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75DP130 sink configuration

HE BO
Prodigy 40 points
Other Parts Discussed in Thread: SN75DP130

Hi Team,

As SN75DP130 application note mention, in a sink application, it is better to set DP130 and not to work in a default mode. my question is below.

1. when link trainning is disable and I2C control is enable, if need to set output VOD and Pre-emphasis first, then set up input Equalize? The PE level define the max

Equalize dB for each lane?

2. in order to get the best eye result, how to define output VOD and Pre-emphasis level in sink appliction when link trainning disable? It is decided by trace length

from DP130 to FPGA?

3.  I meet the case that when set input Equalize dB first, then set up output VOD and Pre-emphasis, the chip will swithc off.  Is it normal?

4. for DP130 output eye result, if the eye height is improved but in sacrifice of eye width?

5. what is the meaning of the yellow words? if it mean when I2C control enable and link trainning disalbe, Pre-emphasis should be L1?

5. 

  • 0
    TI__Mastermind 23815 points

    Hi He Bo,

    These are my comments to your questions:

    1.  VOD and PE defines the characteristics of output signal, while EQ just equalizes at input. You have to choose EQ for each line. Please follow the configuration order suggested in application note.

    2. This depends on trace length from DP130 to sink device.

    3. Pleas follow configuration order suggested in application note. Could you please provide more details about this failure?

    4. This shouldn't happen, DP130 passes test compliance for all VOD levels.

    5. What yellow words do you refer to?

    Regards

  • 0 in reply to Moises Garcia
    Prodigy 40 points

    Hi Moises,

    I would like explain detail as below.

    as DP130SS sink application note, in my sink application, I set up DP130 by I2C bus.

    1. Disable link trainning and enable I2C control;

    2. Set up input Equalize lane by lane.

        preliminarily, i set up 6dB Equalize for all 4 input lanes.

    3. Set up output VOD and Pre-emphasis level by writing DPCD register.

       firstly, set VOD level 1 and PE level 0, but eye diagram is not good enough as i expect.

      then i keep VOD level 1 and set PE levle from level 0 to level 1, then level2, then levle 3

      when PE level 3 is set up, DP130 is switch off ang no output.

      is it a normal phenomenon? and the setting sequence is meet?

    so i want to know

    1.  if I should set output VOD and PE first then set input equalize later in a sink application?

    2. if question 1 is yes, if the max Equalize is limited when VOD and PE is defined?

    3. and for VOD and PE, if they are not independed? for example, if VOD=level 1, PE can't be set up to level 3?

     4. if question 3 is yes, which one should be set firstly? and what's the criterion to set?

    thanks

    Richard

  • 0 in reply to HE BO
    TI__Mastermind 23815 points

    Hi He Bo,

    I see what is the problem, you can't have VOD L1 with PE L3.

    You can see this in datasheet, table 4, reg 103h, there is this note:
    Note: the following combinations are not allowed for bits [1:0]/[4:3]: 01/11, 10/10,
    10/11, 11/01, 11/10, 11/11; setting to any of these invalid combinations disables
    all Main Link lanes until the register value is changed back to a valid entry.

    That's why outputs disable when selecting VOD L1 with PE L3.

    The combinations that are not allowed come from DP specification.

     

    Regards

     

  • 0 in reply to Moises Garcia
    Prodigy 40 points

    Hi Moises,

    Thanks for your explantation. it is part of answer of questions.

    in 2015 datasheet tabel 3, the last two rows decribes that

    AEQ(L1) = 0dB at 2.7GHz   and then    default AEQ(L1) EQ setting at 6dB at 2.7GHz

    is it confict?

    and what is the meaning of "EQ fully programmable by EQ(L1) levels"?

    how about the other VOD level?

    Richard

    Barco

  • 0 in reply to HE BO
    TI__Mastermind 23815 points

    Hi He Bo,

    I need to check this seams to be conflict between AEQ(L1) = 0dB at 2.7GHz   and default AEQ(L1) EQ setting at 6dB at 2.7GHz

    EQ fully programmable by EQ(L1) levels means  you need to write register AEQ_L1_LANEx_SET to configure EQ, it doesn't matter what PE value you choose. EQ value is indifferent to the value of VOD.

    Regards