Can a Pretriggered Analog Acquisition be Continuous?

Issue Details

When I start my acquisition, I would like to acquire a continuous amount of pretrigger data over an analog threshold until my reference trigger occurs to stop my acquisition. For example, I want to use a trigger source to acquire pre and post triggered data with respect to this trigger time. e.g., when I give a trigger, 100 samples after the trigger, as well as 10 samples before the trigger, will all be recorded in a buffer. 

In essence, I would like to perform a continuous acquisition with a reference trigger. Can I do this?

Solution

Pretriggered acquisitions are ultimately finite acquisitions, but data that is written to the buffer can be read continuously until the reference (stop) trigger occurs and the acquisition completes.  When the acquisition begins (either from a software or hardware start trigger), data writes to the buffer in a circular fashion. 

In a normal pretriggered acquisition, if the buffer has become full and the reference trigger has not yet occurred, the data in the buffer is overwritten. However, while the acquisition is still in progress, data can be read from the buffer before it is overwritten, resulting in the acquisition running like a continuous operation.