User manual

29 Chapter 4
4.2.2 Pacer Acquisition Mode
Use pacer acquisition mode to acquire data if you want to accurately con-
trol the time interval between conversions of individual channels in a
scan. A/D conversion clock comes from A/D counter or external clock
source on connector. A/D conversion starts when the first clock signal
comes in, and will not stop if the clock is still continuously sending into
it. Conversion data is put into the A/D FIFO. For high-speed data acquisi-
tion, you have to use the DMA data transfer for analog input to prevent
data loss.
4.2.3 Post-Trigger Acquisition Mode
Post-trigger allows you to acquire data based on a trigger event. Posttrig-
ger acquisition starts when the PCIE-1744 detects the trigger event and
stop when the preset number of post-trigger samples has been acquired or
when you stop the operation. This trigger mode must work with the DMA
data transfer mode enabled. Use post-trigger acquisition mode when you
want to acquire data when a post-trigger event occurs. Please specify the
following parameters after Post-Trigger Acquisition Mode has been set.
• The A/D sample clock source and sampling rate
• The trigger source
• The acquired sample number N
Figure 4.1: Post-Trigger Acquisition Mode