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LMX2820: Why I can not read LMX2820

Wei Zhao
Prodigy 30 points
Part Number: LMX2820

Hi,

I have four LMX2820 synthesiezer on my board. I used four CE signal and four CS# signal for each of LMX2820. and I used just one SDI signal and one MUXOUT signal to control all of them.

For example, I selecte one synthesizer by enable the related CE signal and CS# signal,  then sent the SDI signal to programming it. it works good for SDI signal. the reg value on the GUI looks programmed and I can see the output looks right as I want.  However, when I want to readback the register information by by click the "read resgiter" on the GUI, I will see the register became to 0. I checked the MUXOUT pin on the LMX2820, the waveform looks good to me. Could you let me know why I can not read the register value?

Thanks,

Wei

  • 0
    TI__Mastermind 28011 points

    Wei,

    A few things to be aware of:

    1. You can still program the device if it is powered down if CS# is low

    2. The MUXout pin does go tri-state when you power down the device, but on our EVM, board, the CE pin is tied high.  So ensure that the MUXOUT pins for the other devices that you are not reading from are tri-state (high impedance)

    3.  I tried this on our EVM and it worked fine.