Hello everybody, my goal is to generate two digital output (DO) signals with finite samples. The thing is that they have to start at the same time and after N-samples they have to end at the same time as well. The first DO signal is a clock signal. The second DO signal is the digital data signal. In my application i have a daisy chain of 16 shift registers each storing 8 Bits which requires a total of 16*8=128 Bits digital data output signal. With my DO clock signal i will push the 128 Bits data signal to the shift register chain, one Bit at each rising edge of the clock . The clock has to start and stop exactly at the same time with the digital data signal otherwise data will thrown away from the shift register daisy chain. I used another main clock signal to trigger (with DAQmx Start Trigger Digital Edge) both my clock DO signal and digital data DO signal so they start at the same time but it didn't help. Sometimes the data signal starts before the clock signal or vice versa. How can i ensure that both signals (my digital clock output signal and digital data output signal) start and end fully synchronised which means starting/stopping at the exact same time everytime. What am i doing wrong, how can i change my VI to achieve this goal ? Some details about my VI: The while-loop on the top gets the data for digital data output signal from the user so it is not relevant for the problem i have. After the user sets the data which is going to be pumped to the shift register daisy chain, the generation of the output signals happens inside a Flat Sequence Structure. I am using: LabVIEW 17.0.1f3 (64-Bit) Hardware -> NI PXIe-1073 with NI PXIe-6358 Any help is highly appreciated. Best regards, Ecafer

LabVIEW

Starting/ending two digital output signals with finite samples exactly at the same time

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The main problem is that you're ignoring the advice both GerdW and I gave that you MUST put BOTH digital lines in the SAME task. There's only one hardware timing subsystem available for DO, any digital signals that you want to generate with clock-based timing must be in the one task that defines the timing.

Instead of 2 separate tasks, put both lines in one task and define your digital waveform to include both lines.

There aren't useful default values in your controls to determine whether you're also being careful to stagger your clock and data transitions so that your data is stable when the active clock edge arrives. But that'll likely be pretty important too.

-Kevin P

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