National Instruments NI-VXI - Manual (Page 78)

Chapter 3 Software Overview
NI-VXI User Manual 3-40 © National Instruments Corporation
returned immediately to the caller and the process/function is not
suspended.
The following paragraphs describe the VXI signal functions and
default handler. The descriptions are presented at a functional level
describing the operation of each of the functions. The functions are
grouped by area of functionality.
DefaultSignalHandler (signal)
DefaultSignalHandler is the sample handler for VXI signals that
is installed when the InitVXIlibrary function is called for every
applicable VXI logical address. The default handler performs no action
on the signals except when Unrecognized Command Events are
received. For these events, it calls the function
WSabort with an
abortop of UnSupCom to abort the current Word Serial transfer in
progress.
DisableSignalInt ()
DisableSignalInt desensitizes the application to local signal
interrupts. While signal interrupts are disabled, a write to the local
CPU VXI Signal register does not cause an interrupt on the local CPU;
instead, the local CPU hardware signal FIFO begins to fill up. If the
hardware FIFO becomes full, bus errors will occur on subsequent
writes to the Signal register. This function is automatically called when
the global signal queue becomes full, and is automatically re-enabled
on a call to
SignalDeq . DisableSignalInt along with
EnableSignalInt can be used to temporarily suspend the generation
of signal interrupts.
EnableSignalInt ()
EnableSignalInt sensitizes the application to local signal interrupts.
When signal interrupts are enabled, any write to the local CPU VXI
Signal register causes an interrupt on the local CPU. The internal signal
router then routes the signal value to the handler or to the global
signal queue, as specified by the
RouteSignal function.
EnableSignalInt must be called after InitVXIlibrary to
begin the reception of signals. Calls to RouteSignal and/or
SetSignalHandler must be made before the signal interrupt is
enabled to guarantee proper signal routing of the first signals.