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Slow response to external programming

Question asked by tkloyd on May 28, 2010
Latest reply on Jun 2, 2010 by WormholeX

     We have an AD9852 PCBZ in the lab which is being programmed externally through the CS, I/O Reset, A0, and A2 lines.  The problem is that the DDS output (after having been programmed once) is responding extremely slowly to the next programmed value.  For example, if I have the DDS running at 20 MHz and I send the commands to change to 30 MHz, it takes anywhere from 5-20 seconds for the output frequency to actually change.

 

Now, I know the programming is working because the output values are correct.  I know the delay is not happening before the DDS, I see the correct data on a scope as I send it.  And I also know that this didn't used to happen (it was working ~ 1 month ago), but now the same thing happens on three different DDS boards.  I have two independent ways to program the board, both of which work.

 

What is going on?

 

Thanks,

 

Thomas

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