You're not answering the questions very clearly. However: I assume you're using a microcontroller to output data to the DAC and to read from the ADC. This microcontroller cannot write data and read data at the same time. Physically, because the bus can either be in write or in read mode, not both at the same time. Logically, because the program will run sequentially within the microcontroller.
So you will always have a delay between writing to the DAC and reading from the ADC.
If you really need 0 delay (exactly simultaneous read and write), then you will need additional hardware:
- 1 register to write the new DAC value into. This register will store the new value, but not latch it to its output until triggered by a separate signal.
- 1 register to read ADC data from
- 1 control signal that activates the output of the write register and the input of the read regaister at the same time
Of course you will need other types of DAC and ADC, too, since the ones you have chosen are serial and cannot be operated in this way.
To be able to judge your requirement for "simultaneous" output and input, we'd need tp know more about the DUT. What is the reason for your requirement? What happens, if you have a constant delay between writing to the DAC and reading from the ADC?