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PPR 5.0: May ignore MAP=PLC on XC3000A CLBMAP symbols


Record #382

Problem Title:
PPR 5.0: May ignore MAP=PLC on XC3000A CLBMAP symbols


Problem Description:



Solution 1:




When floorplanning an XC3000A design, users may with to use CLBMAPs
in conjunction with the MAP=PLC property to lock CLB pins to a
specific location.

PPR may ignore the MAP=PLC attribute on CLB maps for 3000A designs.
The 'p' attribute will be passed through to the .MAP file correctly,
but PPR will ignore this in cases where there are two flip flops that
take inputs directly from nets outside the CLB, and neither net uses
the DI pin.

There is a workaround.	Insert a buffer feeding the D input of the flip-flop.
Place "X" flags on *both* the input and output nets of this buffer, and lock
the input of the buffer to the CLBMAP pin.  The "X" flags prevent XNFPREP
from trimming the buffer, and XNFMAP ignores the "X" on the buffer output
in order to obey the CLBMAP.





End of Record #382