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Altera_Forum's avatar
Altera_Forum
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13 years ago

Using PLL to synchronize Data stream on Cyclone III

Hi everyone,

I have a 125MHz asynchronus NRZI bit-stream as an input into my FPGA. I want to sample this bit-stream and make sure, that I sample each bit once and correct. Can I use the NRZI bit stream as the reference-input to a PLL to phase-allign the generated clock to the data and then sample it with a Flip Flop on the falling edge?

Thank you very much for your help

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

    No. As long as can't derive a continuous square wave from the input signal, a regular FPGA PLL won't work. The PLL dynamic phase shift feature can be utilized to make a software CDR with limited frequency range, well sufficient for a data stream with crystal timed frequency.