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Altera_Forum's avatar
Altera_Forum
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15 years ago

rx_freqlocked signal on Cyclone IV GX

I'm seeing strange behavior from the rx_freqlocked signal that's output from the Cyclone IV transceiver block in basic mode.

According to the transceiver documentation:

--- Quote Start ---

In automatic lock mode, the switch from LTR to LTD states is indicated by the

assertion of the rx_freqlocked signal and the switch from LTD to LTR states

indicated by the de-assertion of the rx_freqlocked signal.

--- Quote End ---

However, I'm seeing this signal asserted even when there's no data available at the receiver for the for the CDR to lock to.

Clearly I'm not understanding exactly what this signal is telling me. Does anyone have some insight on this?

Thanks

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  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    hi,

    i had met the same problem, i used the quartus11.1, but the rx_freqlocked is struck

    assert. i have no idea, do you have any suggestion about it ?

    thanks a lot!!
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    Sorry for the delayed response, I haven't been checking here recently.

    As far as I can tell, the rx_freqlocked signal is simply broken. I'd love to hear otherwise, but no one that's posted here has ever reported getting it to work.

    I had a support request in to Altera for 8 months and my impression was that they never even really tried to reproduce the problem. I finally let the support request expire out of frustration.

    If anyone ever gets this to work, please post here and let us know. For now though I'd recommend just working around it.