Do you mean you want to install a non-National Instruments device in the PXI chassis and use it under the LabVIEW Real-Time operating system?
Beginning with LabVIEW RT version 6, VISA is supported and will allow programmers to create third-party instrument drivers with register-level programming. Register-based communication with devices is usually accomplished via reads and writes to registers. VISA has the ability to read from and write to individual device registers, as well as a block of registers, through the Memory I/O Services. In addition to accessing register-based devices, VISA also provides support for memory management of the memory exported by a device. For example, both local controllers and remote devices can have general-purpose memory in A24/A32 space. With VISA, although the user must know how each remote device accesses its own memory, the memory management aspects of local controllers are handled through the Shared Memory functions in VISA. Please refer to the NI-VISA User Manual (http://digital.ni.com/manuals.nsf/7aba4d4ed8d9fa958625663500505c98/3eb071c781b671ca8625665e00676c3d) and NI-VISA Programmer Reference Manual () for more information on creating register-level device drivers with VISA (http://digital.ni.com/manuals.nsf/7aba4d4ed8d9fa958625663500505c98/c896da28c1f03187862568ab006a4ede).
In terms of using VISA, you will have to create a driver file using the PXI Driver Development Wizard that installs with NI-VISA.
This is from the readme file that installs with VISA 2.5:
"To perform register based VISA communication, first you need to generate a .INF file using the PXI wizard for your device. The wizard is at Start>>Programs>>National Instruments>>VISA>>PXI Driver Development Wizard. For high-level access, use the viInXX/viOutXX operations. For low-level access, use viMapAddress(), then useviPeekXX/viPokeXX operations to perform register accesses. The online help provides details on these operations. The help is at Start>>Programs>>National Instruments>>VISA>>VISA Help. The PXI wizard can also be used to enable PCI interrupt support for your device. For more information, visit www.ni.com/visa"
