Specifications

Programming the
Trigger Timer
When the VT1419A is triggered, it begins its algorithm execution cycle. The time it
takes to complete a cycle is the minimum interval setting for the Trigger Timer. If
programmed to a shorter time, the module will generate a “Trigger too fast” error.
How can this minimum time be determined? After all algorithms are defined, send
the ALG:TIME? command with its <alg_name> parameter set to ‘MAIN.’ This
causes the VT1419A’s driver to analyze the time required for all four phases of the
execution cycle: Input, Update, Execute Algorithm, and Output. The value returned
from ALG:TIME? ‘MAIN’ is the minimum allowable Trigger Timer interval. With
this information, execute the TRIGger:TIMer <interval> command and set
<interval> to the desired time that is equal to or greater than the minimum.
Setting the Trigger
Counter
The Trigger Counter controls how many trigger events will be allowed to start an
input-calculate-output cycle. When the number of trigger events set with the
TRIGger:COUNt command is reached, the module returns to the Trigger Idle State
(needs to be INITiated again). The default Trigger Count is 0 which is the same as
INF (can be triggered an unlimited number of times). This setting will be used most
often because it allows un-interrupted execution of control algorithms.
To set the trigger count to 50 (perhaps to help debug an algorithm):
TRIG:COUNT 50 execute algorithms fifty times
then return to Trig Idle State.
Outputting Trigger
Signals
The VT1419A can output trigger signals on any of the VXIbus TTLTRG lines. Use
the OUTPut:TTLTrg<n>[:STATe] ON | OFF command to select one of the
TTLTRG lines and then choose the source that will drive the TTLTRG line with the
command OUTPut:TTLTrg:SOURce command. For details, see OUTP:TTLTRG
commands starting on page 249.
To output a signal on the TTLTRG1 line each time the Trigger Timer cycles
execute the commands:
TRIG:SOUR TIMER select trig timer as trig source
OUTP:TTLTRG1 ON select and enable TTLTRG1 line
OUTP:TTLTRG:SOUR TRIG each trigger output on TTLTRG1
Programming the VT1419A Multifunction
Plus
Setting up the Trigger System
Chapter 3 79
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