Xilinx Answer #6766 : Virtex: IOB registers clocked by the CLKDLL still use the delay elements on the data path, this will cause longer SETUP delay.

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Virtex: IOB registers clocked by the CLKDLL still use the delay elements on the data path, this will cause longer SETUP delay.

Record #6766
Product Family: Hardware

Product Line: Virtex

Product Part: Virtex General Hardware

Problem Title:
Virtex: IOB registers clocked by the CLKDLL still use the delay elements on the data path, this will cause longer SETUP delay.

Problem Description:
Urgency: Standard

Input registers that are packed into the IOB and clocked from a CLKDLL
still use the DELAY element on the data pat. This will lead to excessive input
setup delay.

Currently no WARNING is issued by the tools when the DELAY element is not turned off. This problem occurs in m1.5i, m1.5iSP1, m1.5iSP2. description:

Solution 1:

To workaround this problem, add the NODELAY attribute to the input register clocked by CLKDLL. This can be done in the UCF file or the NCF file by using the following format:

NET RcvData* NODELAY ;
NET SelectOUT NODELAY ;

End of Record #6766 - Last Modified: 06/15/99 09:37

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