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Register does not work to set CMLOUT on DS90UB928Q eval board

Rutger Smink
Prodigy 30 points
Other Parts Discussed in Thread: ALP, DS90UB928Q

Hi all, we are having trouble to visualize the eye-diagram on our DS90UB727Q to DS90UB928Q FPD-link III employing the evaluation boards. It is mentioned that at the Rx side we need to Enable the CMLout pin through the register (0x56). However, this address is reserved in the ALP gui and can not be set to '1' to Enable. The link is CDR locked and serializer and deserializer are linked as well. Thus how to set the enable on the CMLOUT?

Thanks, Rutger

  • 0
    Prodigy 30 points
    Maybe I am misreading the register and although the default is disable, on the EVM the register is already set to 0x00. I see no boxes checked in the gui. Still there is nothing to be seen on the CML pins when hooked up to a scope. We do have a lock.
  • 0 in reply to Rutger Smink
    TI__Genius 14015 points
    Hi Rutger,

    It sounds like there may be an issue with the Registers tab of the ALP GUI. Can you try using the Scripting tab instead? Here are some example commands:

    hex(board.devAddr) \\this will return the device ID that ALP is talking to. It should match the 928 address.
    board.devAddr = 0x58 \\this will set the device ID
    hex(board.ReadReg(0x00)) \\this will read offset 0x00. It should return the expected address if I2C is working properly
    hex(board.ReadReg(0x56) \\this reads offset 0x56 to see whether CMLOUT is enabled.
    board.WriteReg(0x56, 0x00) \\this writes to offset 0x56 to enable CMLOUT.

    Thanks,
    Jason
  • 0 in reply to Jason Blackman
    Prodigy 30 points

    Thanks Jason, for your reply.

    You were correct. It is indeed an issue with the register tab. Last week, we used the I2C communication pins to set the 0x56 register and enable the CMLOUT successfully. Now seeing your "scripting" code, that would have been a lot faster than setting up the I2C bus I guess. We were able to see an eye-diagram by using one of the CMLOUT pins as a trigger for the scope. We tried the CLK and MCLK pins at the 928 DES as well for triggering though without success. Maybe there is another means of triggering (read in another post that one should use the PCLK, though we don't see that output on the 927/928 EVMs...we will check the CLKOUT instead).

    Thanks again, much appreciated,

    Rutger