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AR# 21636

7.1i XST - "Packer Warning: LUT driving carry cannot be packed due to conflict with the common signal requirement between the LUT inputs and the Carry DI/MAND pins. This would result in an extra LUT for a feedthrough."

Description

Keywords: XST, packer, carry, conflict, common, LUT, signal, requirement, feedthrough, DI, MAND

Urgency: Standard

General Description:
When trying to run synthesis on a design, XST writes out warnings such as the following during the optimization stage:

PACKER Warning: Lut figc1/transmitter_interface/transmitter__n0767<1>lut driving carry figc1/transmitter_interface/transmitter__n0767<1>cy can not be packed with the carry due to conflict with the common signal requirement between the LUT inputs and the Carry DI/MAND pins. This would result in an extra LUT for a feedthrough.

Solution

This warning is not supposed to be there in the software. It is a debug message, and it should not be displayed to the user. The warning can be safely ignored; also, beware that there will be an estimation error in the number LUT resource utilization by XST.

This issue will be fixed in ISE 8.1i
AR# 21636
Date Created 06/22/2005
Last Updated 12/16/2008
Status Archive
Type General Article