• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 4 answers
  • Subscribers 35 subscribers
  • Views 1061 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

DS90UB948-Q1: Multiple I2C devices need and 1x lane SerDes capabilities

TISL
Expert 4680 points
Part Number: DS90UB948-Q1

Dear E2E Support,

My customer intend to use our DS90UB948/9 Ser-Des solutions, as shown in the bloc diagram below:

- could you confirm that it's possible to connect multiple devices on the I2C bus (behind the Deserializer)?

- what is the effective I2C bandwidth regarding the whole serial interface?

- could you confirm that the following configuration is supported with a 1-lane interface using a coaxial cable, knowing that it should support video of 1280x800, with a pclk=71.1MHz (60fps)?

 

 Regards,

  • 0
    TI__Genius 11340 points
    Hi TISL,

    -Are TP and Device in your diagram masters or slaves? If they are masters, you need to make sure the two masters can arbitrate between themselves, or you can consider using an I2C switch. If they are slaves, then it should be fine, just make sure you have the right pull-up resistors.

    -I'm not sure what exactly you are asking, but we support I2C with 1Mbps fast-mode plus

    -With a 948/949 system, the FPD-Link operates at up to 3.36Gbps line rate in 1-lane mode. Your display should work.

    Best,
    Jiashow
  • 0 in reply to Jiashow Ho
    TI__Expert 4680 points
    Hi Jiashow,

    - TP and Devices are slaves, in fact. CPU1 is the Master. So it's fine, right?
    - Regarding the line rate in 1-lane mode. I can't find any collateral that would help to understand how to compute the needed speed of our application. Is it just limited by the PCLK? Could you show us any formula or way to confirm the application viability? Is there any restriction using a coax cable?

    Regards,
  • 0 in reply to TISL
    TI__Mastermind 30515 points
    1. yes, it can support. you can refer to the app. note " ", generally FPD-Link can support up to 8 remote slave I2C device.
    www.ti.com/.../litabsmultiplefilelist.tsp

    2. it has no bandwidth concept here. it is dependent on the I2C speed which is listed in FPD-Link d/s, such as fast I2C speed 400Kbps.

    best regards,
    Steven
  • 0 in reply to Steven(Shenzhen) Shi
    TI__Expert 4680 points

    Thank you.

    I'm still confused on the 1-lane capabilities.

    Your first comment was:

    -With a 948/949 system, the FPD-Link operates at up to 3.36Gbps line rate in 1-lane mode. Your display should work.

    My question here, is not related to the I²C, but to the Serdes capabilities, to support the 1280x800 video:

    -I can't find any collateral that would help to understand how to compute the needed speed of our application. Is it just limited by the PCLK? Could you show us any formula or way to confirm the application viability? Is there any restriction using a coax cable?

    Regards,

  • 0 in reply to TISL
    TI__Mastermind 30515 points
    got it.
    FPD-Link is one serdes, the core is line rate. its application is for video transmission, so pixel clock freq. is used to assess the FPD-Link capability. in general, the video is defined by pixel clock, calculated by 1280x800x frame rate (not mentioned by you) x ~1.1blanking. if the frame rate (typ.) is 60fps, the pixel clock is ~70MHz which is less than maximum pixel clock 96MHz for UB94x single lane application.

    best regards,
    Steven
  • 0 in reply to Steven(Shenzhen) Shi
    Prodigy 50 points

    As sais in another topic, related to this one, our set up seems to work properly, finally.

    Some additional questions/remarks:

    - there is a table dealing with the bit rate and net bit rate of the I2C bus between Serializer and Deserializer on the Application Note 2173 SNLA131. (Table 1: Typical Achievable Bitrates). Could we get the same datas with the pair DS90UB948 and DS90UB949 ? In addition, how do we calculate FC & BCC delays ?

    In our configuration, the Back Channel is set at 5Mbit/sec and the pixclk is set to 71MHz approx.

    - by setting both Remote and Local rates at 400kbit/sec, does the bit rate change when setting the back channel bit rate to 5M, 10M or 20Mbit/sec ?

    Thanks in advance,

  • 0 in reply to stephane chami
    TI__Mastermind 30515 points
    Hi Chami,
    1. when BC rate is set as 5Mbps, UB94x shares the same I2C rate and delay spec. with UB925/6 as the BC line rate is similar.
    2. the delay is impacted by back channel rate but I2C rate can be support at any back channel rate cases.

    best regards,
    Steven