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Visitor gilg
Visitor
71 Views
Registered: ‎12-29-2016

IBERT GTREFCLK from MMCM

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Hello,

I'm integrating IBERT core into Kintex160 FPGA using Vivado 2018.2 

According to Xilinx wrapper example, GTREFCLK input of the IBERT core is connected to GTREFCLK0P/N pins using IBUFDS_GTE2 cell.

This works fine, however I want to drive GTREFCLK from MMCM output and get the following message:

ERROR: [DRC REQP-56] connects_GTGREFCLK_ACTIVE: GTXE2_COMMON cell u_ibert_core/inst/QUAD[1].u_q/u_common/u_gtxe2_common: Use of the GTGREFCLK is reserved for test purposes only. This has the lowest performance of the available clocking methods and can degrade transceiver performance. Note that GTGREFCLK use may be caused by driving a REFCLK with a BUFG.

Is there a way to drive GTREFCLK from MMCM/PLL instead of pins?

 

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Moderator
Moderator
56 Views
Registered: ‎07-30-2007

Re: IBERT GTREFCLK from MMCM

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You can't drive the reference clock from the MMCM.  There is too much jitter on the fabric clocks.  It would be inefficient and prohibitively expensive to make the fabric clocks meet MGT standards.  The GTGREFCLK input is for Xilinx internal testing.

Roy


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Moderator
Moderator
57 Views
Registered: ‎07-30-2007

Re: IBERT GTREFCLK from MMCM

Jump to solution

You can't drive the reference clock from the MMCM.  There is too much jitter on the fabric clocks.  It would be inefficient and prohibitively expensive to make the fabric clocks meet MGT standards.  The GTGREFCLK input is for Xilinx internal testing.

Roy


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Don't forget to reply, kudo, and accept as solution
----------------------------------------------------------------------------


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