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AR# 8879

10.1 Timing/Constraint - I am not able to apply a PERIOD constraint for OFFSET constraints on shift register LUTs

Description

If I try to apply a PERIOD constraint for an OFFSET OUT/BEFORE constraint on a shift register LUT that is being used as part of a chain, a fatal error reports that the PERIOD constraint cannot be found.

(If the design uses only the shift register as part of a chain, and the last stage is packed into the slice with the previous stage, TRACE will not be able to validate the D input of that BEL as a path endpoint.)

解决方案

Currently, you can work around this issue by not applying an OFFSET OUT/BEFORE constraint on a shift register LUT that is being used as part of a chain for Virtex-II.

For more information, please also see (Xilinx Answer 5489).

This issue is fixed in the 11.1 release of the software.

AR# 8879
创建日期 08/21/2007
Last Updated 12/15/2012
状态 Active
Type 综合文章