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DAC38RF82: NCO only register settings

Prodigy 110 points

Replies: 5

Views: 59

Part Number: DAC38RF82

Hi,

could someone post the DAC38RF82 NCO only register settings for this device please?

using a custom board with external clock of 9 GHz. can drive the control signals.

thanks,

joseph

  • Hi Joseph,

    To generate a tone using the NCO only you will need a couple of register settings. You will need to enable the mixer and the NCO, this is accomplished by writing 0x2620 to address 0x10C, this also changes the data format to offset bianry (Page 76 in datasheet). You can then use address's 0x11E -0x120 to set the NCO frequency (Page 83 in datasheet). Lastly you will need to write 0x1 to address 0x12F in order to set a constant input.

    If everything is configured correctly these are the registers that you would need to change in order to get a NCO only output for channel A.

    Regards,

    David Chaparro

  • In reply to David Chaparro:

    Thanks David.

    not producing any tone.

    i am

    1. setting TXENABLE pin low

    2. Reset pin low then high

    3. reading register 0x7F and verifying that it is 0x8009

    4. setting 0x9 to 1 (select page 1); also read back and verify

    5. setting 0x10C to 0x2620; also read back and verify

    6. setting registers 0x11E - 0x120 to 0x2000; also read back and verify (for a random tone)

    7. setting registers 0x130 to 0x2222; also read back and verify (some amplitude, just in case this is needed)

    8. setting registers 0x12F to 1; also read back and verify

    9. set TXENABLE pin high

    i can see that the DAC is getting clock of 9 GHz

    what is being missed?

    regards,

    joseph

  • In reply to Joseph Pathikulangara:

    Joseph,

    I was using the DAC EVM GUI to set the registers so to select the slice 1 include a 1 in the address, for example 0x11E is page 1 address 0x1E and page 2 would be 0x21E. What you can do is after selecting page 1, by writing 0x1 to address 0x9, try the register settings with the first 1 removed in the addresses. After writing those registers try syncing the NCO (with sysref or sif sync) depending on the sync mode selected. I have sif sync selected, so I write 0x332 to address 0x28 and then I write 0x330 to address 0x28.

    Regards,

    David Chaparro

  • In reply to David Chaparro:

    Hi David,

    I understand notation of address 0x11E and am doing the right sequence. that is when the page changes, write the page first and then the 7 bit address.

    also writing 0x128 0x332 flowed by 0x330 to sync

    still no signal.

    the GUI is doing something more to get the NCO going.

    what to do now?

    we need the chips perspective. stating with reset, what all needs to be done.

    or is it possible to get a trace of what GUI did from the beginning?

    thanks and regards,

    joseph

  • In reply to Joseph Pathikulangara:

    Hi David,

    I have come to this question of NCO only mode as the main task of getting the chip to produce the signal is not successful. yet.

    ultimately GUI is not a substitute for proper documentation.

    just took a chance and removed step 2 from previous post (resetting the chip). now the registers from previous programming are retained.

    and lo and behold the NCO produces signal!

    now that I know that chip is alive, on to the main task.

    is there a newer datasheet or a proper bring up guide?

    thanks and regards,

    joseph