VXI VT1433B - Manual (Page 68)

VT1433B Triggering
The following is a short discussion of triggering for the VT1433B.
Triggering is defined as the transition from the armed state to the triggered state.
This transition is caused by a low going edge on a TTL trigger line. The
function hpe1432_getTtltrgLines selects which of the eight TTL trigger lines is to
be used.
The low-going transition of the TTL trig line can be caused by any of the
following items:
trigger type enabling function
the AUTO TRIGGER circuitry hpe1432_setAutoTrigger
the hpe1432_triggerMeasure function hpe1432_triggerMeasure
a source trigger hpe1432_setTriggerChannel
a tach trigger hpe1432_setTriggerChannel
an external trigger hpe1432_setTriggerExt
an input level or bound trigger event
hpe1432_setTriggerChannel
and hpe1432_setTriggerMode
Each of these trigger sources can be enabled or disabled independently, so quite
complex trigger setups are possible. In all cases, however, the first trigger event
kicks off the measurement and the following trigger events become superfluous.
Note that for hpe1432_setAutoTrigger the setting HPE1432_MANUAL_TRIGGER
really means “don’t auto trigger” not “expect a manual trigger”.
For single-VT1433B systems, the TTL trigger signal is not connected to the VXI
backplane. For multiple VT1433B systems, the hpe1432_initMeasure function
connects the VT1433B trigger lines to the VXI backplane and at that point, the
selection of which TTL trigger lines through hpe1432_getTtltrgLines is relevant.
Multiple mainframe systems will need to account for the unidirectional nature of
the inter-mainframe MXI extenders which will prevent all but the “upstream”
mainframe from triggering the system.
VT1433B User's Guide
Using the VT1433B
3-30