User`s guide

Operation Theory • 39
Then
Acquisition sequence of channels: 1, 2, 0, 2, 1, 2, 0, 2, 1, 2, 0, 2.
Sampling Interval = 240/24M s = 10 us
Scan Interval = 960/24M s = 40 us
Equivalent sampling rate of ch0, ch1: 25kHz
Equivalent sampling rate of ch2: 50kHz
5.1.3.3 Trigger Modes
There are 5 trigger modes (software-trigger, pre-trigger, post-trigger,
middle-trigger, and delay-trigger) to start the data acquisition described in
5.3.1.1. All but software trigger are external digital triggers. An external digital
trigger event occurs when a rising edge or a falling edge (software
programmable) of a digital signal is detected on pin 46 of J1. They are
described as follows.
Software-Trigger Acquisition
This trigger mode does not need any external trigger source. The data
acquisition starts right after you execute the specified function calls to begin
the operation. The scan timing is the same as fig 9. The total acquired data
length = DIV_counter*SC_counter.
Pre-Trigger Acquisition
Use pre-trigger acquisition in applications where you want to collect data
before an external trigger event. The A/D starts when you execute the
specified function calls to begin the operation, and it stops when the external
trigger event occurs. Users must program the value M in the M_counter (16bit)
to specify the amount of stored scans of data before the trigger event. If the
external trigger occurs after M scans of data are converted, the program only
stores the last M scans of data, as illustrated in fig 10, where M_counter = M =3,
DIV_counter =4, SC_counter = 0. The total stored amount of data =
DIV_counter *M_counter =12.