AD5672R Daisy chain not working

Question

Hello 
 I'm currently working on daisy chaining 2 AD5672R DACs together, I've sent in the command(1000 and DB0=1) to enable the daisy chain mode but it doesn't seem to be responding to the command. I've attached a snap of the chipscope signals and i believe it is what is recommended on the datasheet. The first 8 writes are for the first AD5672R and the secnond 8(longer writes) are for the second AD5672R. could you please advice me on the normal process for daisy chaining these DACS. Also not seen in the pics is the LDAC is held low for the duration of the run any help would be great. 
 Thank you

isantos · Accepted Answer

Hi, 
 I really would like to help you and doing my best to do so. 
 
 From what i can see it seems that its getting the correct bits but not reacting for some reason, oh as a note all DACs seems to program if i do a write command(24 bits) to the first 8 DACs in the first chip then do an extra no op command at the end but that method doesn't have the control-ability that im looking for. I'm able to wrtie to the first chip and and change the values to any of the 8 DACs freely but am unable to get any reaction out of the second chip when trying to program only one DAC. 
 
 Does this mean that the main problem is that DAC_2 doesn't give the correct output even it received the command (as shown in PIC3 of your latest reply)? 
 Can you also try to set DAC_2 to daisy mode before sending the commands? 
 FRAME1: 24 bit setting DAC_1 to daisy mode 
 FRAME2: 48 bits total, most significant (left) 24 bit = daisy mode intended for DAC_2, least significant (right) 24 bit = NOP 
 FRAME3: 48 bits total, 
 most significant (left) 24 bit = 24 bit data for DAC_2, ( 0011 0000 100000000000 0000) 
 least significant (right) 24 bit = 24 bit data for DAC_1. ( 0011 0111 100000000000 0000) 
 
 Frames 4,5,6 can be similar to frame 3. 
 
 Can you try these please? 
 
 Cheers, 
 Ivan