Chapter 4
Theory of Operation
©
National Instruments Corporation
4-35
NI PXI-4220 User Manual
Table 4-4.
PXI Trigger Bus Timing Signals
Signal
Direction
Description
Availability
on PFI0
SMB
Availability
on PXI
Trigger Bus
AI START TRIG
Input
Output
This is the source for the
analog input digital start
trigger, the trigger that begins
an acquisition.
This sends out the actual
analog input start trigger.
Input
Output
Input
Output
AI REF TRIG
Input
Output
This is the trigger that creates
the reference point between
the pretrigger samples and the
posttrigger samples.
Input
Input
Output
AI SAMP CLK
Input
Output
This clock controls the time
interval between samples.
Each time the sample clock
produces a pulse, one sample
per channel is acquired.
Input
Input
Output
AI CONV CLK
Input
Output
This clock directly causes
analog-to-digital conversions.
Input
Input
Output
AI PAUSE TRIG
Input
This signal can pause and
resume acquisition.
Input
Input
AI SAMPLE CLK
TIMEBASE
Input
This timebase provides the
master clock from which the
sample clocks are derived.
Input
Input
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