly ignores this invalid LOC constraint, so that there is no feedback to the user that the original .ucf constraint was ignored.
This problem is fixed in version 2.1i.
Meanwhile, the following configurations will work with the net constraint: