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AR# 1567

XC3000/XC4000/XC52000, XACT 5.2- XNFMERGE: An "S" attribute attached to an OBUF output at the top level is dropped



Urgency: Standard

General Description:
XNFMERGE drops "S" attributes that are attached to the output signal of a sourceless OBUF, causing XNFPREP to trim out the component.

When the SAVE flag (S attribute) is attached to a signal, XNFPREP is simply instructed to not remove the signal on its first trimming pass just because its pins are sourceless or loadless. However, if any logic related to the signal's source or destination is optimized to VCC or GND, the signal will be removed. This should not depend on whether or not the signal is an actual output port.

This property is dropped by XNFMERGE due to a bug.


To work around this problem, attach the "S" property to the INPUT of the OBUF rather than the output.
AR# 1567
Date Created 08/31/2007
Last Updated 01/12/2003
Status Archive