Forum Discussion

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

how to xmt 270Mb/s serial data with other data

I want to transmitter 270mb/s serial data with other data,the traditional method is :1 .recovery 270M clk from the 270Mb/s serial data .2 use the recoveried clk sample this serial data and packet them. 3 transmitter this data and other data together. 4 at receiver port ,if I must reconstruct this 270Mb/s serial data ,I need the sync clk of this serial data,then at trans port I must trans this clk recoveried from serial data. I think it's costly. Is anybody tell me how can i reconstruct this serial data without the sync clk? at receiver port ,the 270Mb/s serial data jitter must be less than 0.2UI. and I donnot want to using very expensive chip like arria or straxi.

10 Replies

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

    270Mb serial data for video? Why not to use the common algorithms used for ASI or SDI and recover the clock from stream? Or I didn't understand the problem...

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

    Clock recovery has prerequisites on the protocol and hardware side. You need a respective data coding, e.g. 8b10b and a hardware with CDR capabilities. Gigabit transceivers have it, newer Arria and Stratix hardware SERDES units have a software CDR feature. With Cyclone III and newer, clock from data recovery can be implemented using the PLL dynamic phase shift option, at least for moderate data rates. It should work at 270 MBPS.

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

    The clock recovery for 270Mbps data on Cyclone II and III is done using 337.5MHz and 337.5MHz+90deg clocks. It works in 5/4 oversampling mode.

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

    my question is not the clk recoveried from 270Mb/s serial data at transmiter. My question is that I do not want to trans sync clk with data,But I must reconstuct this 270Mb/s serial without sync clk,How???

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

    Clock is recovered at receiver, not transmitter.

    To reconstruct clock from serial data without additional clk, You have to use proper encoding scheme as I've mentioned before and recover clock from the serial stream. There are no other ways and that's why clock recovery methods were created.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    I guess, the xxyue isn't aware of the said "common algorithms" used for ASI or SDI. You can review the user manuals of the respective Altera Megafunctions to get an idea.

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

    my question is below :

    at xmt port,the 270Mb/s serial data is oversampled and made serial-parellel to 10bit parallel data,and then I transmitter it with other data,like control and ethernet . at rcv port , I must do 10bit parallel to serial process to reconstruct the original 270Mb/s serial data. but this serial data is not sync with transmitter clock.so my fifo always overflow or empty? I donot know how to do?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    SD-SDI is continuous uncompressed 270Mbps stream, while ASI is packeted stream up to 270Mbps after 8b/10b encoder. The encapsulation of both is different and You must check which one is needed.