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AD9524 SPI programming

Hi folk,

I'm trying to use this PLL with a PIC24 Microchip microcontroller.

The interface is an SPI because I leave the SP0,SP1 pins starting through the integrated pull-down resistors.

What is not clear, is the programming sequence. I try to be more clear about.

There is a command that's need to be sent for register update.

Have this command sent for each configuration register write?

Thank you.

Best Regards,


  • Hi,

    We refer to the register command of which you speak as an IO Update. The transfers the allows the user to control when register write take effect relative to other writes. For example: If you are writing to a divide value of 500 (0x1F4) to the RefA input divider, writing R0x10 = 0xF4, R0x11 = 0x01, R0x234 = 0x01 allows the divider to change directly to a value of 500 as opposed to the hypothetical scenario where the register writes immediately take effect (i.e. no IO Update required) which would result in the divider being programmed as 244 then 500.

    Typically, when initially programming the device, one writes all the configuration registers to the part and then issues a single IO Update to latch them in. Then the initialization sequence is written (for example calibrating the VCO and syncing the output dividers) which requires intermediate IO Updates to implement a sequence.

    For example: A manual divider sync must be executed by writing R0x232[0] = 0x01 (Set dividers into Reset), R0x234 = 0x01 (IO Update), R0x232[0] = 0x00 (Release Dividers from Reset synchronously), R0x234 = 0x01 (IO Update).

    Writing the sequence R0x232[0] = 0x01, R0x232[0] = 0x00, R0x234 = 0x01 would never actually place the dividers into Reset, so a manual sync would not occur.

  • So I can send all the commands/data and finally perform an update.

    Thank you for the answer.

    Maybe I have an hardware problem.

    Tomorrow I will try.

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    Thank you,
    EZ Admin