Agilent Technologies E4406A VSA manual Device Sessions, viOpen sesn, rsrcName, accessMode, timeout

	Programming Fundamentals
	C Programming Using VTL
	All devices that you will be using need to be connected and in working
NOTE
	condition prior to the first VTL function call (viOpenDefaultRM). The
	system is configured only on the first viOpenDefaultRM per process.
	Therefore, if viOpenDefaultRM is called without devices connected and
	then called again when devices are connected, the devices will not be
	recognized. You must close ALL resource manager sessions and re-open
	with all devices connected and in working condition.
	Device Sessions
	There are two parts to opening a communications session with a
	specific device. First you must open a session to the default resource
	manager with the viOpenDefaultRM function. The first call to this
	function initializes the default resource manager and returns a session
	to that resource manager session. You only need to open the default
	manager session once. However, subsequent calls to viOpenDefaultRM
	returns a session to a unique session to the same default resource
	manager resource.
	Next, you open a session with a specific device with the viOpen
	function. This function uses the session returned from
	viOpenDefaultRM and returns its own session to identify the device
	session. The following shows the function syntax:
	viOpenDefaultRM (sesn);
	viOpen (sesn, rsrcName, accessMode, timeout, vi);
	The session returned from viOpenDefaultRM must be used in the sesn
	parameter of the viOpen function. The viOpen function then uses that
	session and the device address specified in the rsrcName parameter to
	open a device session. The vi parameter in viOpen returns a session
	identifier that can be used with other VTL functions.
	Your program may have several sessions open at the same time by
	creating multiple session identifiers by calling the viOpen function
	multiple times.
	The following summarizes the parameters in the previous function
	calls:
	sesn	This is a session returned from the viOpenDefaultRM
		function that identifies the resource manager session.
	rsrcName	This is a unique symbolic name of the device (device
		address).
	accessMode	This parameter is not used for VTL. Use VI_NULL.
	timeout	This parameter is not used for VTL. Use VI_NULL.

118 Chapter 2