Questions regarding AD9102 Trigger signal

Question

Customer questions regarding the AD9102 trigger 
 The customer likes the TRIGGER signal as a means of stopping and starting DAC output. 
 Questions: 
 1) If he use the DDS circuitry exclusively to feed the DAC, is it possible to use the TRIGGER signal as a means of starting and stopping the output from the DAC? Does he need to load the SRAM with 1s to do this? 
 2) If the TRIGGER can't be used this way, how does he control the start of DDS output from the DAC? The start of the DDS waveform needs to be sync'd with an external reference in my application. 
 3) How does the DDS_PHASE value get combined with the tuning word to allow control of phase? What is the range of allowed phase shifts?

ADIApproved · Accepted Answer

Hi Lionel - 
 1. and 2. From the data sheet: 
 
 TRIGGER Pin 
 A falling edge on the TRIGGER pin starts the generation of a pattern. If the RUN bit is set to 1, the falling edge of the TRIGGER pin starts the pattern generation. As shown in Figure 41, the pattern generator state goes to pattern on a number of CLKP/CLKN clock cycles following the falling edge of the TRIGGER pin. This delay is programmed in the PATTERN_DELAY bit field. The rising edge on the TRIGGER pin is a request for termination of pattern generation; see Figure 42. 
 A pattern can come from the DDS, the SRAM, or teh ramp generator. Or a combination of teh SRAm and DDS. 
 3. The tuning word prgrams the DDS output frequency. DDS_PHASE programs teh DDS output phase shift from 0 to 360 frgrees in .00549 degree steps. 
 Thanks, 
 Larry)

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Questions regarding AD9102 Trigger signal