Acquisition Onboard Memory

When an acquisition operation is initiated, the device begins waiting for the Start trigger. Once the Start trigger is received, the device starts acquiring data and storing the samples into device memory. The first sample acquired marks the beginning of the acquired record, as shown in the following figure.

If no Start trigger has been configured, acquisition begins immediately after the operation is initiated.

After the device has recognized the Start trigger and has acquired the configured number of pretrigger samples, the device can now recognize a Reference trigger. While waiting for the Reference trigger, the device is still sampling data into the device memory. If the record overflows, the newest samples overwrite the oldest samples in the record. After the Reference trigger is received, the device acquires enough posttrigger samples and finishes the acquisition, as shown in the following figure.

If no Reference trigger has been configured, a single record of data is acquired.

Fetching Acquired Data

Data acquired between the Start trigger and the first pretrigger sample is also available to be fetched. The following figure shows the four common fetch positions.

In cases where no Reference trigger has been configured, First Pretrigger Sample and Reference Trigger are equivalent to First Sample.

Multirecord Acquisitions

In the case of multirecord acquisitions, the Advance trigger initiates the acquisition or fetch operation for the second and all subsequent records. Therefore, for multirecord acquisitions, the Start trigger shown in the previous figures would be replaced by an Advance trigger for all records after the initial acquisition.