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Annex
NRP2
359
User Manual 1173.9140.02 ─ 07
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
Table 1-4: Communications channels of a VXI11 connection
Channel
Meaning
Core
All communications between client and server are handled via this channel, with the excep-
tion of abort and interrupts.
Abort
Since the commands in the core channel are serialized and therefore cannot be interrup-
ted, asynchronous abort commands must be handled via a separate, independent channel.
This channel has no other tasks.
Interrupt
Service requests (SRQ) are signaled via this channel to the network instrument client. As
this channels is shared by all links, the client must determine which device has triggered
the SRQ by querying the status bytes (function device_readstb()) of all connected devices.
A.2.2.2
Connection setup
A socket connection is set up for each channel. All commands via the core or abort
channel contain an ID that is used to assign the command to a link. The interrupt chan-
nel, which is also implemented using sockets, is shared by all links. Commands trans-
mitted via this channel do not contain a link ID. The setup is handled by the network
instrument client, which first requests the connections from the network instrument
server's portmapper service at port 111. The portmapper subsequently activates the
channel in the R&S
NRP2 and tells the client at which ports channel services can be
addressed. For this reason, it is important that any firewalls or routers between the cli-
ent and the R&S
NRP2 enable free access from the controller to the R&S
NRP2 (core
and abort channels) and vice versa (interrupt channel). As the ports for the channels
are dynamically assigned, reliable information regarding the port numbers used cannot
be provided.
A.2.2.3
Remote control via VXI11
The following possibilities are suggested for remote-controlling the R&S
NRP2 via
VXI11:
●
The simplest way to create remote-control programs is by using a virtual instru-
ments software architecture (VISA) implementation and creating the remote-control
programs under Visual Basic or C/C++. VISA implementations provide an applica-
tion programming interface (API) that offers all necessary functions. Knowledge
about VXI11 is helpful but not required. The VISA resource identifier used to iden-
tify a VXI11 device has the following format: TCPIP::<IP address>::INSTRThe IP
address is specified using the familiar dot notation (e.g. 89.10.65.59).
–
TCPIP::<IP address>::INSTR
Remote control interfaces
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