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Chapter 3      Software Overview

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NI-VXI User Manual

crosspoint switch configurator (depending on the hardware capabilities
of the applicable device).

UnMapTrigToTrig

 unconfigures triggering hardware that was

configured by the 

MapTrigToTrig

 function to route specified source

trigger locations to destination trigger locations.

The NI-VXI source trigger functions act as a standard interface for
asserting (sourcing) TTL and ECL triggers, as well as for detecting
acknowledgments from accepting devices. These functions can source
any of the VXI-defined trigger protocols from the local embedded
controller or external extended controller(s). You can use the 

SrcTrig

function to initiate any of the trigger protocols. If the protocol requires
an acknowledgment and your application is required to know when the
acknowledgment occurs, you must use the 

SetTrigHandler

 function

to install a callback handler for the specified trigger line. A default
handler, 

DefaultTrigHandler

, is installed for each one of the

trigger lines when 

InitVXIlibrary

 is called. You can use the

SetTrigHandler

 function at any time to replace the default handlers.

Use 

SrcTrig

 to source any one of the VXI-defined trigger protocols

from the local CPU or from any remote frame extender device
that supports trigger assertion. For protocols that require an
acknowledgment from the accepting device (ASYNC or SEMI-SYNC),
you need to specify whether to wait for an acknowledgment (with a
timeout) or return immediately and let the trigger handler get called
when the acknowledgment is received. Another option is available in
which you can assert or unassert any of the trigger lines continuously,
or have an external trigger (possibly from the front panel) routed to the
VXIbus backplane.