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AR# 12208

4.1i Virtex MAP - Registers that are LOC'd to slices end up in IOBs.

Description

Keywords: IOB, slice FF, register, LOC

Urgency: Standard

General Description:
My design contains several flip-flops that are range LOC'ed to a set of slice locations. However, in the NCD file produced by MAP, these flip-flops have been mapped into IOBs rather than slices. No warnings are printed about this, and the .pcf file produced by MAP is empty.

Solution

It was found that the flip-flops had IOB=TRUE attributes, which overrode the slice LOCs.

MAP will be changed in the next major release after 4.1i to warn about conflicts between LOC constraints and IOB attributes.
AR# 12208
Date Created 07/30/2001
Last Updated 08/20/2003
Status Archive
Type General Article