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AFE7950EVM: Regarding changing nco frequency by SPI

AK
Prodigy 250 points
Part Number: AFE7950EVM


For programming the the NCO frequency, 16 bit frequency word can be programmed via SPI. I want to know the time after which ti will reflect, and the constraints it puts on the maximum hopping rate from one frequency to another. 

  • 0
    TI__Mastermind 18001 points

    Hi AK,

    To program the NCO through SPI there are a series of register writes that must be performed, see sequence below. This means that when switching by SPI you will be limited by the amount of time it takes to perform the SPI writes mentioned below. One thing to note is that if your application allows you to know the next frequency ahead of time then you can load the 32 bit word and wait to toggle the NCO load bit till it is required.

    1. Open the Rx/Tx Dig Page (1 SPI write)

    2. Write the 32 bit word (4 SPI writes)

    3. Set the NCO load bit to 1 (1 SPI write) [NCO is loaded only when this bit is toggled from 0 to 1]

    4. Set the NCO load bit to 0 (1 SPI write) [Toggle bit back to 0 for next NCO load]

    4. Close the Rx/Tx Dig Page. 

    Regards,

    David Chaparro