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?