• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 32 subscribers
  • Views 1539 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLK106L Link Pulse Polarity

g.f.
Guru 15510 points
Other Parts Discussed in Thread: TLK106L, TLK106

Hi,

I have a question about TLK106L polarity.

In customer board, output of link pulse was inverse polarity signal(TD+/TD-).

(They checked the signal from RJ45)

The customer are using default setting of Control Register3(CR3) bit[6] Polarity Swap which is 0( Normal polarity ).

So, they were thinking that link pulse will be normal polarity.

In this statement, link and communication is availabe but sometimes it won't link.

But when modified the cable by exchanging TD+ and TD-, it will link 100%.

Q1. Does TLK106L output inversed polarity link pulse by default?

Q2. If answer of Q1 is yes, is there a way to output normal polarity? (It seem CR3 bit[6] settings have no effect against link pulse polarity)

best regards,

g.f.

  • 0
    TI__Mastermind 19780 points
    Hi g.f.,

    Is the customer using 10BASE or 100BASE modes?

    The TLK106L has link polarity detection and correction automatically built in, but 100BASE isn't dependent on link polarity.

    10BASE would have issues with link polarity. If you are in 10BASE, you can read bit 4 of register 0x1A to see if an inverted polarity has been detected.

    Best Regards,
  • 0 in reply to Rob Rodrigues
    Guru 15510 points
    Hi Rob,

    Thank you for the reply.

    I will ask to my customer which mode they are using.

    By the way, I want to know the link polarity of link pulse which TLK106L outputs(question#1).

    And I have another following question from my customer.
    Q3.
    If link polarity doesn't meet with PHY of other side,
    is it available to be LINK OK and does it communicate successfully between TLK106L and other side PHY?
    Because as I previously said that sometime it wii be link ok and communicate successfully
    but sometimes it won't be link ok and doesn't communicate.

    best regards,
    g.f.
  • 0 in reply to Rob Rodrigues
    Guru 15510 points
    Hi Rob,

    I asked to the customer about 10BASE and 100BASE.
    They are using 100BASE mode. So, it doesn't dependent on Link polarity, right?

    By the way, is this "100BASE isn't dependent on link polarity" spcecified in IEEE Standard?
    And does IEEE standard requiring positive polarity for 10Base ?

    best regards,
    g.f.
  • 0 in reply to g.f.
    TI__Mastermind 19780 points

    g.f. you are correct, 100BASE-TX doesn't depend on link polarity.

    The IEEE 802.3 standard doesn't specify that 100BASE-TX should not rely on link polarity.  It does specify that the line code used for 100BASE-TX is MLT-3.  MLT-3 uses signal level transitions to indicate data instead of the signal level.  For example, if you'd like to transmit a digital 1 using MLT-3, you'd change your signal value from -1 to 0 or 1 to 0.  So in this way, no matter what polarity your pairs are in, MLT-3 decoding will always produce the same value independent of the polarity of a differential pair.

    This isn't true for 10BASE-T which uses a different line coding method.  The line coding method used for 10BASE-T is dependent on the value of the signal on the line.

    Best Regards,

  • 0 in reply to Rob Rodrigues
    Guru 15510 points
    Hi Rob,

    Thank you for the reply.
    I understood.

    Sorry, but I have one more question.

    In case of 10BASE-T, polarity need to match with the other side PHY, is it correct?
    Is this polarity need to be positve polarity?

    TLK106 outputs negative polarity signal for default so that if other side PHY have no auto polarity detection and correction,
    does setting the Control Register 3 bit[6] of TLK106 to '1'(Inverted Polarity) will be the solution?

    best regards,
    g.f.
  • 0 in reply to g.f.
    TI__Mastermind 19780 points

    g.f.

    Because the TLK106L automatically changes polarity, it doesn't matter how you set bit[6] of Control Register 3.  If you set it to inverted, and TLK detects the other PHY is non-inverted, the TLK will automatically change polarity to correct the mismatch.  Bit[6] will remain set, but the polarity will be corrected automatically anyways.

    Since the correction happens automatically, it doesn't matter if the other PHY is capable of the same detection and correction(tho most are).

    Best Regards,