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Chapter 3      Software Overview

© National Instruments Corporation

3-41

NI-VXI User Manual

GetSignalHandler

 returns the address of the current signal handler

for the specified VXI logical address. If signal interrupts are enabled
(via 

EnableSignalInt

), the signal handler for a specific logical

address is called if the 

RouteSignal

 function has been set up to route

signals to the handler (as opposed to the global signal queue). The

InitVXIlibrary

 function automatically installs a default handler,

DefaultSignalHandler

, for every VXI logical address.

RouteSignal

 specifies how to route VXI signals for the application.

Two methods are available to handle VXI signals. You can handle the
signals either at interrupt service routine time or by queueing on a
global signal queue. For each VXI logical address, the 

RouteSignal

function specifies which types of signals should be handled by the
handlers, and which should be queued on the global signal queue. A
separate handler can be installed for each VXI logical address present
(see the description of 

SetSignalHandler

). The 

InitVXIlibrary

function automatically installs a default handler,

DefaultSignalHandler

, for every VXI logical address. If signals

are queued, the application can use the 

SignalDeq 

or

WaitForSignal

 function to selectively return a signal off a global

signal queue by VXI logical address and/or type of signal. The default
for 

RouteSignal

 is to have all signals routed to interrupt service

routines.

SetSignalHandler

 replaces the current signal handler for the

specified VXI logical address with an alternate handler. If signal
interrupts are enabled (via 

EnableSignalInt

), the signal handler for

a specific logical address is called if the 

RouteSignal

 function has

been set up to route signals to the handler (as opposed to the global
signal queue). The 

InitVXIlibrary

 function automatically installs a

default handler, 

DefaultSignalHandler

, for every VXI logical

address. The logical address (la) value of -2 is a special case and is
provided to specify a handler to capture signals from devices not
known to the device information table. This should occur only when
the local CPU is not the Resource Manager or VME devices not listed
in the Non-VXI Device Editor in 

VXIedit

. Support is not provided to

handle these signals via the global signal queue or the

WaitForSignal

 function.