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Chapter 5
PCI-1712/1712L User’s Manual
Advantech Co., Ltd.
www.advantech.com
w Set to About-Trigger Acquisition Mode
w The sample clock source and sample rate
w The trigger source and edge type
w The total acquired sample number N
w The specific sample number M before the trigger event. The range
of preset sample number is 2 samples minimum and is limited on
basis of memory size of your host PC.
In about-trigger mode, users must first designate the size of the
allocated memory and the amount of samples to be snatched after the
trigger event happens. The about-trigger acquisition starts when the
first clock signal comes in. Once a trigger event happens, the on-going
data acquisition will continue until the designated amount of samples
have been reached. When the PCI-1712/1712L detects the selected
about-trigger event, the card keeps acquiring the preset number of
samples, and kept the total number of samples on the FIFO.
Figure 5-3: About-Trigger Acquisition Mode
q Pre-Trigger Acquisition Mode
Pre-Trigger mode is a particular application of about-trigger mode. Use
pre-trigger acquisition mode when you want to acquire data before a
specific trigger event occurs. Pre-trigger acquisition starts when you
start the operation and stops when the trigger event happens. Then
the specific number of samples will be reversed in the FIFO before the
pre-trigger event occurred. Please specify the following parameters,
when using software in Pre-trigger acquisition mode:
w Set to Pre-Trigger Acquisition Mode
w The sample clock source and sample rate
w The trigger source and gate type
w Assume the total acquired sample number is N, then set the total
sample number to be N+2.
Trigger Event
Acquired number of
samples M after trigger
event happened
Total Acquired sample number: N
t
N-M N
1 2 3