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AR# 9344

3.1i Virtex MAP - Some eligible registers are not being packed into IOBs.


Keywords: registers, flops, FFs, -pr ,IOB=TRUE, IOB

Urgency: Standard

General Description:
A case has been seen where 3.1i MAP, when run with the switch "-pr b,"
did not pack as many registers into IOBs as it was able to in 2.1i.



This problem is fixed in the latest 3.1i Service Pack available at:
http://support.xilinx.com/support/techsup/sw_updates/. The first
service pack containing the fix was Service Pack 1.


This problem can be worked around by assigning the same
BLKNM attribute to all comps that belong in the same IOB.
The following is an example of UCF syntax:

INST "pad_name" BLKNM = "IOB1" ;
INST "ibuf_name" BLKNM = "IOB1" ;
INST "inreg_name" BLKNM = "IOB1" ;

AR# 9344
Date Created 05/23/2000
Last Updated 08/19/2002
Status Archive
Type General Article