User`s manual

20 Operation Theory
Please refer to Table 4-3 for a brief summary on Trigger Modes
and their Trigger Sources.
Scan Timing and Procedure
There are 4 counters that need to be specified prior to program-
mable scans:
Trigger Mode Description
Trigger
Sources
Post-Trigger Perform a scan right after the trigger occurs.
Software Trigger
Digital Trigger
Analog Trigger
SSI AD Trigger
Delay-Trigger
Scan delayed by the amount of time pro-
grammed after the trigger
Post/Delay-
Trigger with
Retrigger
Perform repeated scan while trigger occurs
and it could be under Post-Trigger or De-lay-
Trigger mode.
Table 4-3: Trigger Modes and Corresponding Trigger Sources
Counter Name Width Description Notes
SI_counter 24-bit
Scan Interval, which
defines the interval
between each scan.
Scan Interval = SI_counter
/ Time-base*
SI2_counter 24-bit
Sampling Interval, which
defines the interval
between each sampled
channel.
Sampling Interval =
SI2_counter / Timebase*
PSC_counter 24-bit
Post Scan Counts, which
defines how many scans to
be performed with re-spect
to each trigger.
Delay_counter 16-bit
Define the delay time for
scan after trigger.
Delay Time =
(Delay_counter / Time-
base*), Timebase*=40M for
DAQ/PXI-2500 Series
Table 4-4: Summary of Counters for Programmable Scan