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Visitor trl
Registered: ‎10-01-2018

Ultrascale GTH RX: How to use recovered clock as GTH RX reference clock source


I am using Ultrascale GTH RX core.

I am trying to use the GTH RX recovered clock to drive MGTREFCLK, through external pins and jitter attenuation.

But there is no clock signal output on RXRECCLKOUT port if I don't provide a clock to MGTREFCLK first.

How to generate RX recovered clock if I don't provide a clock to MGTREFCLK first?

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Registered: ‎05-02-2017

Re: Ultrascale GTH RX: How to use recovered clock as GTH RX reference clock source

HI @trl,


Generally is it recommended to use the external clock source for generating the MGTREFCLK  , since Each Quad has two dedicated differential reference clock input pins (MGTREFCLK0[P/N] or MGTREFCLK1[P/N]) that can be connected to the external clock sources. In a single external reference clock use model, an IBUFDS_GTE3/4 must be instantiated to use one of the dedicated differential reference external clock sources and In the multiple external reference clocks use model, each dedicated reference clock pin pair must instantiate its corresponding IBUDFS_GTE3 primitive to use these dedicated reference external clock resources.

since Upon device configuration, the clock output from the IBUFDS_GTE3/4 which takes inputs from MGTREFCLK[0/1]P and MGTREFCLK[0/1] is driven to the PLL's hence you have to provide the MGTREFCLK  first in-order to generate the RX recovered clock. once the Recovered clock is generated then is used since The reference clock structure in the GTH transceiver supports two modes of operation: input mode and output mode. In the input mode of operation, your design provides a clock on the dedicated reference clock I/O pins that is used to drive the Quad or channel PLLs. In
the output mode of operation, the recovered clock (RXRECCLKOUT) from any of the four channels within the same Quad can be routed to the dedicated reference clock I/O pins. This output clock can then be used as the reference clock input at a different location. The mode of operation cannot be changed during run-time.












Chandra sekhar
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