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102 Chapter 3
Programming Examples
C Programming Examples using VTL
The above function first opens a session with the default resource manager. The
session returned from the resource manager and a device address is then used to
open a session with the GPIB device at address 22. That session will now be
identified as dmm when using other VTL functions. The session returned from the
resource manager is then used again with another device address to open a session
with the GPIB/VXI device at primary address 9 and VXI logical address 24. That
session will now be identified as scanner when using other VTL functions. See the
following section for information on addressing particular devices.
Addressing a Session
As seen in the previous section, the rsrcName parameter in the viOpen function is
used to identify a specific device. This parameter is made up of the VTL interface
name and the device address. The interface name is determined when you run the
VTL Configuration Utility. This name is usually the interface type followed by a
number. The following table illustrates the format of the rsrcName for the different
interface types:
The following describes the parameters used above:
board This optional parameter is used if you have more than one
interface of the same type. The default value for board is 0.
VXI logical
address This is the logical address of the VXI instrument.
primary
address This is the primary address of the GPIB device.
secondary
address This optional parameter is the secondary address of the GPIB
device. If no secondary address is specified, none is assumed.
INSTR This is an optional parameter that indicates that you are
communicating with a resource that is of type INSTR, meaning
instrument.
NOTE If you want to be compatible with future releases of VTL and VISA, you must
include the INSTR parameter in the syntax.
The following are examples of valid symbolic names:
VXI0::24::INSTR Device at VXI logical address 24 that is of VISA type INSTR.
Interface Syntax
VXI VXI [board]::VXI logical address[::INSTR]
GPIB/VXI GPIB-VXI [board]::VXI logical address[::INSTR]
GPIB GPIB [board]::primary address[::secondary address][::INSTR]