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Chapter 2 119
Programming Fundamentals
C Programming Using VTL
vi This is a pointer to the session identifier for this
particular device session. This pointer will be used to
identify this device session when using other VTL
functions.
The following is an example of opening sessions with a GPIB
multimeter and a GPIB-VXI scanner:
ViSession defaultRM, dmm, scanner;
.
.
viOpenDefaultRM(&defaultRM);
viOpen (defaultRM, “GPIB0::22::INSTR”, VI_NULL,
VI_NULL, &dmm);
viOpen (defaultRM, “GPIB-VXI0::24::INSTR”, VI_NULL,
VI_NULL, &scanner);
.
.
viClose (scanner);
viClose (dmm);
viClose(defaultRM);
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:
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]