HSDIO is different from DAQ. The architecture of HSDIO memory is not same as regular DIO card.
If you look at any HSDIO examples, you will find that you are waiting for reference trigger. This will be software/hardware.
The HSDIO will be waiting for reference trigger, but it will be continuously acquiring data and filling the deep onboard memory inside the HSDIO while waiting for trigger.
These high speed cards are usually used to transmit bursts of data depending on the user application. Even the scopes are also designed in that way. Because PC cannot read the data into it's RAM at the rate which HSDIO's normally operate such as 100MHZ.
When an event (trigger) occurs, you can transfer the data but still you will be clocking/sampling data at faster rates.
If you look at the memory architecture of HSDIO, it is continuously filling the buffer (record). But it stops filling the buffer, once it gets reference trigger.
You can also perform multi-record triggering and store 1000's of waveforms on the onboard memory. So, think of onboard memory being divided into small circular buffers (records). Once you get a trigger, it advances to next record. While the second record is being filled up, you can transfer the data to LabVIEW from the first record by cheesing the number of records available.So, basically High speed devices are used to capture transient events. But we can fool the driver by never sending the trigger. So, HSDIO will continuously storing the data into buffer. Then we transfer the data into ADE in the background. This is done for lower rates than full speed of the board without overflowing buffer.