AD9520-0 Communication problem.

Hi,

I am using AD9520-0 clkgen, I am trying to communicate it using SPI.

I have made the following configuration:

  1. I have kept SP0 and SP1 of AD9520 high.
  2. I have kept the pins REF_SEL,RESET,SYNC,PD high and EEPROM low.

I am not able to read any of the registers from it.

I am writing a value 0x8003 to read back the PART-ID.

Steps followed are as below;

  • Keep all the SPI lines pulled high.
  • Pull CS to low.
  • Write first byte(0x80)
  • Write address(0x04)
  • Write 0.(to read back )
  • Set CS high.

I have attached the schematics followed. I have connected 24MHz oscillator to REFIN and REFINB. But when i probe at those points i didnt see any frequency at all.

Please tell me if any other procedure need to be followed to initialize it.

Regards,

Prakash B J

AD9520.pdf
  • 0
    •  Analog Employees 
    on Dec 4, 2013 8:23 PM

    Hello Prakash,

    Answers are in-line:

    > I am using AD9520-0 clkgen, I am trying to communicate it using SPI.

    > I have made the following configuration:

    > I have kept SP0 and SP1 of AD9520 high.

    PK: That's correct.

    > I have kept the pins REF_SEL,RESET,SYNC,PD high and EEPROM low.

    PK: REF_SEL will do nothing in your config.

    PK: PDb, RESETb and SYNCb are active low, so they should be high when you program the part.

    >  I am not able to read any of the registers from it. I am writing a value 0x8003 to

    > read back the PART-ID. Steps followed are as below;

    • Keep all the SPI lines pulled high.
    • Pull CS to low.
    • Write first byte(0x80)
    • Write address(0x04)
    • Write 0.(to read back )
    • Set CS high.

    This should be correct, although writing only 0x8004 should be enough.

    After get that working, another good register to use to verify that you're writing correctly is Register 0x01A. Writing 0x30 will make the LD pin high, and writing 0x00 will make it low. It's very handy for debugging.

    > I have attached the schematics followed. I have connected 24MHz oscillator to REFIN and REFINB. But when > i probe at those points i didnt see any frequency at all.

    This is expected, as the crystal maintaining amp must be turned on first using the serial port.

    -Paul Kern

  • Hi pkern,

    Should i turn on the crystal using the serial port or the AD9520 comes with default turned on ?

    If so what are the steps to turn it on?

    I didnt find any information on this in the datasheet.

    Thanks,

    Prakash BJ

  • Hi Pkern,

    I have got the SPI working one way. I am able to toggle the LED LD. But, couldn't read back the register values.

    Thanks,

    PrakashBJ

  • 0
    •  Analog Employees 
    on Dec 6, 2013 3:08 AM

    Hi Prikash,

    > Should i turn on the crystal using the serial port or the AD9520 comes with default turned on ?

    > If so what are the steps to turn it on?

    The best way to generate register settings is to use the eval software. Use the following link to download the evaluation software and user's guide (UG-076):

    http://www.analog.com/en/clock-and-timing/clock-generation-and-distribution/ad9520-0/products/EVAL-AD9520-0/eb.html

    To answer your question, the maintaining amp is turned on by writing a "1" to Bit 6 of Register 0x01D.

    > I have got the SPI working one way. I am able to toggle the LED LD.

    > But, couldn't read back the register values.

    Check the datasheet to see a comparison between the read and write waveforms, and compare that with what you have. In your first post, it appeared that you have an extra write of 0x00 after your write.

    -Paul Kern