Multiple Applications Using the NI-VISA Driver

Multiple-application support is an important feature in all implementations of the NI-VISA driver. You can have several applications that use NI-VISA running simultaneously. You can even have multiple instances of the same application that uses the NI-VISA driver running simultaneously, if your application is designed for this. The NI-VISA operations perform in the same manner whether you have only one application or several applications (or several instances of an application) all trying to use the NI-VISA driver.

However, you need to be careful when you have multiple applications or sessions using the low-level bus access functions. The memory windows used to access the bus are a limited resource. Call the viMapAddress() operation before attempting to perform low-level bus access with viPeekXX() or viPokeXX(). Immediately after the accesses are completed, always call the viUnmapAddress() operation so that you free up the memory window for other applications.