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SJadh1's avatar
SJadh1
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7 years ago

What is rx_pma_iqtxrx_clkout signal ?

Hello, I am working on a design with transceiver. I would like to know what is rx_pma_iqtxrx_clkout signal ? What are the usage scenario's of rx_pma_iqtxrx_clkout signal ? Thanks & Regards, Sach...
Deshi_Intel's avatar
Deshi_Intel
Icon for Regular Contributor rankRegular Contributor
7 years ago
Hi Sachin Jadhav, Sorry my bad. I consulted further and only find out in CDR manual lock mode, rx_is_locktoref and rx_is_locktodata is no longer indicator of CDR lock status as it was in CDR auto lock mode. In CDR Manual lock mode, these 2 signals merely just tell user CDR should operate in LTR or LTD mode only. It's will auto assert rx_is_locktoref or rx_is_locktodata signal high depend on user select it as LTR or LTD based on setting on rx_set_locktodata and rx_set_locktoref REGARDLESS of whether there is incoming data on board or not. So in CDR manual lock mode, the expectation is user needs to implement their own PPM detector logic design to compare CDR refclk with recovery clock like rx_clkout or rx_pma_clkout to decide whether CDR really lock or not. Thanks. Regards, dlim
  • SJadh1's avatar
    SJadh1
    Icon for New Contributor rankNew Contributor
    7 years ago

    Hello Dlim,

    Thank you for the confirmation.

    I have further question.

    I have connected rx_pma_iqrxtx_clkout signal to the reference input clock pin of a fPLL instance.

    I don't see fPLL getting locked ? Do you have any suggestion why fPLL is not getting locked ?

    How do I debug the reason for fPLL not getting locked.

    If I simply replace fPLL reference input clock with an on-board oscillator input then fPLL gets locked.

    Thanks & Regards,

    Sachin Jadhav