AD9914 direct mode

Now, I use FPGA to control AD9914 to generator the frequency which I set. But I met a problem that when the frequency output , then if I set the 32-bits as 0, and no pulse of IO_Update, there is no output. Following  is my configuration(Completely controled by FPGA): (Port streaming enbale = 0 so need a IO_Update pulse ) 

1. Disabled USB enbale;

2. Provide appropriate REF CLK;

3. F[3:0] = 0010 (direct mode for 32-bits FTW);

4. Output FTW by FPGA;

5. Output IO_UPdate pulse by FPGA;

6. The output frequency is correct;

7. Output FTW = 0 through FPGA;

8. Can't get any output, no signal detected by oscilloscope;

9. In step 7, if FTW !=0, the output is still right。

My questions are:

1. In datasheet, if want to change ouput besides FTW, IO_Update also needed, but, I set FTW = 0, no IO_Update pulse, the output turned 0;

2. If the FTW != 0, no IO_Update pulse, output can not be changed .

  • 0
    •  Analog Employees 
    on May 7, 2021 3:00 AM

    Hi,

    The data sheet indicates that when the parallel port streaming enable (0x00[17]) is set to Logic 1, the parallel port operates without the need for an I/O_Update. When this bit is Logic 0, the device delivers the parallel port data to the appropriate registers but not to the DDS core. Data does not transfer to the DDS core until I/O_Update is asserted. With this, kindly try to set port streaming enable to 1 and observer the behavior of the output.

    Best regards,

    Mark