General question for how the PCIe-6321 works...

[New_Ni_User]

I understand that the NI PCIe-6321 records digital input at 1000kS/s and analog input at 250kS/s. I'm now trying to make sure I understand how this card works when it's recording since it does not have synchronous recording. For Example: If I have 2 analog inputs and 2 digital inputs to this card and I'm using custom software to sample data on all channels at 4kS/s... would it work in the following way? T0 (0ms) = [Analog_channel#1_value] [0.008ms delay] [Analog_channel#2_value] [.008ms delay] [Digital_channel#1_value] [.002ms delay] [Digital_channel#2_value] [.002ms delay] [Pause until next sample] T1 (0.25ms) = [Analog_channel#1_value] [0.008ms delay] [Analog_channel#2_value] [.008ms delay] [Digital_channel#1_value] [.002ms delay] [Digital_channel#2_value] [.002ms delay] [Pause until next sample] T2 (0.5ms) = [Analog_channel#1_value] [0.008ms delay] [Analog_channel#2_value] [.008ms delay] [Digital_channel#1_value] [.002ms delay] [Digital_channel#2_value] [.002ms delay] If we then examine the data timepoints... Timepoint, Channel, Actual Recording Time (since start) ------------------------------------------------------- T0, Analog_channel#1_value, 0.000ms T0, Analog_channel#2_value, 0.008ms T0, Digital_channel#1_value, 0.016ms T0, Digital_channel#2_value, 0.018ms T1, Analog_channel#1_value, 0.250ms T1, Analog_channel#2_value, 0.258ms T1, Digital_channel#1_value, 0.266ms T1, Digital_channel#2_value, 0.268ms T2, Analog_channel#1_value, 0.500ms T2, Analog_channel#2_value, 0.508ms T2, Digital_channel#1_value, 0.516ms T2, Digital_channel#2_value, 0.518ms Thank you for any info!

[Dennis_Knutson]

Neither. From the analog input task, you would have acquired ai0 at t0. At t=14 us (inter-channel delay), ai1 is acquired. At t=.25 ms (1/sample rate), second ai0 sample. At t=.264 ms, the second ai1 sample. Etc.

The digital input is simple. That's a separate DAQmx read and it has a separate clock and you read all channels at once so there is entire record every .25 ms.