AD9546 1Hz Output Duty Cycle Configuration

Question

Hi, 
 I have a system which contains AD9546 EVB. 
 I configured inputs and outputs and everything works fine. I am using an OCXO (10MHz) for reference. 
 
 But I want to change duty cycle for the all 1Hz outputs. 
 When I checked the datasheet, according to page 105, I understand that first I should get the "Q divider" value and make a calculation to get "Modulation Step". Then, I should write that values to the related registers. 
 However, when I read the value from registers of "Q Divider" using evaluation software, it returns hex "00". So I could not make the calculation. 
 Even If I tried to write random values to the register of both Q Divider and Modulation Step, nothing changed. 
 
 Is there any way to do that? 
 Thanks,

pminc48 · Accepted Answer

HI, 
 to change the duty cycle of an output, you need to reference section Output Pulse Width Control at page 98 in the AD9546 rev 0 data sheet. 
 I created OUT0A=1Hz with a Q0=1,225,500,000. 
 I then wanted to create a 80% duty cycle. I calculated a Phase offset=0.8*2*1,225,500,000=1,960,800,000. In the eval software, I selected Duty Cycle Adjust and in the Phase Control window I introduced 1960800000. I then clicked Load. I saw on the oscilloscope OUT0AP stayed high for 800ms and low for 200ms. So this worked. OUT0AN also changed its duty cycle accordingly. 
 I then looked with RegMap command into the register values and I found the registers 0x1108, 0x1107, ..., 0x1104 changed accordingly 
 
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AD9546 1Hz Output Duty Cycle Configuration