Keithley KPCI-3110, User Manual

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2-14 Functional Description KPCI-3110 and KPCI-3116 User’s Manual
The about-trigger acquisition starts when you start the operation. When the board detects the
selected post-trigger event, the board stops acquiring pre-trigger data and starts acquiring post-
trigger data.
If you are using internally-retriggered scan mode and the post-trigger event has not occurred, the
board continues to acquire pre-trigger data using the internal retrigger clock to clock the opera-
tion. If, however, the post-trigger event has occurred, the board continues to acquire post-trigger
data using the internal retrigger clock to clock the operation.
The about-trigger operation stops when the specified number of post-trigger samples has been
acquired, or when you stop the operation. Refer to
page 2-8 for more information on internally-
retriggered scan mode.
Figure 2-7 illustrates continuous about-trigger mode using a channel list of two entries: channel
0 and channel 1. In this example, pre-trigger analog input data is acquired on each clock pulse of
the A/D sample clock, scanning the channel list continuously, until the post-trigger event occurs.
When the post-trigger event occurs, post-trigger analog input data is acquired continuously on
each clock pulse of the A/D sample clock.
Figure 2-7
Continuous about-trigger mode
Figure 2-8 illustrates the same example using internally-retriggered triggered scan mode. The
multiscan count is 2 indicating that the channel-gain list will be scanned twice per trigger or
retrigger. In this example, pre-trigger analog input data is acquired on each clock pulse of the
A/D sample clock for two scans; then, the board waits for the internal retrigger event. When the
internal retrigger occurs, the board begins acquiring pre-trigger data until the post-trigger event
occurs. Then, the board finishes scanning the channel-gain list the specified number of times, but
acquires the data as post-trigger samples. On all subsequent internal retriggers, post-trigger data
is acquired.
Figure 2-8
Continuous about-trigger mode with triggered scan
Pre-trigger Event Occurs
Chan 0
Chan 1
Chan 0
. . .
A/D
Sample
Post-trigger Event Occurs
Pre-trigger Data Acquired Post-trigger Data Acquired
Chan 1
Chan 0
Chan 1
Chan 0
Chan 1
Chan 0
Chan 1
Chan 0
Chan 1
Pre-trigger event occurs;
pre-trigger data is
acquired for 2 scans of
the CGL.
Chan 0
Chan 1
Chan 0
Chan 1
A/D
Sample
Re-trigger event
occurs; pre-trigger
data is acquired until
post-trigger occurs.
Chan 0
Chan 1
Chan 0
Chan 1
Chan 0
Chan 1
Post-trigger event occurs;
post-trigger data is
acquired until the end of
the number of scans.
Re-trigger event occurs;
post-trigger data is
acquired for 2 scans of
the CGL.