• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 6 answers
  • Subscribers 22 subscribers
  • Views 1191 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2594: Read-Back Registers

Go Bravos
Expert 6090 points
Part Number: LMX2594


Hi,

I have been using the read-back registers to observe the results of VCO calibration.  In all cases so far, read-back values rb_VCO_DACISET have consistently been 170.  Is that to be expected?

 Secondly, values for VCO_SEL, VCO_CAPCTL, and VCO_DACISET in registers r20, r19, and r16 do not change as I have the VCO calibrate in different VCO bands.  Is that to be expected because I am not forcing calibration values?  Should I therefore use rb_ VCO_SEL, rb_CAPCTL, and rb_ VCO_DACISET to build a calibration table that will be used to force values later for speed-up?

Thanks.

  • 0
    TI__Guru** 110790 points
    Hi Bravos,

    Did you enable the MUXout pin to be register readback output?
    Set MUXOUT_LD_SEL=0 to enable readback output.
    When you program the device to read back, make sure the MSB is 1.
  • 0 in reply to Noel Fung
    TI__Expert 6090 points
    Hi Noel,
    I am using TICS Pro to control the evaluation board and to read back registers. MUXout is set to Readback. I presume TICS Pro handles the MSB correctly.

    Rb_VCO_SEL and rb_VCO_CAPCTRL are updating and Rb_VCO_SEL indicates the correct VCO # that I would expect for the operating frequency. Lock Detect rb_LD_VTUNE says Locked.

    It’s only rb_VCO_DACISET that I question because it always reads back “170” although I have tried calibrations at high, mid, and low ends of all VCOs.

    Please let me know your thoughts.
    Thank you.
  • 0 in reply to Go Bravos
    TI__Mastermind 28021 points

    Hi,

    As a sanity check, try disconnecting the ribbon cable from TICSPro and then you can be sure that you are actually reading the part for rb_VCO_DACISET.

    The other thing you might check is on the bits/pins tab that the "VCO_DACISET_FORCE" bit is not checked under the VCO group for IDAC.

    Regards,
    Dean

  • 0 in reply to Dean Banerjee
    Prodigy 20 points
    I tried both of Dean suggestions but still consistently receive a readback value of 170 for DACISET.

    Disconnecting the ribbon cable did read back "0" for all readback registers, including DACISET. Re-connecting the cable restored the DACISET reading to 170. VCO_DACISET_FORCE bit is not checked in TICSPro. Interestingly, the readback was still 170 after checking the VCO_DACISET_FORCE bit with a value for DACISET different from 170.

    Other ideas to test this are welcome.

    Regards
  • 0 in reply to Edward Hall
    TI__Mastermind 28021 points
    Edward,

    This does defy reality to me. One thing to be sure of is that when you forced the value, you are programming VCO_DACISET, not VCO_DACISET_STRT.

    Cycle power.
    Go to "Default Configuration" in the menu and load the default mode.
    Toggle the RESET bit (set to 1 then set to zero)
    Press Ctrl+L on TICSPro
    Change the MUXOUT_SEL to show "Readback"

    Regards,
    Dean
  • 0 in reply to Dean Banerjee
    Prodigy 20 points
    Thank you to all who answered. Dean's reset steps cleared the issue for me. I now see the variations in rb_VCO_DACISET that I expected.

    Regards,
    Edward
  • 0 in reply to Edward Hall
    TI__Mastermind 28021 points

    Edward,

    Glad this is resolved.  I will close this thread.

    Regards,

    Dean