VXI manual VT1433B Triggering, trigger type, enabling function

VT1433B User's Guide

Using the VT1433B

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.

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