VXI VT1433B, User Manual, Page: 101 / 203

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. Which one
of the eight TTL trigger line is chosen by e1432_get_ttltrg_lines().
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 e1432_set_auto_trigger()
the e1432_trigger_measure() function e1432_trigger_measure()
a source trigger e1432_set_trigger_channel()
a tach trigger e1432_set_trigger_channel()
an external trigger e1432_set_trigger_ext()
an input level or bound trigger event
e1432_set_trigger_channel()
and e1432_set_trigger_mode()
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 e1432_set_auto_trigger() the setting E1432_MANUAL_ARM 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 e1432_init_measure() function
connects the VT1433B trigger lines to the VXI backplane and at that point, the
selection of which TTL trigger lines through e1432_get_ttltrg_lines() 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
The Host Interface Library
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