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Altera_Forum's avatar
Altera_Forum
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17 years ago

phase alignment in SERDES

I'm using Cyclone III altlvds_tx and I have a problem about setting phase alignment of 'tx_outclock' with respect to 'tx_out'.

There is 4 channels and the deserializtion factor is 7. I expect the phase alignment like this:

---|____|------|____|--- ... tx_outclock

0 1 2 3 4 5 6 0 1 2 3 4 5 6 ... tx_out

It seems that i should set phase alignment to 720 degrees. But the list box provide only 0~360 degrees.

can any one help me?:confused:

2 Replies

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

    To my opinion, in case of the Cyclone soft LVDS, the meaning of some MegaWizard and MegaFunction parameters isn't as clear as it could be. The reason for this fact is mainly in the complex ways, these IP is implemented. In some cases, you can set other parameters when instantiating the MegaFunction manually. But you should always check the results, e.g. by Quartus Simulator.

    Because Cyclone LVDS MegaFunctions are basically made from DDIO cells, a PLL and some registers, it's can be straigthforward, to implement the respective function by yourself. This is necessary anyway in some cases, e.g. if you need larger deserialization factors than provided by the MegaFunction.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    Thank you for your reply.

    I will try to edit the parametes manually and see if it works.