AD9858: Output frequency change

Document created by analog-archivist Employee on Feb 23, 2016
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Is it possible to change the output frequency by updating only the lowest bytes
(8 bit or 2x8 bit)of the 32 bit frequency register or do you have to update all
bytes even if there is no changes in the higher byte values ?
If yes, is the update rate still 100 MHz ? How long does loading to the
frequency register take ?

 

Yes, they can change any one of the 4 bytes in the frequency tuning word, or
they can change and update all 4. The update rate would be 100MHz, as that is
the maximum parallel write speed. If they were writing all 4 bytes, the maximum
update rate would be 25MHz. Loading to the frequency register will occur at the
next rising edge of sync-clk, followed by the pipeline latency, at which time
they will see the frequency change in their output.

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