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Linux/DS90CF383B: TXOUT0+/- questions

mike.liu
Prodigy 70 points
Part Number: DS90CF383B

Tool/software: Linux

Test DS90CF383B output signal TXOUT+/-.There are several questions as below:

1.Why is the signal level different?

2.Why does a cycle have only 4bit data?

  • 0
    TI__Intellectual 1635 points

    Hi Mike,

    1.  The signal level is not expected to be different as you are observing on your scope.  Can you please confirm the frequency of TxCLKIN (input clock)?  Please also check your scope and probes to make sure they are rated for the data rate you are using.  Please note there will be 7 bits of data for every clock cycle. 

    2. As noted above, you should observe 7 bits of data for every clock.  Please see the figure below that I have pasted from Figure 9 of the DS90CF383B datasheet.

    Regards,
    Ryan

  • 0 in reply to Ryan Hashimoto
    Prodigy 70 points

    HI，Ryan

     The frequency of TxCLKIN (input clock) is 65MHz.

    How to investigate the problem?Any Suggestions?

  • 0 in reply to mike.liu
    TI__Intellectual 1635 points
    Hi Mike,

    What are you using to drive your TxCLKIN? Based on the photo above, the signal is not very clean. The DS90CF383B will output 7 bits of data for every clock cycle, which will put an even higher requirement on your bench capture equipment.

    Please ensure that the scope probes you are using can accommodate transmit data at 455Mbps. Based on the image above, your scope is only has 500 MHz bandwidth which can cause problems also.

    Regards,
    Ryan
  • 0 in reply to Ryan Hashimoto
    Prodigy 70 points

    Hi，Ryan

    Can you provide your e-mail?

    1.AM335X drive  TxCLKIN.

    2.txout_clk&data as below: isonly have 2 bits of data for every cycle.

  • 0 in reply to mike.liu
    TI__Intellectual 1635 points
    Hi Mike,

    My concern still remains that the bandwidth and sampling range of your scope and probes is causing the issues that you are seeing on the screen. Please confirm the ratings on these components to ensure you are using the right measurement equipment.

    You mention that you are only seeing 2 bits of data for every clock. What data are you driving into the device and what is your expected output?

    If you need to send any additional files, my email is: Ryan.Hashimoto@ti.com.

    Regards,
    Ryan