how to let ad9910 output a train of  pulsed sinusodial waves

Hi, everyone.

Recently, I use a Xilinx FPGA(Spartan6-lx9tqg144) to control the ad9910. I let the AD9910 work in the DRG mode, and I got the DRG mode work, realizing the freqency sweep from 200MHz to 250MHz.

furthermore, I wanna to get the following waves, but I do not know how to make it.

Let Ti(i=1,2,3,4,5...) denote the time duration

T1 :  0-1us , AD9910 output a  200MHz sinusodial wave
T2 :  1-10us, AD9910 output none
T3 :  10-11us, AD9910 output a 200MHz sinusodial wave
T4 :  11-20us, AD9910 output none
T5 :  20-21us, AD9910 output a 202MHz sinusodial wave
T6 :  21-30us, AD9910 output none
T7 :  30-31us, AD9910 output a 202MHz sinusodial wave
T8 :  31-40us, AD9910 output none
......
The process may repeat from 200, 202, ... 249, to  250 MHz

(1) I found that, the maxium speed of the Serial Port of AD9910 is 70Mbps. that means, in 1us, 70bits are transmited at the most.
If I use the ASF Register to control the Amplitude, I should send
8+32 bits(Phase One 8bits, and Phase two 32bits) via the SPI protocol
Does it  mean that it is hard for us to update the registers in 1us?

(2) If I use the parallel data mode, Can I make it?

(3)And I found that,
If I use the ADI's AD8180(a multiplex chip, which has a 5ns channel switch time), Maybe I can control the output, but I am not so sure.

Because, I currently use the prototype board, I wanna to know How to use the AD9910 to Control the output amplitude?


Any advise are appreciated.
Thank you

JiongWU

Parents
  • It appears your desire to control amplitude amounts to simply turning the output off and on. If so, I would recommend using the manual OSK mode.

    1. Prior to starting the transmission sequence, program the ASF register to full scale (you only need to do this once).
    2. Program CFR1[23]=1 (enables OSK pin for amplitude control)

    This allows you to turn the output off and on via the OSK pin (Logic 0 and Logic 1, respectively) without having to program any registers.

    Because frequency changes occur on 20us boundaries, that should allow plenty of time to write a new frequency (32 bits) via the SPI.

    The challenge will be synchronizing the SPI operation and IO_Update with the OSK pin, but it should be doable.

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  • It appears your desire to control amplitude amounts to simply turning the output off and on. If so, I would recommend using the manual OSK mode.

    1. Prior to starting the transmission sequence, program the ASF register to full scale (you only need to do this once).
    2. Program CFR1[23]=1 (enables OSK pin for amplitude control)

    This allows you to turn the output off and on via the OSK pin (Logic 0 and Logic 1, respectively) without having to program any registers.

    Because frequency changes occur on 20us boundaries, that should allow plenty of time to write a new frequency (32 bits) via the SPI.

    The challenge will be synchronizing the SPI operation and IO_Update with the OSK pin, but it should be doable.

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