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AFE7444EVM: AFE7444EVM NCO Switching

Prodigy 190 points

Replies: 10

Views: 258

Part Number: AFE7444EVM

Hi

 

I  configure the NCO1 of DAC1.

 

I performed all steps as per Ti app note SLAA870.

 

I am changing the frequency from 10MHz to 100MHz. I capture that on the time domain.

 

I see an issue in the translation. I am attaching the Picture for reference. Please let me know why this issue is happening.

 

Please let me know if you need any other information. At this point, I am using AFE GUI only to switch frequencies.

 

 

With regards,

  • Hi Ganesh,

    Are you changing frequency of NCO being used or updating unused NCO and then switching to it?

    Regards,

    Vijay

  • In reply to Vijayendra Varma Siddamsetty:

    Hi Vijay,

    As I specified before I am using only one NCO1 of DAC1. Not other. this should be Phase Continuous as specified in the datasheet.

    But as you can see it's not. This behavior is random also.

    I am again repeating only 1 NCO I am using. 

    With Regards,

    Ganesh Singh

  • In reply to ganesh singh1:

    Hi Vijay,

    If you have any other setup or config file to verify other than SLAA870., you can send it across I will test that and let you know the result.

    Hope this Helps.

    With regards,

    Ganesh Singh

  • In reply to ganesh singh1:

    Hi Ganesh Singh,

    When you say "This behavior is random", is it phase continuous some times and showing this issue some other times?

    Are you using "TX NCO Update" button in the GUI to update NCO value? This uses SPI reset to reset NCO value. The programmed frequency is reflected at the transmitter output only after the newly programmed NCO is reset. NCO reset can occur through SPI or SYSREF. We can try using SYSREF signal to reset NCO and check phase continuity. This is shown in Figure 15 in the app note. 

    Regards,

    Vijay

  • In reply to Vijayendra Varma Siddamsetty:

    Hi Vijay,

    Yes exactly sometimes it's Phase continuous and sometimes it's not. as shown in the figure.

    Yes, I am trying with " TX NCO Update" button in GUI as specified in the APP note. 

    Ok will do with SYSREF also and let you know the result.

    But my question is is SPI reset of NCO can bring the phase error.? have you or any customer also observe this issue? 

    Please let us know so we can design s efficient system on this.

    With regrads,

    Ganesh Singh

  • In reply to ganesh singh1:

    Hi ,

    I took again reading.

    I run the following  script 

    AFE76xx_GLOBAL
    W 0x0010 0x55
    W 0x0048 0xf6 \\ frequency is 10.00 MHz
    W 0x0049 0x12
    W 0x004a 0x4a
    W 0x004b 0x
    W 0x0055 0x00
    W 0x0055 0x01
    W 0x0055 0x00
    Delay_ns(10000000)
    W 0x0048 0xf6 \\ frequency is 10.00 MHz
    W 0x0049 0x12
    W 0x004a 0x4a
    W 0x004b 0x
    W 0x0055 0x00
    W 0x0055 0x01
    W 0x0055 0x00
    Delay_ns(10000000)
    W 0x0010 0x55
    W 0x0048 0xa1 \\ frequency is 100.00 MHz
    W 0x0049 0xbd
    W 0x004a 0xe4
    W 0x004b 0x 2
    W 0x0055 0x00
    W 0x0055 0x01
    W 0x0055 0x00

    I am catching the transaction from 10 MHz to 100 MHz. 

    I found a similar result.

    Please let me know the correct configuration of SYSREF if i am wrong.

    With Regards,

    Ganesh 

  • In reply to ganesh singh1:

    Hi Vijay and Ti support team,

    Please let me know the status of the query.

    We are just stuck with our development.

    With regards,

    Ganesh

  • In reply to ganesh singh1:

    Hi Ganesh,

    Sorry for the delay in my response. This took time as I had to setup this in lab and debug. 

    I was able to reproduce the issue you saw on my bench. The issue was spi_sync is being routed to both MIXER and NCO. Giving SYNC to NCO results in phase reset. So we have to update the SYNC_SEL such that spi_sync is routed only to MIXER block and not to NCO. 

    Add below writes to config file to update the SYNC_SEL settings:

    AFE76xx_GLOBAL
    W 0x0010 0x55
    W 0x0051 0x88
    W 0x0052 0x22
    W 0x0010 0x55

    Regards,

    Vijay

  • In reply to Vijayendra Varma Siddamsetty:

    Thanks, Vijay,

    Can you also tell me Sysref Configuration for the same operation?

    With Regards,

    Ganesh 

  • In reply to ganesh singh1:

    Hi Ganesh,

    To use SYSREF to trigger, use below config:

    AFE76xx_GLOBAL
    W 0x0010 0x55 //Broadcast to all DUC pages 
    W 0x0051 0x22 //Use SYSREF as SYNC for frequency update 
    W 0x0052 0x11 //Phase reset disabled
    W 0x0010 0x00 // close page

    W 0x11 0x8 
    W 0x1a0 0xfc //Ungate SYSREF signal in AFE 
    W 0x11 0x0

    LMK04828
    W 0x0139 0x02 //LMK Pulsed SYSREF mode
    W 0x0143 0x13 //SPI triggered SYSREF 

    When AFE Tx NCO frequency word is updated, to send a SYSREF pulse, use below LMK write:

    LMK04828
    W 0x013E 0x00

    Also in my last reply, I sent config for SPI based SYNC (spi_sync). There's a mistake in that config. Pages are not closed at the end. Please use below config instead:

    AFE76xx_GLOBAL
    W 0x0010 0x55 //Broadcast to all DUC pages 
    W 0x0051 0x88 //Use SPISYNC for frequency update 
    W 0x0052 0x11 //Phase reset disabled
    W 0x0010 0x00 // close page

    Regards,

    Vijay