VXI VT1422A, VT1529A/B Setting up the Trigger System

Programming the VT1422A for Data Acquisition and Control 129Chapter 4
Setting up the Trigger System
Arm and Trigger
Sources
Figure 4-6 shows the trigger and arm model for the VT1422A. Note that
when the Trigger Source selected is TIMer (the default), the remaining
sources become Arm Sources. Using ARM:SOUR allows an event to be
specified that must occur in order to start the Trigger Timer. The default
Arm source is IMMediate (always armed).
Selecting the
Trigger Source
In order to start an instrument operation cycle, a trigger event must occur.
The source of this event is selected with the TRIGger:SOURce <source>
command. The following table explains the possible choices for <source>.
BUS
EXTernal
HOLD
IMMediate
TTLTrg<n>
SCP Trg
ARM/TRIGgerSource
TriggerSource Selector
ArmSource Selector
ARM:SOURce <source>
TRIGger:TIMer <interval>
Trigger
Timer
TIMer
Trigger
Enable
TRIGger:SOURce <source>
Internal
Trigger Signal
Trigger
Counter
TRIGger:COUNt <count>
Figure 4-6. Logical Arm and Trigger Model
Parameter Value Source of Trigger (after INITiate:… command)
BUS TRIGger[:IMMediate], *TRG, GET (for GPIB)
EXTernal "TRG" signal input on terminal module
HOLD TRIGger[:IMMediate]
IMMediate The trigger signal is always true (scan starts when an
INITiate:… command is received).
SCP SCP Trigger Bus (future SCP Breadboard)
TIMer The internal trigger interval timer (must set Arm source)
TTLTrg<n> The VXIbus TTLTRG lines (n=0 through 7)