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AR# 342

XNFPREP 5.0:Pins on CLB primitives are always locked and unswappable


When XNFPREP 5.0 encounters a CLB primitive, it breaks it down into gates and
flip-flops, and adds a CLBMAP to the netlist so that the resulting logic is
placed in one CLB. Additionally, it always adds the property MAP=PLC to the
CLBMAP instances. This specifies that the pins on the CLB are locked and
closed, which means that the pins may not be swapped, nor logic added to the
CLB. This is done regardless of whether there a 'P' attributes on the pins of
the CLB primitive ( the 'P' attribute is used to lock individual pins ). There
are two potential workarounds:

* In an XC2000/XC3000 family design, the `lock pin' statements can be removed
from the SCP file in between MAP2LCA and APR. If there are no `real' pin
locks in the design, this is straightforward; if there are any real pins
locks, it could be quite confusing.

* In any flow, the XTF file could be edited between XNFPREP and XNFMAP.
The MAP=PLC parameter should be changed to MAP=PUC or deleted. If there are
no user-defined MAP=PLC parameters in the design, this could be a simple
search-and-replace. Otherwise, only modify those CLBMAPs which have the
SYSTEM=XNFTRIM property on them. These are the ones that have been expanded
from CLB/IOB primitives.

AR# 342
Date 03/31/1997
Status Archive
Type ??????