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VX4101A MultiPaq Instrument User Manual
2–9
About Instrument Triggering
For digital multimeters, scanners, and sources such as the DAC and Digital I/O,
it is common to think of the devices as triggering to start an operation. For
counters, on the other hand, it is more common to think of the counter as arming
to take a measurement.
Triggering and arming the VX4101A and its associated instrument modules can
be considered to be the same operation. Any differences will be noted. For
example, in addition to the STARt arming source, the Counter implements a
STOP arming source. Counting is enabled when the start source is asserted and
disabled when the stop source is asserted.
Trigger Sources
For the SurePatht master control, triggers are implemented in firmware, while
for the other instruments, the triggers are implemented in hardware. For this
reason, the SurePatht timers have less resolution and accuracy than the other
instrument triggers. Since the SurePatht trigger times are of the same order as
typical settling delays, impact to instrument performance is negligible.
Table 2–1: VX4101A Global Trigger Sources
Trigger Source
HOLD Instrument trigger source is disconnected from all trigger sources. If
you INITiate an instrument with a trigger source of HOLD, the
instrument will only enter the triggered state upon receipt of a
TRIGger:IMMediate command. This trigger is fixed.
IMMediate Device enter the triggered state immediately after receiving the INITiate
command. This trigger is fixed.
BUS Trigger source is either a word serial trigger command or the 488.2
common command *TRG. This trigger is delayable.
EXTernal This trigger source is derived from the front panel MultiPaqt External
Trigger In, Pin24B signal. This input signal is common to all
instruments. This trigger is delayable.
TTLTrigger<0-7> One of the VXIbus TTL trigger lines. This trigger is delayable. TTLT
sources cannot be routed to other TTLT sources.
COMMand<0-4> One of five software command triggers. TRIG:FIR<N> is used to send
these triggers. This trigger is delayable.
TIMer Trigger source is the programmable periodic timer. This trigger is fixed.
SUREPATH Trigger is generated whenever a scan line has switched and settled.
This trigger is delayable.