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LMX2615EVM-CVAL: LMX2615 eval board register readback issue

Robert Wedeen
Prodigy 10 points
Part Number: LMX2615EVM-CVAL
Other Parts Discussed in Thread: LMX2615-SP

We are using the LMX2615-SP on the CVAL evaluation board as procured from TI and a description of the issue is outlined below.

 

 

 

Objective:

 

For our application, we would like to be able to read values from the registers in the LMX2615-SP RF synthesizer. The goal is to do an initial write to the registers and then, from that point on, continually read back the values from all the registers and look for any changes that might occur due to upsets from the space environment. We will eventually use our own software to do this.

 

 

 

Issue:

 

After writing to the registers or even just one of the registers, we try to read the values back using TICS Pro and get “FFFF” in each case. We have also tried this with out own software and get the same result of “FFFF” for each readback.

 

 

 

Request:

 

Please educate us on how we can read the correct values from the registers or prevent them from becoming corrupted if that is happening.

 

 

 

Please advise.

 

 

 

Thank you

 

Bob

  • 0
    TI__Guru* 95850 points

    Hi Bob,

    Did you set the MUXOUT pin to readback output?

  • 0
    Prodigy 10 points

    Noel,

    Thank you that was very helpful and now we are able to read the registers.

    What we are now observing is that, within several minutes after loading a TICS Pro file, some of the register values change on their own. For example, registers 60 and 112 had a bit change randomly on occasion and we're not sure what would cause that. So far there has been no impact to the output signal, but we will be looking for bit changes related to upsets and do not want to have any false alarms. Are there any registers that would be expected to update on their own? If there are only a few then perhaps we could ignore them.

    Please advise.

    Thank you.

  • 0 in reply to Robert Wedeen
    TI__Guru* 95850 points

    Hi Robert,

    R60 is LD_DLY, which I don't believe its value will change over time. 

    R112 is rb_VCO_DACISET+ some hidden registers, unless you did another VCO calibration, otherwise rb_VCO_DACISET should not change over time. 

    Both of these registers will not affect RF performance. However, if LD_DLY did change, it may affect VCO lock detect time.