AR# 44282: 13.2 XST - Derived constraints for MMCM are not taken into consideration during optimization
AR# 44282
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13.2 XST - Derived constraints for MMCM are not taken into consideration during optimization
描述
XST derives constraints for MMCM output clocks, but it does not take the constraints into consideration when performing optimization.
解决方案
XST is deriving the constraints for the outputs, but it is not taking the derived constraints into consideration when performing optimization which results in more logic paths. XST should be performing this automatically.
To work around the issue, put the derived constraints into an XCF file and this will force XST to optimize the design using the constraints.
A CR has been filed for better optimization using automatic derived constraints.