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Original question:

DS90UB914A-Q1: I2C communication is failing from Serializer

DS90UB914A-Q1: Not getting correct frequency on proxy master.

Sagar Kanade
Intellectual 580 points
Part Number: DS90UB914A-Q1


Hello sir,

I have some issue regarding the frequency on I2C proxy master which serializer in my case. As shown in the image if the High time and Low time register is set with 0x82, then proxy master frequency should be 77KHz, but in my case it is not getting correct frequency. It is showing frequency beyond 300KHz. And host I2C frequency is 400KHz.

 

BR,

Sagar

  • 0
    Intellectual 580 points

    Hi Sir,

    How can I reduce BCC delay to min value 12us. By checking different value it is not going below 20us.

    BR,

    Sagar 

  • 0 in reply to Sagar Kanade
    TI__Guru** 103215 points

    Hello Sagar,

    When you say "host" which side do you mean? 914A or 913A? 

    For the BCC delay is a "fixed" value since the device needs to serialize the data and send across the link and then deserialize which adds delay. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Intellectual 580 points

    Hi Casey,

    This is the architecture. You can see the data flow from IUC to SDF. Flow is like Host_controller(IUC)-> Des -> Ser-> I2C-SPI bridge-> SDF. 

    BCC delay is fixed means this delay is able to configure or it will vary based on the frequency? As per the document, we need BCC delay 12us. But by changing the frequencies, it is not possible to get required time. 

    BR,

    Sagar 

  • 0 in reply to Sagar Kanade
    Intellectual 580 points

    Hello Casey,

    For host frequency 350KHz, what should be the proxy master(Serializer in this case) frequency. What should be the values to be places in High time and Low time register in Serializer to work its max speed i.e. 400kbps? 

    BR,

    Sagar

  • 0 in reply to Sagar Kanade
    TI__Genius 11340 points

    Hi Sagar,

    The BCC delay is based on the back channel frequency and can vary from part to part. There's not a way to change it in the registers. In the app note the I2C latency doesn’t take into account for the back channel frequency variation. The delay of 12us comes from 1 / (2.5MHz back channel / 30bit back channel sequence), and 24us is twice the typical delay because sometimes the I2C transaction is sent over two frames. The back channel can vary between 1.65MHz - 2.75MHz (2.5MHz is the nominal).

    Try setting the SCL high/low time to 0x32. Since the SCL rate has around 25% variation, you should try to adjust the register settings based on the rate you measured.

    Jiashow