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AD9911: FTW register update

Question asked by luca.banchi on Apr 26, 2017
Latest reply on Apr 26, 2017 by JLKeip

Dear Support,


I will adopt the AD9911 in my design. I want to know how many registers (and how many bits) I have to update on the device in order to change the working frequency in the range 191.477MHz to 196.022MHz. In particular, the updating time is my concern. For what I got form the datasheet, it is sufficient to update ONLY the register number 4 (0x004) with the new FTW coded on 32 bits, am I right?

This results in: 5ns x 32bits = 160ns for the payload (DATA).

On page 34 it seems that the register is addressed by using 8bits (INSTRUCTION BITS), and the data is transmitted over 8bits (DATA BITS), the question is: is it necessary to transmit the instruction bits every 8 DATA bits?

This is in order to establish the total transmission time required to update frequency.


Regarding the I/O UPDATE command, I which is the relation with the I/O UPDATE signal and the register update?


Thank you in advance for your support,

Luca Banchi