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DP159 - CDR Not locked after TPS1

Kyoung Sup Chang
Prodigy 180 points

Dear Team.

My customer wants to use DP159 as a redriver to use Eye Scan features in DisplayPort source.

I'm using WQFN (40 pin) package  and let opened IN_CLKP/N and IN_D2P/N signals.

I could check image successfully showing when I use DP159 as retimer in DisplayPort

But when I try to use it as a redriver I couldn't get signal locked after TPS1 (Page0x01, Offset:0x00 => returns 0x03)

I checked TPS1 signal properly showing in oscilloscope.

And heres my Initialization Sequence(pseudo code) which explained in SLLA358

RBR_HBR_HBR2_Common_Init();

Disconnect_Event();

BW_handler(); // <== for LBW_HBR and LaneCount = 2

Init_Sensor_Before_TPS1();

Execute_TPS1();

Determine PLL Locked(); // by checking Page0x01, Offset:0x00 and returns 0x03

Is there anything I can check?

Please help me to escape from this.

Thank you

Best Regards,

  • 0
    TI__Mastermind 23815 points

    Hi,

    DP159 can be configured as DP retimer, if you are looking for DP redriver you may want to take a look at DP130 or DP141 for higher data rates.

    When using DP159 as a retimer PLL will lock using the reference clock, then will create new signals with the same information.

    DP159 is not intended as a DP redriver, as a redriver you are not creating new signals just equalizing and redriving input signal, you won't use the PLL, thus, you'll never get lock.

    Regards

  • 0 in reply to Moises Garcia
    Prodigy 180 points

    Dear, Moises Garcia.

    Thank you for your reply.

    My customer wants to use this IC because of eye-scan feature.

    That's why I use this IC.

    And can you tell me the meaning of "you're not creating new signals" in detail?

    Is this mean that I couldn't get signal locked when TPS1 (TPS1 will make same clock signal)?

    Do I need to send real data if I want to get PLL locked?

    Please tell me.

    thank you.

    Best Regards,

  • 0 in reply to Kyoung Sup Chang
    TI__Mastermind 23815 points

    Hi,

    Lets summarize the difference between redriver and retimer.

    redriver:

    Input signal is equalized and retransmitted. Signal integrity issues in input signal will be cleaned, what can't be cleaned will be present in output signal.

    There is no PLL, thus, no lock signal.

    retimer:

    Clock and data is recovered, this is done using PLL, when clock is recovered you will have lock, then using this recovered clock it will recover the data.

    With this recovered data the transmitter will create a new output signals.

    Regards

  • 0 in reply to Moises Garcia
    Prodigy 180 points

    Hi,

    Thank you for your reply.

    I now understand differences clearly. thank you.

    I could check images when I use DP159 as a redriver.

    But I couldn't lock PLL when I use DP159 as a retimer. 

    I'm My current situation is still in hang stalled.

    I couldn't lock my signal yet even that I could check TPS1 signal showing properly.

    ( I could check Eye Height 280 mV which is bigger than minimum spec of 75mV )

    I want to use DP159 as a DisplayPort re-timer and also want to use Eye-Scan Features.

    I'm using two lanes. So, I put two signals D0_IN_P/N, and D1_IN_P/N and left open CLK_IN_P/N and D2_IN_P/N.

    and I'm using 40 pin package which has limitations in some functions that I don't use.

    Is there anything that I can check? 

    Please tell me.

    Thank you.

    Regards,

  • 0 in reply to Kyoung Sup Chang
    TI__Mastermind 23815 points

    Hi,

    Just to confirm we are ont he same page, you ciuld use DP159 as a redriver without problem, problem comes in retimer mode where you can't get lock, so you are no enabling Tx lanes and there is no video; besides, you are using D0 and D1 while D2 and CLK are floated.

    DP159 is intended for HDMI application so it uses HDMI naming, DP has a different naming for high speed lanes

    DP            HDMI

    LN0   ->   D2

    LN1   ->   D1

    LN2   ->   D0

    LN3   ->   CLK

    So, DP lane 0 should connect on D2 and DP lane 1 connects to D1.

    DP159 is looking for clock signal on LN0

    Regards

  • 0 in reply to Moises Garcia
    Prodigy 180 points

    Dear, Moises Garcia

    I appreciate that your wise reply.

    This is what I really want to know. Thank you very much.

    Now I understand why I couldn't get locked (Because of that I floated LN0(D2)) 

    I'll let you know after I test with new board.(I'll make a new board to test)

    Thank you.

    Best Regards.

  • 0 in reply to Moises Garcia
    Prodigy 180 points
    Thank you very much. I could successfully lock my signal with DP159 with your lane Order.
    Thank you.