R&S NRP2, User Manual

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Remote control interfaces
R&S
®
NRP2
353 User Manual 1173.9157.02 ─ 03
A.2.1 VXI11 protocol
The VXI11 protocol uses ONC RPC (open network computing remote procedure calls),
making it possible to call R&S
NRP2 functions at the source code level as if they were
running locally on the controller. The table below shows the relationships of the relevant
protocol layers in the OSI reference model.
Application VXI11 Network Instrument
Presentation XDR (Data representation)
Session ONC RPC
Transport TCP
Network IP
Data Link Ethernet/802.3
Physical 10/100BASE-T
Fig. 1-3: The VXI11 protocol stack in the OSI reference model
A VXI11 remote-control connection consists of three channels (core, abort and interrupt),
which can be used to set up as many links as desired. The concept of links makes it
possible to connect a network instrument client in a controller with several logical devices
in a host computer via a single VXI11 remote-control connection. A link is then set up to
each logical device. It is also possible to set up several links to one logical device, pro-
vided that several servers are running on the network instrument host or a network
instrument client is operated by several controllers. To prevent problems caused by sev-
eral controllers simultaneously accessing one device, links can be locked. In this case,
access via other links is not possible. An exception is an abort via the abort channel,
which can be executed at any time and also aborts the execution of commands via other
links.
Core Channel
Abort Channel
Interrupt Channel
Link 1
Link 2
Link n
Link 1, Link 2, Link n
Network
Instrument
Client Controller
Network Instrument Host
Link 1
Link 2
Link n
Link 1, Link 2, Link n
Network
Instrument
Server
R&S NRP : Network Instrument Host
Device
Fig. 1-4: Diagram of a VXI11 connection with several links
Ethernet