Size of the pre trigger window expressed in samples (10ns). The waveform buffer will start at this number of samples before the trigger point.


Pre Trigger (0x1n38, 0x8038, R/W, I)
Sets the Pre Trigger for the waveform acquisition. Once the event triggers, the digital samples are delayed by the pre trigger number of 
samples, to ensure that the waveform is completely acquired. 
Bit Description
[9:0] Number of samples Ns for the Pre Trigger width, where Pre Trigger =
     Ns * 2. The value is expressed in steps of sampling frequency, 10 ns.
[31:10] Reserved