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LMX2492: Programming as a single register

Nicholas Strong
Prodigy 90 points

Part Number: LMX2492
Other Parts Discussed in Thread: USB2ANY

Evening,

I am attempting to program the LMX2492 as a single register as your datasheet indicates should be possible.

This results in me sending 0x008d, and then 142 bytes of data over SPI while keeping the LE low during the entire write (asserting at the end). This is from an FPGA.

It is currently not programming. My question would be I notice that your TICS Pro utility often skips registers 40-57. Should I be including writing to these registers with 0x00 or does the chip actually expect only non-reserved registers to be included when programming as a single register.

Any other insight you can give? The TICS Pro software always seems to include the address and program each register individually. Is there any way to make it program the entire chip while only sending the address once?

Thank you,

Nicholas Strong

Update: I have tried to use the USB2ANY Explorer software to duplicate my design's SPI, but unfortunately the USB2ANY Explorer has maximum byte count of 53 so I cannot replicate fully programming the device. I have done a few registers at once but I haven't had a chance to play with the reserved register edges or done a large amount of register programming.

  • +1
    TI__Guru** 121350 points

    Hi Nicholas,

    Single register programming has to program all the necessary registers in order, we cannot skip some of those in the middle of the sequence, so we need to program those Reserved registers as well.

    However, not all Reserved registers' content are zero, that may be the problem you are having if you write them all to zero.

    Below shown the actual value for these registers. These are silicon default values after a Vcc power up or a soft reset, so we don't need to write these registers if we are not doing single register programming.

    Register Actual value
    R85 0
    R57 0
    R56 F
    R55 - R54 6F
    R53 F
    R52 8F
    R51 - R50 F
    R49 AF
    R48 F
    R47 4F
    R46 30
    R45 - R40 0
    R15 - R3 0
    R1 0
  • 0 in reply to Noel Fung
    Prodigy 90 points

    Hi Noel,

    That's good information, thank you!

    Can you assist me in making sure I didn't miss this information in the datasheet? I have posted the relevant page and I think your information may fall under "unless otherwise stated" but I cannot see where it was otherwise stated?

    Is there somewhere else I should have referenced for this information?

  • 0 in reply to Nicholas Strong
    TI__Guru** 121350 points

    Hi Nicholas,

    The highlighted statement may not be completely correct, we need a better presentation to the reserved registers. Apologies for the confusion.

  • 0 in reply to Noel Fung
    Prodigy 90 points

    No worries, it happens. I just wanted to make sure I wasn't missing something.

    Thank you!